Powering a Boat Above Maximum Horsepower Rating

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Powering a Boat Above Maximum Horsepower Rating

Postby mgerson » Wed Jul 25, 2018 9:40 pm

I may buy a 1973 16 MONTAUK I which was recently re-powered with E-TEC 115-HP. The Montauk maximum horsepower rating was 100-HP.

Are there any legal concerns with having over 100-HP?

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Re: 1973 Montauk 1 Power

Postby Jefecinco » Thu Jul 26, 2018 9:51 am

I can't imagine any legal problems. What do they say about free legal advice? It's worth about what you pay for it.

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Re: 1973 Montauk 1 Power

Postby msirof2001 » Thu Jul 26, 2018 11:14 am

Back in the day we put a Chevy 327 into a Chevrolet Vega wagon. Got pulled over. The cop was doing the same and wanted to check it out and ask how we did certain things to support all of the torque. No legal problems as long as it met smog requirements.
Current: 2017 Everglades 295cc, Previous1: 1995 Boston Whaler Outrage 21, Previous2: 1974 Sevylor Caravelle 3-man liferaft.

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Re: 1973 Montauk 1 Power

Postby Bhungerford » Thu Jul 26, 2018 11:42 am

I advise against overpowering. I have a 1977 SPORT with a 100-HP Yamaha. I am unsure I’d be comfortable with the extra 15-HP.

I suggest to not go over the horsepower limit. I estimate that boat will do close to 55-MPH. I am unsure I want to do that in an older hull.

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Re: Powering above Hull rating

Postby jimh » Sun Jul 29, 2018 5:56 am

mgerson wrote:Are there any legal problems with having over 100-HP?

The FAQ has a well-researched answer to your question.


If you are not comfortable with the 45-year-old boat having an engine that exceeds the original horsepower rating and probably also weighs substantially more than a 90-HP modern engine, then look for another boat. There are many used Montauk boats available.

In c.1973 the OMC 90-HP engine was probably a rather heavy V4 configuration, so the weight of a current Evinrude E-TEC V4 is probably not too much more. You might compare the weights to get a better idea of how much transom weight the MONTAUK hull could handle.

No matter the engine weight or power, the integrity of the transom on a 45-year-old hull is a primary concern on any boat considered for purchase.

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Re: Powering a Boat Above Maximum Horsepower Rating

Postby thill » Thu Jan 03, 2019 1:51 am

I had a 1987 Montauk 17 with a 2001 Johnson 90-HP on the back, and it was scary-fast. Not so much the top speed, but the acceleration from a standing start was ridiculous. You had to feather the throttle to keep from throwing people out of the boat. I imagine that an E-TEC 115 would be similar.

I ended up swapping the 90-HP for a 70-HP, and that was a great combination. Great acceleration from a standing start and great fuel economy--it was a perfect match. But that's the old man talking. That kind of power was intoxicating.

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Re: Powering a Boat Above Maximum Horsepower Rating

Postby Phil T » Thu Jan 03, 2019 11:36 am

While there are no laws against exceeding the capacity plate, you should verify your insurance carrier will concern coverage. There are many insurance companies, so don't fret if your current insurer declines.

Take a look at this archived thread: http://continuouswave.com/ubb/Forum4/HTML/006494.html

Expect WOT to be between 46 to 48-MPH, engine mounted three-holes-up with a 13-7/8" x 19” BRP Viper.
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Re: Powering a Boat Above Maximum Horsepower Rating

Postby dtmackey » Thu Jan 03, 2019 12:57 pm

Several outboard boats I’ve owned over the years have been overpowered by 10-40% and never a problem. Just because it’s there doesn’t mean you need to use it, unless you need it for a heavy load or towing skiers.

Overpowered boats owned:

2 - 13’ Whalers with 50hp, rated for 40 (past)
1 - 17’ Montauk with 110hp, rated for 100 (past)
1 - 9.5’ AB RIB with 25hp, rated for 15 (current)
1 - 21 Mako with 250hp, rated for 225 (current)

Many of these I just applied decals of the lower hp model so as not to attract attention. Insurance has never been a problem.


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Re: Powering a Boat Above Maximum Horsepower Rating

Postby Todd » Thu Jan 03, 2019 2:24 pm

Happy New Year. Just another thought:

In addition to the potential of your boat insurance being voided (or not based on your policy) and likely any warranty left on the engine, I would add you could be held liable for personal injury knowingly overpowering a watercraft. Even with you were trying to manage the power appropriately and not operating the recklessly, should there be an accident (your fault, their fault, nobody's fault) an investigator seeing that engine and a smart lawyer representing any injured party would have good leverage to sue you.