Re: motor rating capacities on boats
Last I looked, horsepower rating based on a few different principles, but not too terribly complex. The first was a simple formula based on the dimensions of the boat. For mono-hull boats under 20 ft in length, the formula is:<br /><br />(2 X L X W) -90 = rated horsepower<br /><br />Where:<br /><br />L=boat length<br />W=transom width; if the boat does not have a full transom,<br /> the transom width is the broadest beam in the<br /> aftermost quarter length of the boat.<br /> <br />The rated horsepower may be rounded up to the nearest "5".<br /><br />So a 19ft boat with a transom width of 6ft 6 inches should have a maximum HP rating of (19x6.5x2)-90 = 157hp, or 160hp rounded up.<br /><br />Now, a secondary test is a high-speed turn test. A boat must be able to handle a sudden 180 degree turn of the steering wheel at maximum speed with the max horsepower engine (propped correctly) without loss of control or ejecting the driver. If the hull design fails this test, the manufacturer can either lower the horsepower rating, or place a warning label on the dashboard. I believe most opted for de-rating.<br /><br />If anybody knows of additional requirements, or my information is innaccurate, please correct me. I found this information because I needed the info, and I would appreciate correction if I am in error.
<br /><br />I think you're right about the Bayliner ratings. They put them together as a package deal, with a smaller motor for safety, reliability, and probably cost as well. Then just slapped the rating on there to match, even though it may be able to handle more. Every other 19ft boat I have ever seen is rated for more than 125hp.
