Max HP rating for a boat, how is it figured out?

[mudweiser]

I have an 1977 Ranger Fish/Ski 1750 thats rated for a 115. It currently has a 1977 Evinrude 115 on it thats due for replacement. I found a Merc Black Max 150 for a pretty good price. I'm wondering how they determine the max HP rating for a boat, and what happens if you over rate an boats recommended max HP? Thanks.

 

[Silvertip]

Re: Max HP rating for a boat, how is it figured out?

Oh boy -- here we go again. There are length, width, depth, and construction figures used in that calculation and what the rating plate on the boat says is gospel. That said, your boat can probably handle 150 HP with no problem. Oh goody you say! But don't dash off and buy that engine until you read on. You must understand it is illegal to overpower a boat. Now I've been confronted by a water patrol, Deputy, DNR person only twice in my nearly 7 decades of life so you will not likely be stopped either. However, if you are, the agent may indeed inspect for safety equipment and Yes-- overpowering. Even if you never see an agent as long as you own the boat, there is the risk of accident. Whether it's your fault or not, guess what the lawyers are going to do? Yup, they will go after all your stuff because you are negligent. Then of course there is the matter of your insurance agent. If he/she knows your boat is overpowered, they may drop you like a hot potato. If you don't tell them and you have a claim they may not admit you exist. Think this over carefully. Lawyers can read and there are probably lots of them looking in on this forum at any one time. [For all you know I may or may not be one of them.]

 

[BoatBuoy]

Re: Max HP rating for a boat, how is it figured out?

If you were a lawyer, you'd still be waxing eloquent in this thread.

 

[mudweiser]

Re: Max HP rating for a boat, how is it figured out?

OK, i understand and thanks for the response. Now, just for the sake of argument lets say my 77 Johnson 115 only really has 100HP which is most likely what the prop rating was when it was new, if even that. Now i replace that with a nice new Merc or whatever mfg 115 which is rated at 115 Prop shaft. Did i overrate the boat, NO but if i put on a 1970'ish 120 it's considered overrating. I completely understand your response i just thought i would trow this out there.

Just an idea, will the power head from a johnnyrude 140 fit on my 115 midsection, this way i could keep the model number plate....... "Just Kiddin" Thanks to all who responded.

 

[gcboat]

Re: Max HP rating for a boat, how is it figured out?

Well, here's the regs if you're interested: http://www.uscgboating.org/safety/boatbuilder/part1/reg33_183_4a.htm

 

[Bob_VT]

Re: Max HP rating for a boat, how is it figured out?

There are boats that now have ratings for weight of the outboard and the max HP.

Don't question it..... you will just go nuts. Stay with the 115 max and a newer one will be more powerful than an old worn out one.

 

[deejaycee_2000]

Re: Max HP rating for a boat, how is it figured out?

a 150 black max will do nicely ......

 

[gotboostedvr6]

Re: Max HP rating for a boat, how is it figured out?

Install the newest 140 crossflow powerhead you can. You will see 40 or 50 more hp at the prop and 15 mph or more.