89 100 hp merc won't run.

[nohandsjoe]

Hello all, I am totally stumped. I have a 1989 100hp 4 cyl. outboard that I have been having trouble with. It started this spring when it died while I was fishing. I rebuilt the fuel pump and did find a tear in one of the diaphrams. I ran it for a short time and it seemed to be missing on one cylinder. I changed the plugs and put a little Seafoam in the gas. The motor will start and idle great for about 5 seconds then die and is hard to get started. It acts like it is running the fuel out of the carbs and then dying. I took my carbs apart and cleaned and checked them and all seems well. I have replaced the fuel pump, I didn't trust my rebuild job, and it still does the same thing. If anyone has an idea of what to check next, I would really appreciate it.

Thanks,
Joe.

 

[starcraft1982]

Re: 89 100 hp merc won't run.

Testing is everything.First,compression.Next,spark.Have to have three things to run.Good compression in all,good spark to all,and good fuel to all.When/if compression and spark checks good,"tear"into the fuel.If it were me,I`d replace the fuel lines,bulb,and quick connects.Ethanol will do a number on lines if theyre older.Use only merc(metal)quick connects.The plastic junk will not hold up.Check vent to fuel tank for obstruction,if portable tank,make sure its open!Then,if still a problem id REBUILD carbs using all new gaskets,needles and seats.Also if floats are old(cork)type replace w/new as they can crack and become saturated w/fuel.I would say check fuel pump but would doubt its an issue since a rebuilt one AND new one didnt help.Good luck.

 

[nohandsjoe]

Re: 89 100 hp merc won't run.

Thanks for the quick response Starcraft1982. I did try new fuel line today with no luck, I have confirmed spark, and compression, both were good, the motor was completely rebuilt 2 years ago including new kits in all the carbs. I took the bowls off of all 4 carbs and they looked perfect so I put them back on. I thought I had found a problem with the fuel, but confirmed that wasn't the problem today. I have decided now to take the carbs back off tomorrow and go through them completely just to rule them out. I'll let you know the outcome. I'm not very optimistic.