Horsepower Rating?

[Ginder75]

I have heard rumors that the Marine industry changed the way horsepower was calculated in the Early 1980's.

From the discussions I have had, before this time the horsepower rating was at the crank and after this time it was at the prop.

Reason for asking, I have a 1967 35 hp and I am considering upgrading to a 1985 55hp. Will this be a 20 hp increase, a 28 hp increase, ...?

My 35 runs like a top (new points, condensor, rebuilt carb and fuel pump), but it does not have enough power to push my boat the way I want it too. So, I am evaluating my options before I make any impulse purchases.

Thanks for any insight.

 

[Chris1956]

Re: Horsepower Rating?

Grinder, Depending upon the brand of motor you are considering and when they changed over, the increase in HP will be at least 20, perhaps a few more HP

 

[jnewtonsem]

Re: Horsepower Rating?

I'm not positive on this but, I think the HP rating where a "rolling change" as new models were introduced. I've read that they started in the early 80's and continued until about 1990. My guess is that you'd be getting a 25-30hp. increase. reasoning is this: The old 50hp 4cyl. which Merc built throughout the 70's and 80's was downgraded about 1985 to 45hp and badged the "Classic 50". That same motor was downgraded again in the early 90's to 40hp, probably because of unleaded gas issues. The 55hp you're looking at was basically the old 65hp Merc introduced in the late 70"s. Like the old 50hp, Merc again downgraded in the early 90's and it became their 50hp. Using that logic: swapping the motors is like swapping a 35 for a 60-65hp of the same era. Hope this helps.

 

[Ginder75]

Re: Horsepower Rating?

Thanks,

I will be switching brands from Mercury if I get the motor I am looking at. I was scared at first (leaving what little I know). But then I thought about all the people on Iboats that have helped me in the past and I will not be worried about the new motor. But it will not look as good as that old Mercury I have now!