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View Full Version : Jet Horsepower Ratings

Jet Newbie
09-13-2010, 07:24 AM
It appears that most manufacturers derate their products 25% when using a jet pump but
none appear to label the outboard with the lower rating.

What is the legal (Coast Guard and Insurance) rating of a Jet Outboard?

Can this rating be changed by detuning (throttle limiter or smaller sleeve/impeller)?

Thanks for any info!

Steve Herschbach
09-13-2010, 06:36 PM
I will get back to you tomorrow on that unless Nick beats me to it!

Are you running the Kenai River?

Steve Herschbach
09-14-2010, 02:54 PM

Well, actually all factory produced outboard jets at this time are rated at the nozzle and the cowlings are labeled to match. If a dealer adds a jet to an outboard, the decal also usually is changed, though in Alaska that might not always be the case. You may be referring to an instance perhaps where somebody is adding an aftermarket jet to an outboard themselves?

There are all sorts of ways of changing output horsepower but for it to be acceptable to USCG and insurance companies it usually needs to be done by a dealer, and usually only then if a factory kit is available to do the job. We used to install factory throttle delimiters on 50HP outboards to detune them to 35HP back when the Kenai River had a 35HP restriction. The kit included a new decal. Nobody made a 35HP so you had to detune larger motors or use a 30HP. But they since have raised the limt to 50HP so there is no need to do that any longer.

If you are looking at a hull max horsepower limit keep in mind it is about more than just horsepower. Lets say you have a Jon boat rated at 35HP. In theory you can put a jet unit on it that is rated at 35HP at the nozzle and be just fine with the Coast Guard and the insurance company. But you are still hanging a big heavy motor on the back of a lightweight boat, especially if you are talking about a 4-stroke motor. Proper weight and balance are an issue so do not let common sense be ignored just because you can get the requirements to match up on paper.