Naive HP rating question...

[Spinkick]

How is the horsepower limitation determined for a boat. Example, my 18.5' Nitro FS is rated for 150HP max. What prevents me from replacing it with something a little bigger? Say 175HP or 200HP for example...

I checked the dry weights on NADA to see how much of a factor weight would be and didn't see much of a difference. Is it control at the top end or something else? Would a governing agency get really mad at me? :redface:

Thanks for the input. Hope all had a good holiday.

 

[wildmaninal]

Re: Naive HP rating question...

Is it control at the top end or something else?

There has been alot of questions on overpowering a boat lately. The control at top end could be dangerous. I've heard of a couple of cases where somebody installed a bigger motor then what was recommended for their boat and they could not go above half throttle because the boat was to hard to handle.

There is a calculation that can be done to find out the max hp rating for your boat, might want to do a search on the subject.

I look at it like this....My boat is rated for an 85hp, guess what I got on the back of it.............An 85hp. It gets me to where I need to go, I'm in no big rush to get there, the boat is plenty fast enough for me.

Tashasdaddy has a posting about this subject, concerning the coast gaurd rules, he may actually be by here with it.

 

[Frank Acampora]

Re: Naive HP rating question...

You will notice that there are no horsepower regulations for racing hulls other than class size. Of course, racing rules set hull parameters but generally a racing hull has a much higher horsepower to size and weight than a pleasure boat.

Most boaters are not racers and many of them only know the fundamentals of boat handling. Goast guard regulations take into account the volume of the hull with consideration to freeboard, transom height, and hull type (flat bottom, deep vee, etc.). This ensures that the combo of hull and engine will be safe for the average boater under most normal circumstances. Of course, we all know of at least one person who should not be trusted with a dink and 1 1/2 HP. I know one person to whom oars would be too much power.

If you know what you are doing, you can safely overpower almost any hull BUT This doesn't absolve you from negligence if you cause or are involved in an accident.

Yeah, your Nitro could probably handle 200 Hp but your insurance company would not like it and you would not see that much of a increase in top speed.
Local gendarmes could ticket you and conceivably confiscate the boat. Coast guard could cite you for being manifestly unsafe and prevent you from using the boat--that is, have you towed to shore--expensive.

 

[tashasdaddy]

Re: Naive HP rating question...

The United States Coast Guard has an opinion on this frequently asked question, and their answer from their website is reproduced below:
Can I use a bigger motor on my boat than what it's rated for?
It is not a violation of Coast Guard regulations to install or use an engine larger than specified on the capacity label, but there may be state regulations prohibiting it, and restrictions from your own insurance company regarding this.
There are no Coast Guard regulations against exceeding the safe loading capacity, however, there may be State regulations or restrictions from your insurance company which prohibit this. There is a Coast Guard regulation that gives Coast Guard Boarding Officers the power to terminate the use of a boat (send it back to shore) if, in the judgment of the Boarding Officer, the boat is overloaded. There is no fine for this, unless the operator refuses the Boarding Officer's order. We certainly hope that you will abide by the rating, as overloading may lead to capsizing or swamping of the boat.
NOTE: The Coast Guard Capacity Information label is required only on monohull boats less than 20' in length. The label is not required on multi-hull boats, pontoon boats (catamarans), or on any sailboats, canoes, kayaks, or inflatable boats, regardless of length.
As the Coast Guard mentions, local regulations may apply. For example, in the state of Ohio one should be guided by this regulation:
Capacity Plates
(ORC 1547.39 & ORC 1547-40)
No person shall operate or permit operation of a watercraft in excess of any of the stated limits on the capacity plate. When no capacity plate exists, no person shall operate or permit operation of a watercraft if a reasonably prudent person would believe the total load aboard or the total horsepower of any motor or engine presents a risk of physical harm to persons or property

 

[Spinkick]

Re: Naive HP rating question...

You guys are quick on the responses! That's great.

I wasn't planning on overpowering, was really just curious.

The Skeeter SL210 maxes out at 225HP. But the straight bass rigs of the same size were 250-300. Just got me curious. Glad I'm not a cat.

THanks again guys.