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Old 04-06-2012, 13:02   #1
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Uprating the power on outboards

I have a mariner 4 stroke 8hp outboard motor which is pretty heavy but a good engine.
I was told that the 8hp and 15hp versions are essentially the same and if I got new jets I would have 15hp.
I have no idea if this is true or not and wondered if a lot of engine manufactures douse the same engine and with a little know how it can be uprated.
Can anyone shed any light?
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Old 04-06-2012, 13:08   #2
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Re: Uprating the power on outboards

I have no idea about that. Have a friend who is an outboard mechanic and he talks a lot about boring out the exhaust on 2 strokes to help performance.
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Old 04-06-2012, 13:21   #3
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Re: Uprating the power on outboards

Larger jets and a mixture adjustment would give more power but I can't see that much improvement. You would probably need to change the whole carb and then it would only give that much if the engine was a restricted 15hp.

I recently went from a 5 ho Honda to 10 hp Yamaha (both 4 stroke) and I was really struck by how much more fuel I'm using. It is a lot faster though.
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Old 04-06-2012, 13:27   #4
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Re: Uprating the power on outboards

Its a boy thing or a man's toy. Either way we never grow up.
If I can double my engines power and give the wife a face tuck at the same time when trying it out we will all be happy.
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Old 04-06-2012, 14:16   #5
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Re: Uprating the power on outboards

Quote:
Originally Posted by Nostrodamus View Post
I have a mariner 4 stroke 8hp outboard motor which is pretty heavy but a good engine.
I was told that the 8hp and 15hp versions are essentially the same and if I got new jets I would have 15hp.
I have no idea if this is true or not and wondered if a lot of engine manufactures douse the same engine and with a little know how it can be uprated.
Can anyone shed any light?

It is all in the carb. You can google or yahoo this, and there is a lot of info about these questions and motors. Same for most small 9 - 15 outboards.
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