An odd idea-is it possible?

Nos4r2 · 17 July 2006, 02:25

I've been daydreaming recently about the idea of fitting a small (JS440 or 550) jetski motor to a SIB.

Would it be feasable to put the jet outside the transom and the engine inside both bolted to the transom in the same way that Castoldi do so as not to put any weight on the floor and have a solid driveshaft?

The idea is to make something that'll fold down small enough to store easily, be usable in very shallow water and that'd go quite well. It would make an ideal rescue boat too-no prop to get caught in. It'd be rather a lot of fun too at a guess.

Any comments?

If anyone does it then the idea is (c)Me!

Pete7 · 17 July 2006, 08:31

Sure I have seen somewhere the jet and engine plus running surface from a jetski being cut out and then glassed into another hull. Leeway has a small 2.5m mould which he could make you a hull.

Pete

ian parkes · 17 July 2006, 19:23

isn't that what the small seadoo rib is . Don't know much about it but read all about it recently when looking for a rib .

As for the shallow water use , I often launch at Looe on a tidal estuary where lots of jet skiers seems to launch, they all say the jet hates the mud and silt and one comented to me that if he opened the throttle in shallow water the thing would just suck itself to the bottom . they also clog with weed badly .

Just passing on what I hear , I know nothing about the things myself.

Nos4r2 · 18 July 2006, 00:20

Erm.... I said SIB not RIB. No part of the jetski hull or any fibreglass would be in contact with the water.

Powerboats · 18 July 2006, 18:08

Would be difficult to do with a SIB because you will need to mount the water intake in the floor somewhere presumably?

Nos4r2 · 18 July 2006, 19:45

No-Castoldi make jet drives where the entire jet unit is outside the boat-including the water pickup and the propshaft goes through the transom via a rubber boot.

I'm thinking the same kind of thing with a drive unit from a jetski-build a cage to hold the engine and another to hold the jet on the rear of the transom to balance itself out. Would the suction of the intake be a problem in doing that?

jyasaki · 18 July 2006, 19:48

Why not just get an outboard jet and mount it on the transom?

Yamaha makes one, I believe (perhaps several.)

That is, unless you happen to have the parts lying around...

jky

Nasher · 18 July 2006, 20:48

Quote:

Originally Posted by jyasaki

Why not just get an outboard jet and mount it on the transom?

Yamaha makes one, I believe (perhaps several.)

That is, unless you happen to have the parts lying around...

jky

Because Matt is like me, and gets far more pleasure from making something, and if possible doing it differently to anybody else.
And if somebody says it can't be done - its just got to be tried.

Oh, and spending money is definatly not on.

Nasher.

Searider · 18 July 2006, 20:56

Sure I saw it done on scrapheap challenge last winter - although they used the roof of a transit as their hull!

Nos4r2 · 18 July 2006, 22:16

Quote:

Originally Posted by Nasher

Because Matt is like me, and gets far more pleasure from making something, and if possible doing it differently to anybody else.
And if somebody says it can't be done - its just got to be tried.

Oh, and spending money is definatly not on.

Nasher.

Summed me up in 4 lines!

Biggles · 18 July 2006, 22:20

Matt,

My friend was big in to Jetskis. He also commented on how bad they were at sucking up bags, stones and general crap. He said they needed much more clear water than a RIB.

Nos4r2 · 18 July 2006, 22:22

Thanks Nick,

I guess it's a bit of a no-no then.

Biggles · 18 July 2006, 22:29

Matt,

Don't be put off. Surely it just needs some sort of a filter.

The Western Airforces suffer terribly from Foreign Object damage (FOD), that is crap sucked in to the jet engine intakes which knackers the engines.

The Soviet alligned Airforces get round this by having adjustable grills which they use whilst on the ground.

Obviously there is a reason why the West doesn't use that sytem. But whos to say who is right.

Biggles · 18 July 2006, 22:34

I think I also read in an old issue of RIB International about a RIB in New Zealand that worked the inland waterways that was fitted with some sort of outboard jet that had a large grill on the intake. They said they used it in shallow water and it was safer for people in the water.

Nos4r2 · 18 July 2006, 22:46

Yeah, I guess that'd work.

This IS only one of those daydreams at the moment though-subject to a SIB and a jetski coming along for next to nothing.

Bear in mind I was wondering about the idea of fitting a jet engine to a rib as well when my mate came home with 3 surplus engines

Dirk Diggler · 05 August 2006, 08:48

I think you'll find that these people have beaten you to it!

http://www.swordmarine.com/

Jonny Fuller · 05 August 2006, 08:57

I now a fella in Jersey who has a couple of the jet units described here laying around in his garage.

They're a centrifugal pump that mounts to the transom, with a scoop poking it's nose out below the running surface.
Just has a shaft going through transom, nothing else. quite small, but look horribly in-efficient.

Nos4r2 · 05 August 2006, 21:19

The castoldi jet or the ones pictured above?