I bought a 62 or 3 5.5 Evinrude. It had been sitting for decades and it looks like it has very few hrs on it. I started it up and it ran OK for a little while and then it started running erratic. Wouldn't idle, then Lean,rich,lean,rich and so on. I'm guessing I need to pull the carb apart, but I'm wondering how often the crank seals go on OMCs from sitting. From what I understand an old motor that has been sitting will run OK for a while and then the crank seal(s) will fail making them impossible to idle. Help!
Well the good news is your motor doesn't have crank seals! You may/probably have cracked ignition coils. You can pull the rewind starter & I think that model will have an inspection plate. Remove it to see the coils. If they are cracked you will have to replace them. Even if they look good they may be breaking down after they get hot. Testing procedures & R&R are on You Tube. Stay away from the Sierra brand as they aren't fitting too well at the moment unless you want to use your old laminates.
I know that's a weak point on OMCs but I would still say it's fuel. The spark is hot on both cylinders. I suppose the plugs could have enough spark outside the motor but breaking down under compression? That happens in the automotive industry. No crank seals? Do the larger OMCs have them? I thought I remember a carbon seal on the top of my old big twin but not sure.
I wouldn't call it a weak point! All good things come to an end after 60 yeras. I'm 64 yrs old & still here, but I've had a few new parts installed. Yes the Big Twins have a carbon seal on the bottom, but the 5.5 & 7.5 just had a cork gasket that is pushed up by a spring arrangment on the driveshaft to seal against the bottom of the crankcase. Worked fine for many years. The top has a slinger that keeps the oil off the ignition components. Remember enough spark to jump .030 in open atmosphere may not be enough to jump under compression + those old coils may break down after they heat up? The fact that the engine starts & runs signal that the fuel system is working. It may still need repair to work at its optimum. Again remember your fuel carries your oil in a 2 stroke. Better to run that motor at 24/1 minimunm. Most like 16/1. I don't remember if that model has needle bearing rods?
You have to pull the powerhead to replace the water pump. Not a big deal (unless used in salt water), but some consider it a hassel. Just part of the way it was. The whole assy. comes off without much disassembly except maybe a choke knob or needle. Hope that helps!