View Full Version : Scat Intruder 503

Jens Lange - n/a
22-Jul-08, 05:17 PM
I have just joined your nice forum. In Denmark we don't have such a forum, as hovercrafts are very rare here.

Many of you seem to have a good time with your Hovercrafts.

A few month ago I bought a Scat Intruder with a Rotax 503.

To be honest, I don't know much about what I have bought http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

But I have tested it once on water, which you can se here:

http://www.surferne.dk/forum/forum_posts.asp?TID=358 (www.surferne.dk/forum/forum_posts.asp?TID=358)

Can anyone tell me a litle about this Scat Intruder 503, compared to other similar hovercrafts?

What speed can I expect?

Can it float with stoped engine?

My guess is that it performs well, but other crafts do (much?)better.

From Jens.


Keith Oakley - n/a
24-Jul-08, 10:53 AM
Hi Jens

Although the Scat was designed in England it was built in the US and most of the fleet are over there, which is probably why no ones answered your post. I've only seen 2 Scats in the UK both with the lower powered 447 engine so I can't speak authoritively but I would expect your craft to perform as well as many of the other craft in Formula 503 (Formula 50 in Europe), but yes there are faster craft. It should do 40-50 mph over calm water or well cut grass. It should float with the engine off but there's always the possibility of battle damage causing an unseen hole in the hull so better to test in shallow water first.

Why not come to the World Championships in Sweden in August - as a novice I don't think you'd be allowed to race but at least you'd see what you can do. There are active clubs based in Bremen and Netherlands you could join.


StuDewis - n/a
24-Jul-08, 03:44 PM

I have a Scat II HP which has a Cuyuna 430cc engine, it is a little underpowered and probably more suited to cruising than racing, however it is robust and very forgiving when your a learner like me. It floats really well, which I found out at Claydon race meeting when it stopped on the water a few times.

I would think with a 503 engine it will be a little more powerfull and a great craft to learn in.

Cheers Stu.

kach22i - n/a
25-Jul-08, 09:43 AM
I have a 1989 Scat II HP with Cuyuna ULII02 (35 HP) and live in the USA. The Rotax 503 (50 or 55 HP) has the power to overcome many of this crafts short comings.

Things you should know about your craft:

1. You will want to wear ear protection, eye goggles, knee pads, life vest and bike gloves with palm padding in them. Adding seat padding is a good idea too. Remember everything gets wet and muddy including you and your passenger.

2. That constant water spray coming over the bow is a normal thing. If that annoying spray ever stops, move your weight back and give it a little more throttle as you are about to "plow-in".

3. Going even a little sideways on land can be dangerous and painful. The landing skid may make ground contact and throw you out of the craft. That life vest will help cushion your fall on land or ice. Come to think of it a helmet is required on ice, hovercraft love flat ice, but beware of tail winds. I have never been thrown out of my craft, but know first hand that the dash is harder than my flesh and bones.

4. Tail winds are your enemy (and so is weight). Tail winds force the nose down, this can lead to plow-in. Plow in is a sudden and often unwanted deceleration, look the term up.

5. It's much easier to start on land, getting up to speed and up on cushion from a dead stop on water requires some patience and understanding of getting over the hump (full power - don't let up).

6. My Scat has a lighter engine, but sits tail heavy in the water. Aftermarket products such as extra foam flotation are popular. Waves and wake from curious passing boats may come over the sides as it sits low in the water. Starting with a pull start on water is very tricky as you put all your weight to one side. Electric start has it's advantages.

Jens Lange - n/a
25-Jul-08, 12:46 PM
Ohh thank you.. that make all sence.

I wondered a few times why the craft was so slow - of course it just has to have full power in order to 'get out' of the water as any other boat.

My conclusion was, that it was due to water in the back row of shirts. They are not open, but sewwed together - is that normal?

Allthough I have been driving racing karts for not so many years, the Scat 503 is for crusing. But always nice to have some extra power. With 80% throtle it stil had a very fine speed.

Even if it only will do 40-50 km/h, and not mph, sounds exciting to me.

As far as I have been able to see from pictures, it looks like the Scat has a litle fan diameter - thats why I expected it to perform less well, but I can understand that it is not so bad.

RIGHT - it is noisy! After a few minutes my ears was in pain, and I had to find someting to put in the ears http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

I think I will add an extra muffer and damping in the intake.

I also did that on my homemade motorunit for my paraglider, and it's working perfect without any noteble powerloss.

I also understand that you can be throun out of the craft.

I am not really prepared for such things, so I better look a bit into the safety regarding this sport http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

jon_curtis - n/a
25-Jul-08, 03:03 PM
you can get rotax standard intake silencers and an aftermuffler, of which do have a very small impact on performance, not much tho, around 1.5 hp if i remember correctly! the aftermuffler effectively makes the zorst several inches longer and therefore will bring your torque band down a little, which for what your doing would be ideal!

also if you fit the rotax intake silencer, you need to change the main jet size.

you may very well know this sort of thing, but you can melt a piston with the wrong setup!

have fun


kach22i - n/a
25-Jul-08, 03:56 PM
back row of shirts. They are not open, but sewn together - is that normal?

Yes normal, they are sometimes called cones, closed finger or chip bag style.

I think I will add an extra muffer and damping in the intake.

I also did that on my homemade motorunit for my paraglider, and it's working perfect without any noteble powerloss.

I tried a spark arrestor dirk bike series of muffling plates on the end of my exhaust once. It did rob me of power, but the craft was still noisy at full throttle. I took it off, it was not good.

Just off the top of my head I'd say 2/3rds of the noise is from the fan, because it spins so fast. The other 1/3 is from the engine and exhaust. The higher frequencies which seem to offend people are coming from the fan (small diameter and high rpm), not the engine.

I have made my Scat much more quiet, it's not an easy task. Enjoy your craft for a few years before trying to do anything which cannot easily be reversed.

EDIT: Thread on NOISE

http://hovercraft.org.uk/FUDforum2/index.php?t=msg&th=12 (http://hovercraft.org.uk/FUDforum2/index.php?t=msg&th=1220&start=0&S=cb74fbdd8650701bc4e9084839a82bae) 20&start=0&S=cb74fbdd8650701bc4e9084839a82bae

Bob Beech - n/a
28-Jul-08, 10:32 PM
I note the comments about it being easy to be thrown out of the craft if it grounds out going sideways. I also have a Scat with a Cuyuna 35 Hp engine and when I first got it found this out.

However, the Scat is so easy to drive that I wanted it to be available and safe for anyone to use as a trainer and for giving rides so had to overcome this problem which is caused by the runners being very close to the join of the base of the hull with the planing surface. By filling the gap between the runners and the join with a triangular wood batten just stuck on with Sikoflex the sharp edges of the runners are protected and there is now a small smooth surface for the craft to slide on if it grounds out.

Following fitting these battens the craft has been transformed and I have lost count of the number of inexperienced drivers that have driven it without problem. Nevertheless, shutting the throttle when travelling sideways at speed is still not advised as it would be for any craft.

Jens Lange - n/a
29-Jul-08, 05:42 PM
Absoluttely great information you all give here http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Some off it have crossed my mind, but it's great that you point out the important things.

Glad to here the the Scat can be used with less power, good beginner craft etc.. - keeps me optimistic.

I don't intend to make a lot of drastic changes to it, but wood besides the runners, intake dampers etc. should be done - soon.

FANTASTIC pictures and videos from your races! I have started to link to your forum - maybe we soon will have something similar in DK http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

kach22i - n/a
6-Aug-08, 09:14 PM
By filling the gap between the runners and the join with a triangular wood batten just stuck on with Sikoflex ....

My original runners are off, but I developed a similar detail. It does work, it's wider to serve as a jacking point as I was putting too many holes in the ABS plastic hull.