View Full Version : Back to buisness....Cooling problems on subaru engine

srn4 - n/a
4-Jun-06, 12:09 PM
I am having some serious problems keeping my subaru engine cool....It takes about 20 mins to get up to 110 degrees...

I have a nissan micra radiator sitting directly infront of the main fan.

I cant see any reason why I am getting so hot!

Ian suggested that perhaps the Micra has a more powerfull pump and therefore the radiator is more restrcitive than the origional Subaru one, hence not enough coolant is flowing?!?!

My temperature guage is an aftermarket one with the correct sender and I have no reason to belive that it is faulty.

The waterpump has been taken appart and cleaned and reassembled with new gaskets and spins freely.

Does anyone have any ideas? I cant really go for a long cruise if I have to stop every 20 mins to let it cool down!


andycollins - n/a
4-Jun-06, 03:00 PM
Hi Dunc,

Check the guage/sender by dipping the sender in to boiling water and see what it says.

Make sure the rad is clear of crud.



srn4 - n/a
4-Jun-06, 04:05 PM
Yes, boiling water and a thermometer....Why on earth didnt I think of that....

Paul Fitz - n/a
4-Jun-06, 04:46 PM
Duncan, Most car radiators come with a pressure relieving valve within the radiator cap. These can vary in pressure. It is possible that the radiator you have used, uses a different rated pressure cap as standard from the original Subaru type. Assuming of course that you have fitted a pressure cap!! http://hovercraft.org.uk/images/icons/smiley_icons/icon_surprised.gif)

srn4 - n/a
4-Jun-06, 05:05 PM
Yes I have a pressure cap in the rad. At about 115 degrees C it allows the radiator to boil over...

Irish Falcon - n/a
4-Jun-06, 05:53 PM

Looks like you have a basic cooling fault, check thermostat, most important check for air locks in system ,check all vent pipes are clear (if there are any),check circulation, check rad for muck both outside AND inside. As mention check pressure cap, however you should have enough spare cooling capacity to work without one. Philip

srn4 - n/a
4-Jun-06, 06:54 PM
Is it possible that the rad is too restrictive on the circulation pump?

My temp sender is outside the thermostat valve so the valve must be opening??!?!....Should I just pull the valve out and bin it?

How do you check for airlocks in the system?

Mart366 - n/a
4-Jun-06, 07:41 PM
do not remove the thermostat in an attempt to cure cooling problems,

if i recall dunc I and many others told you many months ago, you would have issues with cooling, looking at your setup.

going back to basics now.

the rad needs to be sufficient in size to alow adequate cooling capacity for your engine, therefore a nissan micra rad might fit or look good, but if it dosent offer the required amount of cooling then nothing will stop the engine from boiling over.

You say youve stripped and checked the pump, have you ascertained it actualy pumps??? it may turn, but if the impellor is badly worn, it may not be moving enough water..

and the most important, did you fit a kenlowe or similar fan to aid cooling??? you dont have the airflow a car has over the rad, ie a 70 mph flow force cooling the engine, therfore you need forced cooling. if as i suspect, you havent got a fan, as scoobys have an electric fan which is driven by a thermostatic switch, this again could be defective.

go and buy a cheap electric fan from breakers yard, attach it with zip ties and run it to your battery, turn it on so its perminantly running then go for a spin. if it overheats, then you need to look elwhere for your concern, (airlock, cylinder head crack, etc)


srn4 - n/a
4-Jun-06, 09:02 PM
Hey Mart.

I moved the radiator ages ago, no electric fan is going to help!


I will check over the pump again allong with everything else and see if I cant get to the bottom of this!

Paul Fitz - n/a
4-Jun-06, 09:13 PM
Which it might do if the wrong pressure.

Is the cap the original Subaru cap or is it working at the same pressure i.e. 108KPa (1.08 Bar or 15.66PSi nominal)

You must establish that the system is working at the correct pressure before you look for other causes if it is not the obvious, eg, air locks, leaks, kinked or blocked hoses etc.

Irish Falcon - n/a
4-Jun-06, 09:32 PM
I agree with Mart, go to basics. Remove and check thermostat, boil it up in a pot of water, check that it opens fully, if you have a spare try it, as Mart says do not run without one. Usually water pumps work once they rotate, very very unusual to see one thats too worn. I'm not too concerned about the size of your rad or the airflow through it, car rads are often big enough to cool at 15-20 MPH. You could try as Mart says and fit a lecy fan( maybe from the Micra?) Cant see from your pic if the rad is plumbed correctly, is the rad connected the right way round. Also some water will be lost from your rad when hot as I cant see any expansion tank fitted. Have a look in a Scooby to see the installation. Dont worry I'v see these promlems before in much bigger machinery, its usually something simple. Philip

srn4 - n/a
4-Jun-06, 10:30 PM
I do have an expansion tank...when the engine gets very hot it overflows....The system does draw the water back in again as it cools.

The rad cap is the one off the micra, I will have to check to see what the rating is compared to the subaru....

Is it possible that a single core rad with more air gap between the cores would work better than a three core with very little space for air flow?

I will check the thermostat and pump tommorow as well as callibrating the temp guage/sender...

Will post the results.


hover_southwest - n/a
5-Jun-06, 12:12 AM
just a thought or 2

running an osprey 5 MKII on a 1.8 citroen petrol engine. this engine has the diesel rad fitted due to bigger size and cooling effect of said rad, and works well.

also , do you have adequate ventilation UNDER the engine i.e. is there good air flow and a hole/vent for air to be sucked in low at the front and hence from below and over the whole engine creating a through-draft effect.

from the photo above it seems you have sealed the engine in its own little box. might be explaining this badly, so think of a car and the grill at the front along with the underside being totally exposed to passing air!

i do fully understand your wishes to keep out salt water, engine and electrical protection would best be kept to another thread than this one for now though http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

"I moved the radiator ages ago, no electric fan is going to help!" YOU WILL BE SURPRISED, an electric fan that close to the rad linked to the stat will work, as sugested by others !!!

oh, one last minor point, using your craft on a sandy beach, that air filter will more than likely get blocked pretty quick. looks like you have space to install one of the land-rover type oil-sump filters - no sand getts past one of these http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif


jar2 - n/a
5-Jun-06, 07:44 AM

As you know, I run two Subaru engined craft - both have radiators about twice the area of yours. The way your engine cover is designed will supply pre-heated air (from the engine) to the radiator - this may be making things worse.

Once you have checked all the obvious stuff that's been posted I would change to a larger radiator. Get a single core (about 30mm thick) radiator that has large fin gaps to stop it clogging up. Don't bother with an expansion tank - it's just extra weight and hose - get a far east car radiator same as you have. The original Subaru radiator pressure cap is 0.9bar - same as all the other cars I've just checked. They do vent a bit until all of the dissolved gas in the water has been released - you can never keep the radiator 100% full - although the level will stabilise eventually if you don't keep putting fresh water in

Look at the radiator as a 30kW heater - how big a fan-assisted domestic radiator would you need to do that?

Good luck.

Nick Long - n/a
5-Jun-06, 08:11 AM
Hi Dunc,

There is a way to tell whether it is a circulation problem or a radiator size / airflow problem.

Fit two temp guages (check them first), one on the flow from engine to rad and one on the return from the rad. Normally there is only a fitting for the first place, but clamping a sender to a metal pipe will work, the sender doesn't actually have to get wet.

If both measurements go hot, then the radiator isn't dumping the heat and you need a bigger rad or more air through it. If one goes hot and the other stays below, say, 60C, then you haven't got enough water flow through the rad.


Russ Pullen - n/a
5-Jun-06, 09:19 AM
also , do you have adequate ventilation UNDER the engine i.e. is there good air flow and a hole/vent for air to be sucked in low at the front and hence from below and over the whole engine creating a through-draft effect.

from the photo above it seems you have sealed the engine in its own little box. might be explaining this badly, so think of a car and the grill at the front along with the underside being totally exposed to passing air!

From my early experiences with car engined craft, i absolutely agree. As soon as i looked at the picture of your engine bay, i can see your problem. Think of the volume of cold air that that engine gets in the car, then look at your install. No wonder it gets hot. I'd duct some plenum air, double the size of your rad and do something with your engine cover to scoop air if i were you.

jar2 - n/a
5-Jun-06, 09:57 AM
I would have to disagree with the above - this is a liquid cooled engine. You can operate a liquid cooled engine in a sealed box if you want (plenty of examples of this around - marine outboards, etc..). If you have a look under a 4x4 and you will see a huge sump guard covering the bottom of the engine bay with none of the sump exposed to the airflow. You will also see that on virually every car the radiator is significantly heating the incoming air before it is passed across the engine - not a very efficient air cooling system!

Get the liquid cooling system sized and working properly and forget about trying to cool the engine directly.

Russ Pullen - n/a
5-Jun-06, 06:25 PM
In principle John, but most car engines don't get the nuts revved off them for hours at a time.

*Most* of the car engine installs i've seen have been 50k mile old engines, put in a box heavily restricting cold air from reaching the motor and/or rad, and then the poor thing is expected to sit there revving at 5000 rpm (so 100+ mph in the car) for hour after hour. No wonder they get hot and fail!

Back to the original poin tho - i've found oil coolers make a HUGE diffrerence to the running temp of engines, they're pretty cheap and very effective. may be worth trying too.

jar2 - n/a
5-Jun-06, 06:39 PM
You are correct, Russ, in most installations - but this is a "utility" Subaru engine that will be lucky to hit 4400rpm never mind 5000. A 50K mile Soob engine is just nicely run in http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif These engines were used in 4x4 pick ups that had to slog up mountains carrying god knows how much stuff and often towing a trailer - without overheating or breaking. They had a reputation for being unburstable. If you duplicate the original cooling system you will get the original reliability. Oil coolers (along with electric fans, etc) do work well but should be completeley unecessary for this particular engine installation. Fit a decent sized radiator and make sure it has good intake and exit airflow and it will be fine - I guarantee it!

Mart366 - n/a
5-Jun-06, 08:53 PM
The rad is plumbed correctly, but i think ive identifyed your problem dunc,

unfortunatly its what weve been telling you all along,

looking at you pic of your engine, i would guess that your engine used to have a direct drive fan fitted on the front of the water pump. Later J20 engines have the water pump driven by the cam belt, and a kenlowe type fan added to aid cooling, and contrary to belief they do kick in under normal use. The rad you have dosent have the same surface area as a scooby rad, so again you will never keep the beast cool. placing it at the back of the engine bay is fine in practice, but all you are doing is drawing warm air over an item you want to cool. You need to put cold air into the rad.

go to your local brown bros motor factors and buy a new rad, the scoob rad is very similar in size and thickness to a rover 216 gti rad (cost 56) new. And similarly theres no expansion cap on scooby rads! likewise the rover rad, the expansion bottle has the rad cap on.

i will check my sccoby manual to see if there is a correct filling procedure for coolant, some engines are known for airlocking big time.


srn4 - n/a
5-Jun-06, 10:12 PM
Ok, so I need a larger radiator...

How about I move the radiator and mount it above the upper pulley? Its going to restrict the air flow a huge amount unless I can find myself a small radiator which fits neatly into place...

I dont supose you have dimensions for the rover/subaru rad or an alternative that might work and fit inplace?

If I go for a large single core is that going to restrict the airflow too much?

Edited to say:

I guess the alternative is to get the biggest rad I can with twin fans and stick it back on the side of the cockpit wall and then add a big scoop on the engine cover....


jar2 - n/a
6-Jun-06, 07:39 AM

If you fit a bigger radiator it will stick up higher anyway - I would try it first - move it up if it still seems to overheat. A single core shouldn't restrict air flow to any significant degree otherwise it wouldn't work very well as a cooling device

The orginal Soob radiator is about 680mm wide by 450mm deep including header tanks and is copper core/brass header tank and weighs around 6.4Kg. You can get a selection of aluminium/plastic radiators from s c rap dealers that should weigh around 3Kg. The disadvantages of the ali/plastic radiators is that the steel crimp strips will corrode and the ali core will dissolve in salt water eventually. The advantages are that they are easy/cheap to replace and don't weigh much.

Don't fit electric fans - it's just extra weight and something else to go wrong! You've already got a fan (hint: that big plastic thing at the back of the craft http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif )

srn4 - n/a
6-Jun-06, 09:01 AM
Can I use any single core rad which is about 680mm wide by 450mm or does it have to be a scooby item?


jar2 - n/a
6-Jun-06, 09:51 AM

As long as the radiator has the same total surface area it should be OK - it doesn't matter what shape it is. In theory, it's simple to calculate the size of radiator using the engine output, flow rate and the thermal coefficient of the radiator - the problem is you don't know the coefficient of a particular radiator. My best advice would be to get a radiator from a car that has at least the same HP as the soob engine (based on the assumption that the same amount of fuel is being burnt therefore the same amount of heat needs to be dissipated).

At the peak efficiency of a Soob (or any other) engine of around 40% you need to get rid of around 120HP of heat (90kW http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif ) A petrol engine may be better described as a heater with the by product of some mechanical energy http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

srn4 - n/a
6-Jun-06, 11:14 AM
Ok.....Did a thermostat test...Took it out and suspended it in a pot of water on the stove...

It is suposed to open at 88 degrees...Im reconing it opened up at about 92. Once the water reached 100 degrees C the gap between the valve and the housing was only about 4mm....Is this normal?

It doesnt look like there is much space to allow water to flow, plus the water pressure will try and close the valve...

Does this sound like a normal valve? (I recon if it opened a bit more I could cool the engine a lot quicker!


jar2 - n/a
6-Jun-06, 11:55 AM
It should start to open (a small gap) at about 85 and be fully open by 90 or so. The gap sounds about right to me. If you are sure your thermometer is accurate then I would just go get another thermostat for all the price they are! Usually they either just fail to open at all or get stuck in the open position.

srn4 - n/a
6-Jun-06, 10:20 PM
I got a new thermostat....Its a pattern part....

The guy in the shop went though all his catalogues (as they do) and each one pointed to the part I now have....However it looks nothing like the old one....

Its the same physical size so it will go in the hole in the engine, but it looks completely different...the guy in the shop assures me its the right one.....

Should I trust it? I guess at the end of the day its still going to open and close http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

jar2 - n/a
7-Jun-06, 07:53 AM
Just stick it on the cooker too check it works if it will make you feel better http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif After market part designs do vary quite a lot so I wouldn't worry about what it looks like as long as it works.

fishy_fish - n/a
7-Jun-06, 07:05 PM
can you not find out how much heat the scuby rad can dissapaint in watts for example, with a certain airflow over it in say, meters per sec and a flow rate thru it in litres per sec for example at a certain pressure.

then get this data for a rad more available to you. and you sorted, if you talk to a rad supplier this sort of information might be available.

dont mess about, thinking oh this might do it. work out if it will then buy a new rad.

detailed car service manuals may have this type of info! know any mechanics?

why dont you get a scuba rad anyhow? or is it too expensive? using anything other than that you know will work before hand, is going to cost my more in the long run.

srn4 - n/a
7-Jun-06, 08:21 PM
The only reason why I didnt want a scooby rad was because they are a large physical size and the people I have spoken to recon they are inneffient....they reconed that something half the size with more cores would be better....Appaently not...



Did the same test with the new valve and it opens a good 15mm more than the old one at a slightly lower temp.... I wonder if this is the cause of the problem or if the rad is still too small....


jon_curtis - n/a
8-Jun-06, 05:39 PM
reconing apears to be the problem!

team black - n/a
8-Jun-06, 07:04 PM
The cooling would be more efficient if he rad were upright instead of making the air turn two corners (one on the way into the core and one on the way out).

Mart366 - n/a
8-Jun-06, 08:00 PM
Sorry Dunc, how do you justify that statement?

Subaru fit rads that work and match there engines, this means they dont overheat.

What is the concern you have??? A rad of sufficient size will not obstruct airflow, but will offer the best properties in terms of cooling and efficiency.

SOme other things thing to factor in, non cooling related. have you got sufficient clearance under the engine to carry out an oil change?? scoobys like oil to be changed every 6K or twice yearly, given that you will be running the engine flat out, you need a good regime.

And did you change the cambelt and tensioner on your engine??, scoobys have longer than normal belts and should be changed every 60k i believe. given your engine is of indeterminable age and milage, i would get the belt and tensioner checked changed as a priority


srn4 - n/a
8-Jun-06, 09:15 PM
Hi Mart.

I was just intreagued really as to how much of an effect a dodgy valve was going to make to the heat of the engine.....A new rad is in order though!

The engine has gear driven camshafts so there are no belts that want replacing (thankfully)....Whilst I was servicing the engine I checked the play in the gears and they are well within the recomended tollerences....The engine had only done 50K....

To change the oil the engine must be removed.....

By removing the engine all of the other components can be checked at the same time so its not such a bad thing..

Lets say that the engine wants an oil change every 6000Km and your average "flat out" speed will be 60Mph (100kmph) .. That means I need an oil change every 60 hours of opperating.....I am keeping a log of all hours on the engine so im hoping I can ensure the engine is looked after... 60 hours is quite a lot on a recreational cruising craft...But to be sure I do have long life oil in the engine!

(If my math is wrong then I wont be suprised http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif


jar2 - n/a
8-Jun-06, 09:54 PM

The oil change interval for the EA81 (from the Subaru manual) is 7500miles. That's for a pick up that's likely to have a pretty hard life. Assuming an average speed of 30mph that equates to 250 hours run time. This isn't a high performance engine so use cheap oil and change it once a year!

As your engine probably hasn't been run for a long while I would dump the new oil you've put in after a ten hours running - you'll be surprised how much muck the detergent has removed from the engine!

srn4 - n/a
9-Jun-06, 01:32 PM
I have been lent a pair of different size single core cross flow radiators which are close to the size of the subaru ones...

But....They dont have the same type of radiator cap on them with the pressure relief on them. http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

They have the usual in/out and a small nipple for the overflow, but how is it all connected up?

I do have an expansion tank with a small hose at the top and a larger one at the bottom..

Anyone have any idea how and If this can be connected to the scooby engine?



jar2 - n/a
9-Jun-06, 02:50 PM
You need to check your expansion tank is actually a pressurised tank (it should have a pressure relief cap on it (usually plastic). If it isn't then it's just an overflow tank (as fitted to rads that have pressure caps on them). If you fit the extra tank you need to make sure the high level mark on the tank is above the top of the radiator otherwise you will get air trapped in the system.

srn4 - n/a
9-Jun-06, 03:46 PM
Yes it does have a pressure relief cap on the top. Not sure what its rated at though.

Where do you plumb in the two hoses from the header tank?

I assume the smaller one at the top goes into the overflow on the radiator, but where does the larger one from the bottom of the tank usualy go?


jar2 - n/a
9-Jun-06, 04:00 PM
Without seeing the tank it's a bit hard to work out but....

I would say the lower outlet should connect to the radiator - it should be underwater all of the time. The upper outlet may be a drain from the pressure cap seat?? If not - just block it off if it opens into the air expansion area of the tank.

srn4 - n/a
10-Jun-06, 05:22 PM
Fitted the new rad with the pressurised header tank and sat it on the drive at 4000RPM for 15 mins....

Got up to 95 degrees quickly and then sat there without bouncing.

When I shut down to idle at 900Rpm the temp rises to about 98 degrees and sits there...as soon as I speed the engine up again the temp drops back down to about 95.

Considering how hot it is outside and the fact that I was stationary, (so no air flow) I consider this a great improvement!!!

I just hope it works out in the field http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Thanks for your help guys.


jar2 - n/a
10-Jun-06, 06:00 PM
Good to hear things are improving Dunc!

I've just gone and measured the temperature on one of the craft I have. At the point the thermostat opens (top hose starts to warm) - the temperature on the sender unit is 85.5C - exactly what it should be. After about 5 minutes of running at about 1200rpm the temperature is still 85C and the radiator is hot - again that is exactly what is supposed to happen.

If you are reading 95C with a brand new thermostat then (assuming the stat is OK) either the sender or gauge are faulty OR you still have a marginal cooling condition (the radiator is only just providing enough cooling effect to prevent the temperature rising further). I would suspect the latter as the temperature rises a bit more at tickover when the cooling effect of the fan reduces to almost nothing. You will find out when you start using the second choke and really burning fuel http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif Do you have the sender in the normal position on the engine (on the water intake on the inlet manifold)? The cylinder heads get to about 95-97C.

I assume you have the original Hitachi carb fitted? If you do then you may need to reduce the tickover to no more than 800rpm - if you are above this the main jet starts to work and the engine can run-on when switched off (learned the hard way of course http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif ). My engines will idle smoothly all the way down to 600rpm but the transition from the idle to main circuit can be a bit lumpy on one of them (one of the downsides of not having fuel injection!).

srn4 - n/a
10-Jun-06, 06:30 PM
I do still have the standard carb. I find that if I let it idle below 1000RPM its rather too lumpy and im worried it will stress soemthing so i keep it fastish so its smoother.

I have one of those aftermarket senders which sits in an ali block on the radiator hose between the thermostat and the top of the rad.

I thought the running temp was 95 degrees...my mistake!

I will see what can be done to get it to cool a little better....

I suspect some baffles to help suck the air into the radiator and perhaps some more antifreeze....

But I wonder if it will cure itself once I actualy allow it to move forwards(so more cool air flow) ?!?!

Atleast its a constant 95 rather than 120+ !!! http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif


Mart366 - n/a
10-Jun-06, 08:14 PM
The other thing with the genuine scooby rad, the header tank is integral to the rad, and makes things easier


Mart366 - n/a
10-Jun-06, 08:25 PM
Just to clarify something?? you say the engine has gear opeated cams??

are you sure? the ej20 is overhead cam, belt driven, the early engines, which would have probably come from a legacy would probably be pushrod engines, with tappets, these are not gear driven afaik, the only gear driven cam type engines i can recall at the mo are from honda, and ducati.

With regards to your oil change schedule, you are not going to be operating you engine in optimum conditions, sand and dust shorten your change window considerably, given you have an inherant cooling issue, your oil is taking some additional abuse, it thins under excess heat. This again shortens its working range and ability.

Re removing the engine when a change is required. How would you do that if you change window is mid cruise?? lugging a 200lb engine around at the best of times isnt easy.


jar2 - n/a
10-Jun-06, 08:52 PM

Dunc has an EA81 engine which is a pushrod engine with gear operated camshaft.

If he gets the radiator cooling sorted he won't have any problems with oil life. He could also remove the oil by sucking out of the dipstick hole (done this way in many garages).

srn4 - n/a
15-Jun-06, 06:45 PM
Got some good news....

First off I compared the onboard temp guage to two independant ones...the one onboard is acuraet to about plus/minus 3 degrees...

Added some baffles to the new radiator to help draw the air though it and it sits at a constant 86 degrees.... between 0 and 5000RPM.....If i take it above this the temp rapidly rises to about 90 but falls right back down if I drop the revs a bit...

Still not perfect, but is this good enough do you think?

With my old setup with the presurised rad cap the pipes would kinda go hard under the pressure a bit...with the header tank system instead the pipes dont get quite so firm...This sound ok?


jar2 - n/a
15-Jun-06, 07:13 PM

Sounds OK to me. You will get a little bit extra cooling when the craft is moving.

How do you manage to get 5000rpm out of an old EA81 http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif . The ones I have are loaded to peak at 4200 and 4400rpm. From memory, the EA81 hits peak power at 4800rpm. You shouldn't be running it anywhere near that for more than a few seconds or so, around 2800-3200rpm should be the normal cruise speed for best efficiency and the longest life!

The hardness of the hoses shouldn't be any different if the pressure caps are rated the same. A bit of a subjective measurement though!

srn4 - n/a
15-Jun-06, 09:07 PM

Are you sure your figures are correct?

If you are then I have a problem... http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif

Need to add some serious pitch to the fan!

Thank god I havnt run it fast for very long...

What kinda damage would I have done with over revving?

jar2 - n/a
15-Jun-06, 10:10 PM
I can't lay my hands on the data for the max rpm just now - it was on a web page someplace along with all the other Subaru engines. The only data I have is:

80HP at 4800rpm - 101 net foot pounds of torque at 2800 rpm

This isn't the correct site but it does have specs http://www.ultimatesubaru.net/80s/specs/general/1987brat.htm (www.ultimatesubaru.net/80s/specs/general/1987brat.html) l

I wouldn't worry, Dunc, these are robust engines - you aren't likely to have done any damage. All I'm saying is that, for best reliability and economy, you should try to use the engine as near as you can to the way it's used in a car (brief(ish) bursts of power to accelerate up to cruising speed followed by long periods cruising at medium power). You should have plenty of power with this engine on your craft so there should be no need to rev the nuts off it! It's also much more comfortable if you don't have a screaming engine behind you ear!

Don83000 - n/a
16-Jun-06, 02:13 AM
Duncan what pulley ratio are you running and what pitch do you have set and how many blades.

srn4 - n/a
16-Jun-06, 08:38 AM
at the moment I am happily cruising at 3000-4000RPM with no problem, but that extra boost might help....(if I fiddle with the pitch to increase the load will I be able to cruise at lower revs?)

What RPM do you recon I should limit the engine to then whilst it is stationary?

I am running 36/56 HTD pulleys with a multiwing 5Z/9/9

I think the pitch is somewhere around 45 degrees....


Don83000 - n/a
16-Jun-06, 11:12 AM
Duncan we ran the same ratio as you and same fan setup but was at almost 50deg we adjusted our blades on the trailer until we could get no more than 4200rpm then off the trailer this gave us 4800rpm we could maintain hover at 2200rpm and cruise nicely at 3000rpm and our water temp using a 3 core mini rad never exceeded 80*C and this was with no electric fan and no thermostat. As John said these are quite a bullet proof engine so the odd burst to 5K if you must wont hurt it but the one thing these engines do not like with a vengeance is overheating.

Ian Brooks - n/a
17-Jun-06, 07:35 PM

I might be wrong, appearances can be deceptive, but it didn't look like 45 degrees to me...


srn4 - n/a
17-Jun-06, 07:48 PM
You recon it was less?


Mart366 - n/a
17-Jun-06, 08:06 PM
Engine specs for your engine EA 81 are as follows

EA81 1800cc

Tickover 800+-50rpm

oil pressure 4bar@ 2500rpm

rad cap 0.8-1.0 bar

Thermostat opens 83.5-86.5


srn4 - n/a
17-Jun-06, 10:22 PM
Dont supose you have the max RPM figure do you Mart?

I recon the engine would tick over that low if I didnt have a whopping great fan slowing it down http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif (1000 is more realistic without the thing vibrating like a mad house)

All the other figures look about right appart from the rad cap...

How can I tell what pressure rating the header tank cap has? It doesnt say on it...just a Ford part number http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

Don83000 - n/a
17-Jun-06, 10:48 PM
80-82 1600 1595 68@4800 84@2800 EA-81 1600 cr 8.5

80-82 1800 1781 72@4800 92@2400 EA-81 1800 2wd cr 8.7

80-82 1800 1781 71@4200 92@2800 EA-81 1800 4wd cr 8.7

83-87 1600 1595 68@4800 84@2800 EA-81 1600 cr 9

83-84 1800 1781 73@4800 94@2400 EA-81 1800 cr 8.7

83-84 1800 1781 95@4200 123@2800 EA-81T 1800 turbo cr 7.7

85-87 1800 1781 73@4800 94@2400 EA-81 Brat, 85 2dr GL

85-89 1500 1595 69@4800 86@2400 EA-81 2dr

85-86 1800 1781 82@4800 101@2800 EA-82 4dr

85-86 1800 1781 94@5200 101@2800 EA-82 GL-10 MPFI & XT

85-86 1800 1781 111@4800 134@2800 EA-82T turbo

86-94 1800 1781 90@5600 101@2800 EA-82 SPFI

86-89 1800 1781 84@5200 101@3200 EA-82 SPFI 4dr 2wd

87-88 1800 1781 84@5200 101@3200 EA-82 carbed

srn4 - n/a
18-Jun-06, 05:05 PM
Just thought I would stick up some photos of the radiator baffle etc...

Its held together with cable ties for testing...so dont laugh! http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif



Pretty bad photos but you can see whats going on (I hope)


Ian Brooks - n/a
18-Jun-06, 08:58 PM
If I'd had to guess, I would have said 30 or 35 degrees... but I could be wrong, my eyes are out of cal!!!!


Sean Atterbury - n/a
20-Jun-06, 05:14 AM
Like a great man from a movie said "YOU NEED TO FIND YOURSELF A GIRL MATE"

Enough said.

http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif