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2002 mercury 115 hp 4 stroke running rough

J

jolley

New member
"some one please help? I have an 02 115 mer 4 stroke. It idles very rough after startup and stalls or sometimes hesitates during acceration and stalls during fast deceleration. I have had the vst serviced and cleaned the fuel presure on the rail is 38. the compresion is 140 psi there ais no water in the fuel I have a 10 mic ron fuel feul seperator plus the on on the engine are also new. HAD THE DEALERSHIP RUN AN DIAIGNOSTIC CHECK AND THERE ARE NO CODES. Beside s that nothing is wrong. I also have a small power loss I can only get about 4800RPM IN GEAR and before i got max rpm 5000 - 5600. i never change the prop. checked oil level fine not running hot, Has anyone had this problem before or dose anyone have an idea on what this might be please feel free to talk. need help"
 
"John, unfortunately 4 strokes

"John, unfortunately 4 strokes are still "new enough" that quirky issues like yours are not well recognized, at least by most of us who work out our garages and backyards.

Despite the lack of codes I would suspect the MAP sensor since all your symptoms are indicative of a manifold pressure problem.

At close to 250 bucks, the MAP is not something you simply want to swap out to see if it fixes the problem.

I have no idea how the motor would run (at anything above idle speed) if you simply disconnected it in an attempt to check.

The ECU will "pretend" that is still there but I have no experience as to whether it would allow the motor to run well enough to do a test run to see if hesitation/stalling issues would be corrected.

However, if you are experiencing the rough idle and it smooths out upon disconnecting the MAP, that is a pretty good indicator that, that particular sensor is the problem - codes or not..."
 
this is the same ting as the a

this is the same ting as the air presure sensor right? becuase in the book i cant find were it says MAP. I just want to make sure that I unpug the right one.
 
"oil level needs to be halfway

"oil level needs to be halfway up dipstick not to the top of XXXXXX marks

could be valves, plugs, fuel filters, or even not synced right

better find a certified outboard tech"
 
"oil level is fine, valves hav

"oil level is fine, valves have been checked, new plugs with the right gap, new fuel fillters. What do you mean synced right I thought that ment synced carbs? if so i do not have any i have an efi sytem. If you are talking about timing I will try to do that tommrow.I had it at the dealer over the weekend and it left them confused."
 
clys 1 & 2 are fine but 3

clys 1 & 2 are fine but 3 and 4 are wet but firing. they smell like fuel. dose this mean that i need to have the throtle body synced?
 
"Thanks for the advice,you wer

"Thanks for the advice,you were right about the injectors. # 3 was stuck and 4 was starting too. I got the power back but it still wants to run rough and serge at idle. Do you have any more ideas? Still no codes on the blinky light. Fuel presure is 40 psi on the rail."
 
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