I have a 1985 mercruiser 120 that I've been trying to get seaworthy after an overheat. I had the boat running after the initial set of repairs, but it overheated again at WOT during the first maintenance run. The second overheat was not severe at all: I was only in the water for 15 minutes and cut power as soon as I saw the temp guage rise to 175. it cooled quickly at idle. The engine turned over again easily (and ran fine) once I got the boat back home and flushed the engine. Something I did is keeping the engine from starting now... here is the list of things done to address the overheating issue:
Replaced the thermostat.
Replaced the exhaust elbow (due to moderate buildup inside)
I removed the carb in order to remove the exhaust elbow riser. (cleaned riser)
Replaced the exhaust elbow boot
Replaced the exhaust shutter (flapper)
Put it all back together, engine would not start. Cranks fine, Sparks fine, it ran (and started) fine before, so I assumed I did something to the carb when I removed it.
Took the boat to a mechanic to tell me what I did wrong. Mechanic tested the Fuel Pump and told me that it was letting air into the fuel, and should be replaced. I retrieved the boat and ordered a new fuel pump.
I installed the new fuel pump, Engine still doesn't start. Replaced spark plugs. Engine cranks fine, Sparks fine, and now no reason to suspect a faulty fuel pump. I'm back to assuming that I somehow did something bad when I re-installed the carb, but since its 4 bolts and the throttle connections, I'm not too sure how I could have messed it up.
I assume my compression is fine since the engine turned over and ran smoothly before I removed the carb.
When removing the flame arrestor and looking into the carb, I can see that fuel is in the jets, but I've reached the limit of my carb troubleshooting ability.
I'm thinking that I must have messed up something really basic. The carb is a 2 valve rochester with an electric choke. The valve flaps are sitting closed at the bottom of the carb. The only other thing of note is that the screw that rides the cam responsible for the choke plate position was not in the right position when I removed the carb, and I am not sure how thats supposed to be, other than somewhere on the cam.
Any help or suggestions are greatly appreciated! Thanks-