i have a 175 merc and my buddy has a 200with a trophy 25 4 blade he turns 6k and runs 72 i put his prop on and turned it 6k and only get 64. does 25hp make that much difference? exact same boat only diff is his motor is 3/8in lower. i just think my boat should perform a little closer since i am turning his prop the same as he is. any input would be greatly appriciated.
Well there are a lot of variables. Usually in my experience 25 hp will be about 3-4 mph faster. That being said there are many other variable as well. Your gears could be different, you could be loaded heavier or have more weight up front than he does, and your motor being higher you might have more prop slippage. 3/8" makes a big difference. There is also that famous 10% rule on hp. I am no expert but you should be sure you are comparing both with the same setup and load.
Alan
Chad St. Pierre
Paulina LA 70763
You might have a different gearcase ratio as well. His 200 is probably a 1:87 where your 175 could be a 2:00 which would give about the same revs as his but with less speed.
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