max HP question

[ClownColor]

What does the max HP mean on a boat? I guess I always thought it had to do with weight but then why wouldn't they list that instead? I guess my questions stems from wanting to put a outboard on a canoe. label states max 4 hp. So I can place a 4 stroke 4 hp on it? would it matter if the boat was made pre or post 4 strokes? Do you think they have a safety ration (a pressure vessel may be rate for 100 psi but is tested to pass at 150 psi).

Just curious is anyone is in the business and would know. I just want to put a 4 stroke 4 hp on a canoe with max hp rating of 4 hp....but but was made in the '80's.

[RebelSS]

Four stroke or two stroke has nothing to do with it. Max HP is the largest allowable HP engine you can put on a boat for it's size, weight, and carrying capacity. So, the biggest engine you can put on the canoe cannot exceed engines listed as 4 HP.

[JohnMickish]

The weight also comes into play as it is counted in the weight capacity of "Max weight, persons and equipment"

[delcecchi]

The USCG has a formula that they use to calculate it. If the manufacturer rates the boat at less maximum hp than the value the formula gives, no testing is required. If they want a higher rating then there is a testing program. The manufacturer also can rate the boat lower than the formula value.