1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

[larrye44]

I have a 1998 Yamaha F50TLRW that Runs Rough and Carbs were run dry before storage? I always run them dry when I put it up for a couple of month. It always starts right up and no problem. This time is runs real rough. Sputters and spits and backfires a little (more like a smoker's cough). I bought a new fuel tank and eliminated contaminated fuel. It runs the same way on the new fuel. It tries to run smooth every so often like the carbs are clearing up but not all the way. Any ideas what this might be? I don't have that much experience with outboards. Thanks everyone, Larry

 

[99yam40]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

You cannot run the carbs completely dry as there is always some fuel left in the bowls. I always leave them full just making sure there is proper additives in fuel, and run as often as possible to keep it fuel from dying out. That and the fact that all of the bowls will not run out at the same time meaning you are running some cylinders lean on fuel before the motor finally dies
As the fuel evaporates there will be a thin film left in the bottom of the bowls, lines, and pump which will find its way into the jets. Sounds like it is time to pull and clean the carbs before you cause some damage to one or more cylinders due to lean fuel problems

 

[larrye44]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

Went through the carbs and all four are clean and no varnish. Cleaned the 15 gallon fuel tank, fuel line and fuel filter and put in fresh gasoline that is ethanol free and added 1 and 1/2 oz. of Ringfree along with Stabil additive. Tried to isolate which cylinder was the problem by removing spark plug wire while engine was running. Rough running is intermittent and was not able to tell which cylinder it was. Took it out and ran it. At 4000 rpm's it runs very smooth. Slower speeds and WOT it runs rough, but seems to idle real good. Someone told me that it may be a coil pack. Is changing the coil packs something a person with some mechanical skills could do? I see in my Clymer manual the ignition coils are easy to get to. Any ideas on this is appreciated. Thanks again everyone. Larry

 

[99yam40]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

Did you go through the carb sync like the manual states after reinstalling?
From what I understand it requires a 4 tube manometer to do it properly.
With the proper equipment the ignition (spark producing) voltages can be monitored at problem RPM to see if they are a problem or not

 

[larrye44]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

Yes carbs were sync'd at the dealership 4 months ago when they rebuilt the carbs. When the problem started again, a mechanic friend went through carbs to eliminate any varnish and there was none. So, do you think I need the dealer to take a look at the coils?

 

[99yam40]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

Testing the electrical is easy to do to pinpoint any problems with spark, even at the problem RPM and load with the proper test equipment. If no problem is found with that then work on the fuel

 

[larrye44]

Re: 1998 Yamaha F50TLRW Runs Rough and Carbs were run dry before storage?

Thanks, 99yam40, I think I had better take it in for the dealer to look at. I don't want to start part changing. That can get costly quick and they have the right test equipment for the job. Thanks for the help. Larry