Boat max HP rating question

[LoonASea]

If a boat is rated at 150 HP and has a 150 on the transom as the main engine can a person add a 9.9 kicker which in my mind exceeds the max HP of the boat but I have been wrong so many times this year already whats one more time ,,,And who designates what the max HP is Mfgr or Coast Guard

LAS

[leechlake]

You can add the kicker. It is an interesting point though since, especially in salt water, some boats run dual 150's for example. In that case the boat must be rated for 300 minimum.

Don't know about the Coast Guard vs Mfg. I'd bet it's the Coast Guard but the Mfg knows how they do it and builds the boat accordingly.

[leech~~]

I think it is just the rating for the main motor and they don't add up total HP. There are tons of boats out there with a Max motor on them and a smaller kicker on the side. I'm sure the MFG's have some kind of formula given to them on how to rate the Max HP by the given transom materials buildup of it and the weight of the boat.

Just found this but you would have to look up all the code sections.

CHAPTER I--COAST GUARD, DEPARTMENT OF TRANSPORTATION (CONTINUED)

PART 183--BOATS AND ASSOCIATED EQUIPMENT--Table of Contents

Subpart D--Safe Powering

Sec. 183.53 Horsepower capacity.

The maximum horsepower capacity marked on a boat must not exceed the

horsepower capacity determined by the computation method discussed in

paragraph (a) of this section, or for certain qualifying boats, the

performance test method discussed in paragraph ( of this section.

(a) The maximum horsepower capacity must be computed as follows:

[[Page 755]]

(1) Compute a factor by multiplying the boat length in feet by the

maximum transom width in feet excluding handles and other similar

fittings, attachments, and extensions. If the boat does not have a full

transom, the transom width is the broadest beam in the aftermost quarter

length of the boat.

(2) Locate horsepower capacity corresponding to the factor in Table

183.53.

(3) For a boat with a factor over 52.5, if the horsepower capacity

calculated in Table 183.53 is not an exact multiple of 5, it may be

raised to the next exact multiple of 5.

(4) For flat bottom hard chine boats with a factor of 52 or less,

the horsepower capacity must be reduced by one horsepower capacity

increment in Table 183.53.

[SkunkedAgain]

Your best bet may be to clarify with your boat insurance company. I doubt this would be a trigger for denying a claim, but you'd hate to find out AFTER an accident that they claim your boat was overpowered and therefore unsuitable for safe use. A quick phone call to you agent will ensure you are in the clear

[Whoaru99]

Surely the policies wouldn't be so silly that the HP rating of the boat relates to anything other than the combination of engines you're using for primary propulsion?

150 + 150 = 300 because the pair of 150s is the primary propulsion. 150 + 9.9 = 150 because only the 150 is the primary propulsion. This is my opinion, not stating it as fact.

[leech~~]

Surely the policies wouldn't be so silly that the HP rating of the boat relates to anything other than the combination of engines you're using for primary propulsion?

150 + 150 = 300 because the pair of 150s is the primary propulsion. 150 + 9.9 = 150 because only the 150 is the primary propulsion. This is my opinion, not stating it as fact.

That was my point above as well. They only count the main eng.

[pinkfloyd4ever]

my insurance agent said it has more to do with weight of the motor than propulsion. For example, just hypothetically, "a friend" of mine has a boat that is rated for 40HP but put a 50HP on it. The boat owners manual says that the max transom weight of the motor shall not exceed 265 lbs. The 50HP motor he put on his boat weighs 239 pounds. My "friend" pays like $2 more a month for having a higher rated motor on it.

But I, I mean, he knows there could be tickets or such for exceeding HP capacity