Rough running Merc

[Dough614]

02 150 bluewater series, for about the last 6 months the motor would run good on and off, I started having problems with the motor running smoothly after I would trim it up to get bait. then it would struggle to start and run, would have to have full throttle to start and work the throttle to keep it running. wouldn't idle either. Well I took the carbs apart cleaned them new gaskets. had a few clogged ports thoughout the 3 carbs. took it back to the water the next weekend, had probems with overheating this time. brought it back took the thermsostats out, clipped the springs out reinstalled the the thermostat caps, there was no movement on the springs and some corrosion build up on the right side. Replaced the impeller. No more overheating problems. Took back to the water again. it ran perfect for the first 4 hrs, then when I trimmed up to get bait again it started running like it did before, full throttle to start, working the gas to get to run, couldn't keep running to load on the trailer. I'm almost out of ideas, any ideas?

 

[sschefer]

Re: Rough running Merc

I would do a primary and secondary compression test. The primary is done on the crankcase, the secondary is done on the cylinders. Check the manual for the specs for your engine. Let us know what the results are and we'll go from there. Without these preliminary checks any other advice is speculation.

 

[Dough614]

Re: Rough running Merc

Question, if it will run smooth for 4 hrs, how does compression come in to it, after I trim the motor up, and put it back in the water? then it runs like crap.

 

[Dough614]

Re: Rough running Merc

cmon you guys are letting me down.

 

[sschefer]

Re: Rough running Merc

LOL... Fine, go get a manual.

 

[Dough614]

Re: Rough running Merc

not really what I was going for

 

[sschefer]

Re: Rough running Merc

Maybe not what you were going for but its a heck of a good place to start. LOL.. Actually, the symptoms you describe are the same symptoms I experienced once. The reeds were bad and to compensate for the roughness I set the idle a little higher with the throttle stop. What we decided was that with the throttle cracked and the bad reeds when the engine was tilted the fuel was drying out of the crankcase and leaving and inadequate mixture to burn. If I hit the choke and opened the throttle wide open it would start after some long cranking and then run o.k. but the idle was still rough.

With the engine veritcal the fuel had less tendancy to dry out through the slightly open carbs. Anyway, replacing the reeds and correcting the throttle fixed the problem. We figured out the problem by doing a vacumm test on the crankcase. That's what is also known as a primary compression test.

 

[milehighboater]

Re: Rough running Merc

When you tilt it up do you take the motor all the way up? The reason I ask is because of the fuel disconnect comming undone or loose and letting air into the fuel system. When you tilt up the motor it puts a good amount of strain on that fitting. but if you reconnect it gets reseated. just a thought.