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Mercury 125 2+2 Not fully accelerating

R

Radioraffa

New member
HI there I have a 2004 merc 125hp on a 22ft aluminum deck boat. When WOT .. Doesn't seem 3&4 are getting any fuel maybe hitting 10 mph. I have changed the filters, spark plugs, checked water separator and inside parts of accelerator pump. No change. This did start after changing the first ( larger ) filter. Removed it and put in a strait tube to bypass.. Still no change. Any suggestions ?
 
Check compression and confirm spark to start with.

History may get you a better starting place answer.

History?

Was running fine until....

New to you motor and you don't know if/when it last ran ok?

Ran fine last year but acting this way since coming out of storage?
 
"New to me" motor. I bought it in February . Was running fine until one day it just sputtered out.. At the time i knew i was low on gas and my gas gauge was not working. So filled it with gas and then would not start... Afterwards I changed the parts like I said in the original post. It appears to run on low speed fine ( no wake out the canal ) but when I give it full throttle it will only go about 10 mph. At no time does it sound like 3&4 engage. When idling with the cover off I will press down on the accelerator pump button but there is no change in sound or RPMs.
 
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If you added the gas after she gagged out there is a chance that you sucked a bunch of crud from the tank into the line, filter or even the carbs.

That's where I would start looking for the issue before moving on to more labour intensive trouble shooting.
 
Yes.. Thought about that too.. That's why I changed the parts in the fuel system. My issue is that carbs 3 & 4 are not opening. Looking in to the check valves next.
 
I have a 94 2+2 but mine feels like is wants to go but just won't kick in and tank have been Drained Replaced all filters and fuel pump and cleared lines. Mechanic said it ran fine. I just got home that was a d*** lie. The only thing that I haven't replaced is the accelerator pump
 
When you said "filters", did you get the large one on the port side of the engine and the small one on the Starboard side of the engine to the rear of and behind the oil tank? Pull all 4 plugs and look at their condition. If 3 and 4 are wet then you are getting fuel but they are fouled. Install new plugs and when running below 1800-2000 RPMs tilt the rear of the engine up 10* to keep fuel from puddling at the rear.

I have a 2002 115 and I notice an increased speed and smooth operation immediately when I do that. Also when I punch out I get immediate response on 3 and 4. Well you say 3 and 4 aren't exploding so where does the enhance come from? Must come from 1 and 2.....but I get it every time I do it and the punch out is faster and smoother. I hit about 3/4th throttle and the 2002 Crestliner 1750 fish hawk jumps on plane with a 22 pitch Ballistic 3 blade prop.
 
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