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Author Topic:   Change in Horsepower Ratings
gnrgunner posted 08-06-2001 08:11 AM ET (US)   Profile for gnrgunner   Send Email to gnrgunner  
Has anyone heard about the change in horsepower ratings in outboard engines within the past 20 years? Evidently, older ouboard horsepower was the amount of horsepower in the powerhead. Newer engines are now rated by the amount of horsepower generated by the driveshaft. I had a 1981 35 hp Evinrude that ceased while on my vacation forcing me to replace it. I ended up buying a 1993 25 hp Evinrude in great shape (not as much horsepower as I would like to have, but a good temporary replacement). I stripped the old engine before taking it to the marina, taking out the spark plugs, cover, and prop. I then put prop that was on the old motor onto the new one. The old 35 used to get me up to about 33-34 mph at full speed on the highest trim setting. The new 25 also gets me up to 33-34 mph at full speed on the highest trim setting. This means the extra 10 hp on my old engine did absolutely nothing. When I ask my mechanic why this was happening, he told me about the change in hp rating. Does anyone know more on the subject, or when this change might have occurred, or was it more gradual with all companies doing it at different times? Thanks
Bigshot posted 08-06-2001 09:50 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I said that on your last post that the newer 25 would be close to your 35. OMC did the change in 85 I believe. Merc did it earlier and JAPANESE manufacturers have always rated at the prop as far as I know. This is why you see people recommending 30hp or 25's on older blue hulls. This is also why we have ongoing debates on overpowereing a classic and the new 4 strokes and weight differences. It is interesting the way it works.
Tom W Clark posted 08-07-2001 10:21 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
BS is right. By the mid 80's all the manufacturers had switched over in order to stay competitive with one another but the max h.p. ratings for the boats never changed. This has always surprised (and delighted) me. We all got a little bonus if we wanted more power. I've never met a 13' that didn't love to have a prop shaft rated 40 hp motor on the back nor a 17' that wasn't perfectly happy with prop shaft rated 90 (faster than than the old, and formerly taboo 115's)
Mullet posted 08-07-2001 10:50 AM ET (US)     Profile for Mullet  Send Email to Mullet     
Not only does a 13 like a shaft rated 40 the 21 is in Heaven with a shaft rated 200.
Bigshot posted 08-07-2001 11:12 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Yeah but where do I find a 170hp for my old 1974 19' revenge:)

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