150hp Outboard Jet ?

[Juniata RiverRat]

Just recently bought a Snyder Jet Boat and I am considering a motor upgrade. The motor on it now is a 2004 Johnson four stroke 90 outboard that has been converted to a jet. I figured the motor is 115/90 so I am putting out 80.5 hp at the jet. Max horsepower rate for the boat is 150hp. With the rock proofing , full livewell , and my wife and kids the boat does roughly 22mph on gps. Anyone know what size outboard I would have to consider to get 150hp at the jet ? I used a formula off the net that tells me 200hp would give me 140hp at the jet. (hp X 0.7 = Jet hp) I just realized that buying a 200hp outboard would mean that the hp at the prop would be 200 , so I would be putting out over the max hp at the jet. I guess I need to know what outboard has 200hp at the motor instead of at the prop?

 

[Frank Acampora]

You have not so far been given an answer because you have too many variables. AND to add to that, you are over-thinking it.

All modern engines are rated horsepower at the prop. Thus, just to spit our numbers: If, for example a mercury 90 was fitted with a jet drive it would be rated as a 60. So 200 horsepower at the prop WILL give you 140 jet drive horsepower.

However, you must first find a jet drive that will fit the engine you are expecting to buy and then, you must match the impeller to horsepower. Then after all that, if stopped by the Gendarmes, you must convince them that your engine is no longer a 200.

 

[Chris1956]

Just cross out the 200 on the cowling and write 150 in crayon. That always works...

 

[1983 ercoa 21']

Jet drives are like lower units they will interchange from a few different years and hp !
I would be looking at the jet drive and finding out what other years and hp sizes it would work on it would save one alot of money!
you will probably find out that the jet drive will work on a larger motor with a simple change of the impeller