Need Help to determine power source for 15' Gentleman's Racer

[Tony Carvalho]

I recently purchased a 15' Rascal - designed by Ken Bassett. It came with a 2003 - 40hp Johnson outboard motor, however, I want to run it with either a 1971 Mercury 1350 (135hp) that I own or a jet drive system like the Sport jet 90 (which I also own) or possibly a Sport jet 240. I like the clean inboard design of the Sport Jet systems, but I understand that jet systems sacrifice top end speed. There is a guy out west near Seattle Washington (YouTube handle: Peter1708) with the same Rascal boat using a Mercury 1400 (140hp) and is reaching low 70 mph. I don't know if I want to go that fast, but I would like to at least run in the high 50's to low 60's. What do you guys recommend to power this boat? Thanks.

Here is a picture of Peter1708 Rascal and a video link to his 70+ mph run:
(He has a bunch of videos)
70mph Mercury Inline 6 Tower of Power Home Built Wood Boat (Rascal)

 

[bajansailor]

Welcome to the Forum Tony.
I am just wondering - you say that you would like to run this boat in the 'high 50's to lower 60's'.
Have you ever actually travelled in a 15' boat at this speed?
Do you want to get from A to B at high speed, or do you just want to simply zoom around?
How fast does she run with the existing 40 hp outboard motor? Have you tested her out with this yet?

 

[montero]

70hp two stroke is probably enough to reach 60mph . Hull/driver weight and type of propeller makes basic differences.

 

[BlueBell]

Seems kinda obvious to me the 135 would be the choice given the options, no?

But are you sure the boat ( and you ) are up to it?

 

[BlueBell]

...also, Tony, what was the top speed with the supplied 40HP Johnson?

 

[peter1708]

Tony,

Congratulations on your new Rascal! She'll exceed expectations with any engine.

If you do go with higher horsepower with speeds over 60mph, I'd strongly suggest hydraulic steering, or the old Mercury Ride Guide two cable system (if you can find one). These options will take out any play in the steering and engine vibration. Or, if you go with the single cable system, put in some solid motor mounts, or at least brand new rubber ones.

If you have any questions, please feel free to contact me at my email: peter1708@hotmail.com

Best,

Pete

 

[Tony Carvalho]

Thanks for everyone's thoughts and comments. After a long Pros vs. Cons lists of all the possible powertrains available, I decided to go with a 2009 Kawasaki STX-15F engine and a Yamaha 1200 jet drive. The engine is 1498cc, 4 cylinder, 4 valve per cylinder, fuel injected, 4 stroke engine with 160 hp @ 7500 rpm. On the advice of several Kawasaki jet ski experts... I'm using a 155mm jet drive pump from a Yamaha 1200 instead of the standard Kawasaki 148mm. I'm doing this for 2 reasons... It's a complete aluminum jet drive that includes the intake and it has trim control. I picked up 2 Kawasaki STX jet skis off Facebook marketplace (2009 & 2008) so that I would have all parts needed to build one good running engine. I have removed the engine from the 2009 ski and will be removing the engine from the 2008 ski soon. What I like about this engine is that it has been in production for 22 years; there are a lot of aftermarket parts available; and if I really lose my mind... I can drop in another version of this engine that is the exact same engine with forged pistons and forged connecting rods with a roots blower and intercooler producing 310hp!
Here are some pictures...

 

[montero]

Thanks for sharing information . Good to hear.