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Old 16 April 2006, 10:35   #1
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Guys,
I'm after buying a used 30hp outboard to replace my worn out, old 25hp Evinrude. I've been told that a 25hp engine built prior to 1995 will only give me about 18-20hp at the propellor, whereas a modern engine will give me 25hp at the prop. Is this correct?

I'm wanting to up the engine size so I can tow a wake boarder. Would a 25hp Yamaha autolube on the back of a 3.5m jockey console rib do the trick?

Cheers,

Happy Easter!
Tim.
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Old 16 April 2006, 10:43   #2
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I don't know the answer to your question but as somebody who deals in mechanical things a fair bit I'd be astonished if anything is 100% efficient! unless the ratings have changed from "engine rating" to "prop rating" if you see what I mean
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Old 16 April 2006, 13:25   #3
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Quote:
Originally Posted by Northern Tim
Guys,
I've been told that a 25hp engine built prior to 1995 will only give me about 18-20hp at the propellor, whereas a modern engine will give me 25hp at the prop. Is this correct?
The HP ratings were changed earlier than that but you're correct-Mercury went over to prop-rated HP in around 1988 and sold their old style 50's as 45's. Not 100% sure when Evinrude/Johnson did but definitely before 1985.

Bear in mind that stated horsepower is only a guideline and can has to be within 10% of what is stated on the cowl so a 30 could be from 27-33hp. Essentially, do your research thoroughly...
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Old 17 April 2006, 05:35   #4
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Quote:
Originally Posted by Northern Tim

I'm wanting to up the engine size so I can tow a wake boarder. Would a 25hp Yamaha autolube on the back of a 3.5m jockey console rib do the trick?
might well do I have manged to tow a kneeboard with a 25hp 4stroke on a 4.3 rib??? but my son is only about 8stone.

borrow a wake-board and see what happens.
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