1977 mercury 850 thunderbolt will not start

[speedylb]

hey i just got this engine and boat, trying to figure out how and why this engine will not turn over. i turn the key and it sputters and acts like it wants to start, occasionnaly it will misfire but not turn over. would some help on this issue. thanks

[Yepblaze]

Fist off when you say "won't turn over" any of us with half a wit to-wards mechanics will consider the fact that the engine won't rotate by way of the starter.

Now myself being slightly psychic have visions that perhaps what you are trying to say is.........

That the engine rotates or turns over with the starter, but won't quite catch and run on it's own.

Or maybe it won't even start to catch, but might give some indication that it wants to run but just doesn't.


Perhaps you try using the choke while turning it over with the starter.

[speedylb]

yes the engine turns over but wont catch and start, hope that makes more sense. the manual choke doesnt seem to work or the push button one either any other suggestions.

[speedylb]

the flywheel does turn when i try and crank it over.

[jimg984]

could try spraying gas/oil mixture into the carb openings

[jeff_smith_0423]

Hey speedy. I have your exact same motor but i'm not an expert on it or any outboard by any means. Ask the right questions around here and you'll get all the info you need. If you're going to seriously consider using this motor, you should get a factory repair manual or a Seloc manual if you can't find one.

A few things you should do before seriously running your motor - Go through the "Reviving an old outboard" faq that's posted on this site.

Your motor is a two stroke, and it depends on three things to actually fire and run. Compression, Spark, and Fuel. If all three are there, it will run. Will it run well? Maybe not, but it'll at least catch and fire.

Your motor should have a manual choke knob that you can pull up and activate the choke. If your electric choke isn't working, I'd probably suspect that your wiring harness is rotten or you have rotten wiring in your control box. I'm assuming that you did not hear this motor run before you got it - that being said, you really need to start from scratch with the revival process, inspect all of the wiring, check compression, spark, and inspect your fuel pump and carburetors. They will most likely need to be rebuilt and you'll probably need to replace all of your under-cowl fuel lines.

Don't forget to run that motor on a motor flusher or in a test tank - you'll fry your water pump impeller in a hearbeat.

Good luck!