I could use some good fuel supply advice

[rg2]

I have a 1999 25 merc 2 stroke. Since I purchased the motor last summer it just hasn't seemed to run right. Last summer it would start and idle fine but between idle and wot it would act sluggish and often die. This year I noticed that it didn't seem to have the same amount of power at wot, it almost seem to slow as though you were letting up on the throttle then slowly gain speed again. I checked compression on both cylinders and the results were 90 and 100 psi. I removed the carb to clean some sand/dirt from around the area where the carb is mounted. I removed the float bowl and checked for varnish/dirt. There was none. I replaced the spark plugs. reinstalled the carb and got the motor started. It ran for a short time and then died. I could not get it to restart. The next day I installed a new float bowl needle and adjusted the float itself. I could get the motor started and it would run for a few minutes then it would stall again. restart it, idle awhile, stall. Over and over. Anyway I really can't afford a mechanic right now so I would really appreciate some advice from you experts out there. Thanks.

 

[CharlieB]

Re: I could use some good fuel supply advice

First thing is pull the fuel line off the carb, point it into a suitable container, squeeze the primer to verify fuel, then hit the starter and watch for the fuel pump pulses, does the pump work?

 

[will941s]

Re: I could use some good fuel supply advice

You need to get a carb kit and completly tear down and clean the carb...everything...inside and out, then blow it out with compressed air. Put all new gaskets, seals, fuel pump, and primer (all included in the kit for under $40). Then you know the carb is good clean and tight. Next, buy some new fuel line (for the motor) and install it. Go to wally world and get the Attwood fuel/water separator ($28) and install that. Then you know you have good clean lines on the motor, and good clean fuel going to that nice clean carb. Last....lets say your timing on the motor is where it should be, on the air resonator box on the front of the carb, remove that little plug. Tighten the idle mixture screw all the way in til it lightly seats. Back it off 1 1/4 turn. Attempt to start the motor, back it off or screw it in slowly (no more than 1/4 turn) from that initial 1 1/4 in either direction til it starts and runs. Now.....with it running, slowly back it off (lean) til it begins to run rough. Then slowly tighten (richen) until it begins to run rough. Back it off til it runs right and starts right, thats your sweetspot. And you always want it on the rich side. BTW...do this IN water, not on muffs, you need that backpressure to get it right. Now, if that don't work....you need to have it linked and synced. They adjust the carb to the timing..and it's not all that expensive.

 

[rg2]

Re: I could use some good fuel supply advice

Will941,

It's funny you mentioned the link-n-sync. I asked the local marine mechanic about that the first time I had trouble with it not starting at all and he said that I didn't need to be concerned with that since I only had one carb?? Can you explain or direct me to a explanation of this procedure and what its purpose is. The mechanic also told me that if I dropped the float bowl and it was clean then I didn't need to worry about the carb because the rest of the carb would probably be clean as well. He said that if the problem exists it will show up in the bowl first. What are your feelings about the compression figures I gave? Do they seem ok? What are some of the tell-tale signs of low compression? Thanks again - if you can't tell I really find this stuff interesting - I just wish I knew more about it.