Would an inboard squirt be possible?

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Davidrd
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Joined: Mon Aug 18, 2014 8:04 am
Location: Chicago IL

Would an inboard squirt be possible?

Post by Davidrd »

Hello everyone!

I'm planning to build a squirt over this winter and I have been contemplating the idea of making it an inboard using a small engine like a motorcycle engine. I imagine the engine would sit centered or a bit forward on the craft and the seats would be set at the rear. However I don't know all the finer details of inboard crafts, for instance, would the Squirts small size make getting the proper angle on the prop shaft too difficult? Has any one ever attempted this or even thought abut it? Ultimately I would just want to know if its possible or if I'm just crazy before I start the numerous hours of research. Any input or advice would be greatly appreciated!! :D

Thank you!
If its got a motor, chances are I like it!

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jenko
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Re: Would an inboard squirt be possible?

Post by jenko »


Davidrd
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Location: Chicago IL

Re: Would an inboard squirt be possible?

Post by Davidrd »

I must say if I had the money for an engine like that I'd give the old college try, but seeing as that I'm in college for one more year I don't have any money lol. But those are some awesome engines though :wink:
If its got a motor, chances are I like it!

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jenko
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Re: Would an inboard squirt be possible?

Post by jenko »

Vdrive and subaru engine would work, remember you have to keep the weight at the stern as thats how the boat was designed

fergal butler
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Re: Would an inboard squirt be possible?

Post by fergal butler »

If money is a bit tight stick with the outboard it will give you a lot more room in the boat and you could pick up a cheep one if you hunt around where with an inboard you will have to buy all the things that go with it like gearbox,prop shaft,prop,stuffing box,strut and rudder these are not cheep :shock: but with an outboard they come as one package :D

driver06
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Re: Would an inboard squirt be possible?

Post by driver06 »

Hello,
I know this is an old post, but have thought about this and wonder if the one of the smaller engine set ups from a jetski would do the job. Any comments anyone?
John.

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X23
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Re: Would an inboard squirt be possible?

Post by X23 »

Here is an answer to a really old post, but you might be still interested.

The real issues are HP and weight. A jet ski powerplant is a finely tuned system refined by years of competition, and it is natural to want to use one. In addition, users often tire of the toys or wreck them into something hard making used skis low cost, particularly in the fall of the year. A smashed hull often has a good engine, if it didn't sink in salt water after the crash.

So lets see how that would work. The target hull has a 10 HP recommended maximum, with no weight limit, see:
https://www.glen-l.com/phpBB2/viewtopic.php?t=25579

The good 'ole American hot rod spirit shows that you can often put a big engine in a craft designed for smaller. How big could you go & what would you give up? The starting point would be that 10 HP, a modern Mercury 4 stroke 9.9 is 84 lbs, and the 2 stroke engines from back when the hull was designed would weigh less. Bummer.

So taking a different approach, what has worked for others? I found posts where 35 HP outboards were used, and these are up to about 140 lbs, which sounds better, eh? I know that level of HP would really turn up the fun on that light a hull. You would have a few limitations, like limiting throttle at hard over helm angles so you don't have to learn how to rebuild a hydraulically locked engine from turning turtle, or how much fun it is to recover the craft from the bottom after that experiment.

It does have a throttle, and limiting the use of same can result in a lot of fun. Quite a few years ago I drove a friend's Aqua Lark with a 35 on it. The little Aqua Lark was designed for a 9.9, so the comparison is a good one. Here is one with what looks like a 20 or 25: https://www.youtube.com/watch?v=9dP1u0pIwo4

The Aqua Lark 35 was a rocket ship, and let us get some fine up close images of ducks taking off, along with the resulting boat wash & personal shower. So that is a possibility.

But wait, the 4 cylinder motorcycle derivative engines sound so much better, here is a Kawasaki 15F:
https://www.youtube.com/watch?v=FY6XSJ1S2rw
How about that? It has 160 HP, and that sound . . .

Well you would have a bit more weight at 189 lbs for the engine & pump, however it is not hanging off the transom. In fact the majority of the weight is farther forward. 957 lbs of thrust! With a hull weight of 120 lbs plus 200 for the powerplant then add 6 gallons fuel & you and you get about 495 lbs. Hey, that is about 0.52 lbs/lbs and the acceleration should flatten your eyeballs. It would be even more exciting than the 745 dry weight of the 2007 model 15F.

That 6 gallons would last about 45 minutes if you could average 100 HP, but what a ride.

It might even fit in the hull, here are some measurements I took of a 12F which is nearly identical packaging:
Engine is set forward of the pump with a shaft log to the “inner transom” so the pump is outside the hull
22 inches from front of engine to brace supporting the air filter
Underneath, 28 inches from aft edge of water intake to back of nozzle
Nozzle housing 11 wide, the retractable step is outside this but attached to the same casting
Engine itself is 17 inches long, 16 wide from extremes of both manifolds, intake on right side
5 feet from front of engine to back of nozzle

For another data point, there was an article about an antique 22 foot wooden boat with a single 15F, and the performance was said to be good. I cannot find that article now, post a link if you do. That would be a lot more weight of hull, so it could push a lot of boat.

Now as long as you are drooling, consider that a few more lbs would get you the Ultra 310 engine, which is the same externally with the addition of a mechanically driven supercharger. Yep, 310 HP with just a bit more weight. Out in Texas they say "Go big or go home!" However the 15F are more common and a lot less $$ for a used one.

It has been fun examining the alternatives, but seriously that 35 looks like about the practical limit. And it was fun among the ducks.

Jack

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