Horse power rating formula.

[oregonducker]

Link suggested that my question/comment regarding this from another post should have it's own thread. Good idea. Here it is.<br />

Is that really it? L x W x 2 - 90 = hp rating? So my 14 foot aluminum with it's 6' transom would be rated at 78 hp?! I know a motor that big would be way too heavy to say the least and the actual rating plate only says 35 anyway. I always figured there was more to it than that. Such as hull material and construction style or whatever.<br />

Here's the link to that formula as provided by phatmanmike.<br />Here's what Link added to the question.<br />

How do you compare a 14ft car topper with a 6 foot beam weighing in at 80-150 pounds to another with the same deminsions that clocks in at 400 pounds with a 26 inch transom and 30 inch free board..

Exactly the kind of thing I was wondering. Two boats could have the same dimensions but be constructed with very different materials and methods. I know the formula is only a guideline and not law but in the cases stated above it's pretty wacky. I used to have a much smaller 14' boat. It's beam at the transom was 3.5' which would give it an 8 hp rating. That one makes sense.

 

[snapperbait]

Re: Horse power rating formula.

This is much more accurate.. http://www.herknperk.com/HTMLobj-1743/USCGPamphlet.pdf <br /><br /> It's more than length and width.. Bottom design and transom height are the major factors...

 

[phatmanmike]

Re: Horse power rating formula.

it makes me feel all cozy and fuzzy inside when i do good and people notice <br />

Here's the link to that formula as provided by phatmanmike.<br />

ive been trying to get the moderators let me post that as a FAQ topic, but i guess they have other things to do.....

 

[scott begovich]

Re: Horse power rating formula.

According to that formula, I am overpowered just a tad 23.5 x 6.5 = 152.75 x 2 = 305.5<br />Actual HP 565 - 305.5 = 259.5 HP too much<br />

 

[Jdeagro]

Re: Horse power rating formula.

Try using a Hp to Weight Ratio of between 10 lbs per 1 HP and 14 lbs per 1HP. Obviously the 10 to 1 is a higher performance boat.

 

[scott begovich]

Re: Horse power rating formula.

This is getting fun 3800lbs 380hp<br />565-380=185 only 185hp over with that formula.<br /> <br /><br />Seriously, I think this formula will work better with the smaller aluminum boats.<br /><br />My boat is used for racing and pleasure so naturally I will be on the high end. I think props should somehow be taken into consideration as well as gear ratio. My boat reacts completely differently with respect to top end, stability, and accelleration with 3blade vs 4 blade vs 5 blade props.<br />These Formulas are good to keep you in the ballpark and if your way off it should just be a red flag to do a little research