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New verses old motor power

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maaswhole

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"I am replacing a motor on an

"I am replacing a motor on an older boat. My buddy says it will be over powered, even though the boat is rated for the 90HP I'll be putting on it.
Are new 90HP motors stronger than old 90HP motors, or are they both 90HP?"
 
"If it's rated for 90 hp,

"If it's rated for 90 hp, then it will take 90 hp - no problem. BUT - you may want to consider any weight difference between the old and the new. If newer is substantially heavier, then you could be moving the boat's center of gravity more toward the stern, which may cause handling problems."
 
"Thanks for your comments. It

"Thanks for your comments. It just seemed like the old riddle, what weighs more, a pound of gold or a pound of feathers?
The transom is aluminum and I changed the plywood piece where the bolts go through, so it's like new.
So we agree, my buddy is wrong, a 1970 90 hp motor put out about 90 hp, and a 2000 90 hp also puts out about 90 hp?"
 
Maybe he's thinking about

Maybe he's thinking about thrust or some other factor that might have increased over the years?
My brother in law collects old boats and all his stuff goes like mad!
 
I think the difference from ol

I think the difference from old to new is the older motors hp was rated at the flywheel and the new motors hp is rated at the prop.
 
"Yes, the 1970, 90 horse was r

"Yes, the 1970, 90 horse was rated in Brake Horse Power (BHP), but they were a little loose with the ratings as well - no EPA looking over their shoulder back then.

A 90 BHP would roughly equate to between 82-85 Shaft Horse Power (SHP) the modern measure.

But if they were off by say 8-10% in the first place, that 90 BHP may have been putting out as much as 99 horses, which when converted to the modern standard would still be a 90-95 horse motor.

A new motor will usually have less than a 5% variance from what the decal says. That way they get the EPA stamp of approval for emissions.

So basically, anything less than 100 horses, whether old or new, would be putting out similar horsepower....

If you look back through the mid 80's you will notice a couple of models that "went away" or changed.

If you look for a 150 Evinrude, you will see the following year they marketed a 135 model - same motor, they just adjusted the rating to reflect the SHP numbers."
 
can anyone help me? i have a m

can anyone help me? i have a mariner 50 hp. ser# 5964738 can anyone tell me the year? please.thanks
 
"Sammy, you should have posted

"Sammy, you should have posted in the Merc section and under a new link.

But anyhow, that's a 1981, Mercury Mariner, 4 cylinder..."
 
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