I have a 78 Evinrude 35hp on a 1963 13' whaler. I took it out last week after I bought it and had it running and it ran great after I played with it in the driveway for a while. Once out on the water it ran great but tended to cough and spit on idle and it wasn't real smooth. It hadn't been run in a long time. It wasn't pumping real great and the local boat yard mechanic said they are famous for a stuck thermostat. He pulled it out and repalced the head gasket too at the same time. Once again it ran great in the driveway but I got it out and it ran ok but then started up again coughing and sputtering and then fouled the plugs. I put in a new set and it ran ok for about 15 minutes and fouled them too. Did the same with a 3rd set.
The only setting I see it the low sped setting and I was told to start at 3 turns. It runs turned down to one turn and all the way up at 3 turns. It really is strange. It runs like new with new plugs then go to heck in 10-15 minutes.
I ran QL77JC4 plugs and L78V plugs and it did the same with both. I am thinking it's a carb problem. I did notice that the last time when I opened the engine cover there was some fuel that came out of the front of the carb along the airbox.
Any suggestions as to where to start is appreciated. I bought it knowing there were issues. The previous owner was told by the big boat dealer in Norwalk that it had a bad crank seal but the thing has 140PSI in each cyl which I though it would never have with a defective crank seal. Not sure how to tell if this is the problem or if they just didn't want to work on a 1978 outboard. Any idea what the symtoms of a bad crank seal are?
It's too good to throw away...help if you can...Thanks!
Re: 1978 Evinrude 35 hp long shaft won't run right
Throw those L78Vs away. If the lower crank seal is bad, it's difficult to tell without pulling the powerhead.
A bad crank seal won't show up in a compression test. Try a cylinder balance test by shorting out the spark plugs (at fast idle) one at a time and see if RPM changes more with one than the other. The one with least change is the weak one and the seal could be the cause.
Coughing at slow speed indicates a lean condition, or a too cool condition. A bad crank seal admits air, also causing a lean condition on that cylinder. Try turning the needle to the left a bit. Or it could be a carb problem.
What appears to be fouled plugs aren't necessarily really fouled. They can look like crap and still be OK.
Re: 1978 Evinrude 35 hp long shaft won't run right
If you are spitting fuel out the front of the carb take it off and look into the reed valves for something in there. My boat was running great on Saturday when all of a sudden it felt like I dropped a cylinder. Took off the airbox and carb because I thought I might have had a stuck float but looked into the reeds and one of the bolts from the airbox had come loose and it was back there. Ten minutes later we were cruising again.
1978 Evinrude 35 hp long shaft won't run right
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