1999 merc 40hp 2 cyl bogging problems.

Bvrj0969

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Joined
Sep 25, 2016
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3
1999 or 2000 merc 40 hp 2 cyl engine

Serial number 0g963884

Just bought a 99 fisher dominator with this engine on it.

Background.
Boat sat for a few years.
Boat would start but wouldn't run over an idle. Found cracked fuel line running to primer solenoid. Replaced line. And new gas. It would then Start/run and had a few good outings on the boat. Would rev 5200-5400 rpm. Start easy ran smooth etc.


Then one day put it in the water. It started great. Ran great at WOT for about 5 minutes. Then it bogged down and shut off. Started back but wouldn't rev over 2000 rpm under a load. Any more throttle and it would die out unless the throttle was cut back. Unless you Push the key in and it would pick up to 3000k sometimes 4000 rpm but only for a few seconds..

Here's what I've done so far.
Sea foam in the tank.
Pulled carb and somewhat cleaned with carb cleaner and reassembled. (I couldn't figure out how to get the float pin out)

Pulled fuel pump and disassembled. No rips or tears but one of the clear round prices did seem to have a crease in it making it hold open farther than the other.

Also pulled plug wires on it while it was running. (This part seemed odd to me)
Pulled one. Didn't make a difference. Pulled the other, it died. So I swapped the coils around. Tryed it again to see if the problem moved. Both of them made a difference this time. Started miss firing when pulling each off.

Took it out again. Ran great for about 20 minutes before doing the same. Now it Will let you throttle up to around 2200 rpm before it will bog down and try to die.


So what's the next step?
Redo it all? With new fuel pump kit and actually tear the carb all the way apart?

Or coil cutting out when it gets warm?
How can I test?
 

DavidMoore

Petty Officer 2nd Class
Joined
Jun 2, 2015
Messages
183
Redo it all? With new fuel pump kit and actually tear the carb all the way apart?

- Yep. and change all the fuel lines at the same time. Chances are that the fuel lines are deteriorating, just a tiny piece of fuel line rubber in the carbs can cause exactly the problem you describe.

Or coil cutting out when it gets warm?
How can I test?

- Timing light or better still spark gap tester
 

Bvrj0969

Recruit
Joined
Sep 25, 2016
Messages
3
Will try.

Tbh the carb looked great inside but that's not to say I missed something.

Any ideas on how to get the float pin out? I could see where someone used a punch to knock it in and out. Guess I follow suit?
 

Bvrj0969

Recruit
Joined
Sep 25, 2016
Messages
3
So far a lot of dryed/charred cracked lines. Will replace and reclean carb and see what happens
 
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