Running on 2 then 3 cylinders

[fki700]

Hello,
I have a 77 Johnson 70hp I have a problem with it runnuing on 2 cylinders when first started. I idle around the lake for 10 minutes while I am doing this it seems to catch fire on the third ( like hit and miss ) then all of a sudden I am up and running fine with no issues until I park and sit for a while then it happens again. I have gone through all of the carbs cleaned first then went a ahead and rebuilt them with new rebuild kits. No such luck all carbs are in sync and do not know where to go from here any info would be a great help Thank you

 

[archcycle]

Re: Running on 2 then 3 cylinders

Go buy a spark tester and a compression tester. Cheap at any auto store. Test both, with spark jumping a 3/8 gap, and post results from both here. Get a pack of grounding wires with alligator clips on each end from Radio Shack (or just make some) to ground the spark plug wires to the block while you're doing the compression test.

Since it seems to start working fine after warming up, bring the spark tester with you next time you go out and test it again when it's both running badly and running well.

And as for the fuel, have you tried pumping the primer bulb while it's not running well? It could just be getting poor fuel pressure TO the carbs.

 

[jbjennings]

Re: Running on 2 then 3 cylinders

Good advice above,
You might also try switching coils and see if the problem follows the coil.
Good luck,
JBJ

 

[boobie]

Re: Running on 2 then 3 cylinders

You can also use an inductive timing lite. Hook it up to each cyl when acting up, look into the lite and when you see blank spots, that's the cyl that's acting up.