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Old 11 May 2005, 09:32   #1
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Country: USA
Town: Tiverton
Boat name: The Answer
Make: Invader
Length: 5m +
Engine: 135 Mariner outboard
Join Date: May 2005
Posts: 1
Mercury outboard tweaking

Hi got a 93 135hp mariner need to tweak it for some more HP's. I want some more speed out of my boat. I can spin a half way decent wrench but i don't know where to start when it comes to tweaking the carbs. I know that in two strokes "if its lean you scream" but i don't know how far i can go before i pop my motor. i found an adjustment on the top of the carbs that i thought was the idle adjustment circuit. When i fiddled with it i noticed a difference in the performance of the motor. i think it is the lean rich adjustment but i am not entirely sure and I still don't know how far i can go before oeverload. Any advice would be great thanx in advance.

Anthony
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Old 11 May 2005, 09:55   #2
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Country: Canada
Town: Iqaluit, Nunavut
Boat name: Turaagaq -North Star
Make: Bombard WB 385 -2002
Length: 3m +
Engine: Mercury 25 4-Stroke
Join Date: May 2005
Posts: 58
I personally wouldn't tweat it too much, I know that if it's too lean you can burn your motor out but that's about all I know. Maybe you can get some high compression pistons and rings, porting and polishing the heads and intakes. I only have a 25hp 4-stroke but I use an ocatane booster to bring it to 94 or 95 octane. This year I'm just going with a different pitch 4 blade racing prop.
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Old 11 May 2005, 10:18   #3
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Country: UK - England
Town: Farnborough
Boat name: Eleven
Make: Arrow
Length: 8m +
Engine: 557cu, 700hp
Join Date: Jul 2003
Posts: 1,255
Tweaking Merc V6's : www.screamandfly.com
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Old 11 May 2005, 14:16   #4
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Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
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Quote:
Originally Posted by tonyjd
Hi got a 93 135hp mariner need to tweak it for some more HP's. I want some more speed out of my boat. I can spin a half way decent wrench but i don't know where to start when it comes to tweaking the carbs. I know that in two strokes "if its lean you scream" but i don't know how far i can go before i pop my motor. i found an adjustment on the top of the carbs that i thought was the idle adjustment circuit. When i fiddled with it i noticed a difference in the performance of the motor. i think it is the lean rich adjustment but i am not entirely sure and I still don't know how far i can go before oeverload. Any advice would be great thanx in advance.

Anthony

Take a look at some of the off-road motorcycle sites for 2 stroke tuning tips. Realize, though that boat engines tend to be a little different than bike engines in the way they deliver power (i.e. you generally want a smoother power curve on a boat vs. a bike where you want a high top end.)

That said, if you don't really know what you're doing you'll most likely cause more problems than you solve.


jky
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