1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

[Jeffs62]

It's a solid motor. My father in law had some work done on it a few years back ran some bad gas through it and then gave up on it. I got ahold of it. Finally got it started wouldn't hit wot adjusted a screw on the carb and finally got a good sounding motor. Only problem is no matter where I set the throttle it. Seems like it runs slower or faster then before. Some Times it dies out some times it peaks. Also took the fly wheel off cause the keyway dropped out and cleaned everything. I could use a little tuneup literature and a few pointers. I can't find anything except its a 70 4hp. Any help will be great!

 

[Jeffs62]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

Looking to set the points also so any specs, tips, or tricks. Thank you

 

[194269]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

I have 1972 Merc 40 and it has CDI, (no points and cond.) not sure if yours is the same. Sounds like you need to rebuild your fuel pump and carb. Also check to see if the pulse line between the engine and fuel pump is not cracked.

 

[Jeffs62]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

Got the new Impeller in and working great. Checked the fuel lines and all looks. Good. Carbs getting overhauled tomorrow. But I did notice. I'm running the engine in a barrel. That there is alot of fuel/oil accumulating on the surface. The exhaust manifold gasket may be leaking so I'm planning on changing that. Couldn't get a good compression check. Dunno if its my gauge or the difficulty without the pull cord but I was only reading about 30lbs. Plus I have no literature to compare. Also there is a point but I did not notice any condensor. Typically theygo together but I remember wondering why it wasn't there. With it under the flywheel I can't adjust it while it's running using the dwell like my old 62 chevy so if anyone has the. Rule of thumb or a feeler gauge size would be awesome. Thanks for everything I'll post after get done with the carb.

 

[194269]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

If the coil is under the flywheel, then set the points @ .018. If the coil is not under the flywheel, then you have CDI w/points and don't recall what the points are set at. You need to set the points with the flywheel off, and on the high side of the cam.

 

[Jeffs62]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

The coil is mounted on top of the cylinder right above the sparkplug. Its the thunderbolt ignition from what it says. Under the flywheel I have the stator and then next to the shaft in front is where the points are at. I initially took off the flywheel to check why I wasn't getting spark and found the keyway for the flywheel came out and was wedged in my points. So cleaned that up put in a new keyway and she fired up. Just not sure how bad it's off now. What is CDI

 

[Jeffs62]

Re: 1970 merc 40 4hp. Just inherited along with all the problem. Rpms fluctuate

Well carb is rebuilt. New fuel lines just because I was in there. Running alot Better now gonna take it out tonight for a test run. I have noticed that on the carb the fuel filter canister is on top of the float. Right before it gets to the filter there is a little hole on the top of the bowl and it is dripping fuel out. I'm not site if it's supposed to be a vent hole or what but any ideas or help would be great. Thank you