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Running Rough at 3000 rpm

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Sisco Sisk

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A while back I had some problems with my 2000 115hp Tracker Marine cutting out but numerous people on this board suggested that I replace the fuel filter and it made a world of difference. Thanks to all that helped! Although it is running much better now, it's still (and always has been) a little rough right around 3000 rpm. I took my mechanic for a spin and he agreed and thought that the accelerator pump could be dirty or defective. Anybody else have this problem or know what exactly the accelerator pump does?
 

Staci Matheis

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Rob -

There are atvantages to being old! I actually remember what an accelerator pump is! Back when cars had carbs the accelerator pump was a small diaphram that was depressed to inject a little extra gas into the carb as the throttle lever moved forward; it did not function when the throttle lever was held steady.

Now..... I'm not a marine mechanic...... And I've never been into the carbs on an outboard....... But I've played with MANY on 2-stroke motorcycles and they don't have accelerator pumps........

me!
 

Staci Matheis

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P.S.

And not all automotive carburetors had accelerator pumps...... For example, the dual SU side-draft carburetors found on British Leyland products (MGS and Triumphs) didn't have them.

me!
 

Chris Leiting

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Hate to say it but scott YOUR WRONG!!!!!! the 115 Merc as well as the 100 and 125 have an accelerator pump for the 2+2 design... the accelerator pump is suposed to make the transition of running on 2 cyilnders to 4 cyilnders smooth. Yes it could be dirty or defective rob but it sounds more to me like this is the transition RPM which is making it run rough... the 2+2 hates to be run at those RPM, it either likes to idle or run balls to the wall.
 

Staci Matheis

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Thanks, Chris! See, it helps to have a real marine mechanic on the board!

me!
 

Sisco Sisk

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Thanks for the reply....and now that you have brought up the 2 to 4 transition, it's starting to make sense. My understanding is that it should be making the transition somewhere between 18 and 22k not 3k. While taking my mechanic for a spin he commented on how the smooth transition was. Is it possible that for some reason it is not firing on 4 until 3k and if so, is it adjustable? When I'm on plane pulling a tuber or skier at about 27-29 mph my rpm's are right at 3k which obviously makes for a rough ride and sick sounding ride.
 

Chris Leiting

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could very well just need the linkage adujsted, i'd also check your tach to make sure your at 3 grand when the problem occurs.
 

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