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

me!
 
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.
 
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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