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1976 35HP Johnson Seahorse (35EL76G) motor won't idle

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Gary35J

New member
I forgot to winterize my 35HP Johnson motor 2 years ago and last year it wouldn't start. This year I cleaned the carburetor, replaced the carb. gaskets with a kit online (didn't replace float though because I wasn't sure how to adjust the new one), replaced gas/oil (added Seafoam), and replaced spark plugs. The engine now starts, but won't idle. I have to keep it revved up a bit and shift into gear or it will die. Tried adjusting the Lean/Rich screw, but it appears to have no effect (didn't hear change in engine speed unless I screwed it all the way in and then it died). I've never worked on a boat motor before (this is my first boat) so I don't know where to go from here. Any suggestions?
 
You know the idle mixture screw is working since it dies when you screw it in. So that is not the problem. Start with a compression check and a spark check. Has the motor ever been overheated? Many '76's have been. Look for discolored paint on the cylinder head.
 
fdrgator said:
You know the idle mixture screw is working since it dies when you screw it in. So that is not the problem. Start with a compression check and a spark check. Has the motor ever been overheated? Many '76's have been. Look for discolored paint on the cylinder head.
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Thanks for replying to my post. The spark is good and the compression on both plugs is 110-115. I didn't see any unusual discoloration around the plugs.
 
Maybe I missed cleaning a fuel jet on the carb? And maybe I should replace the float and see if that helps? Do you know what the float adjustment is for that engine? I was going to go with as close to flush (w/gasket on) as possible, and go with 28-41mm adjustment for the maximum with the float open. Does that sound about right?
 
Sounds like it might be running on one cylinder.----Remove flywheel.----Clean and set breaker points.----Did you clean the high speed jet ( fixed orifice ) that is screwed horizontally into the carburetor bowl , yes or no ?
 
racerone said:
Sounds like it might be running on one cylinder.----Remove flywheel.----Clean and set breaker points.----Did you clean the high speed jet ( fixed orifice ) that is screwed horizontally into the carburetor bowl , yes or no ?
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I'm curious why you think it's running on one cylinder? As I mentioned earlier, I know nothing about engines so I'm trying to understand...please forgive any dumb questions I might ask. If both plugs have spark and both have about 115psi compression, could it still be running on 1 cylinder? I didn't look closely at the actual spark, I just confirmed each plug was sparking. Unfortunately I don't have the manual for my motor (was hoping this was an easy fix and I didn't have to get one), so not sure how to set the breaker points. I found a video on line that talked about high point cams and .20 clearance, but it wasn't my exact motor. Will I need to set the timing if I adjust the breaker points? As to the carb jet question, I sprayed (w/carb cleaner, then blew out with canned air) every hole I could find that wasn't a mounting hole...but I didn't use any wire brushes or special tools/wires to clean the jets...do I need to run something through them?
 
Go ahead and clean the carburetor again if that is what you want to do. But I'll bet it won't do any good. Most carburetor trouble isn't. Checking spark by laying the plugs on the head is a waste of time. You need an open air spark test to be meaningful. Even that doesn't say the plugs are firing under compression. A better test to see if it is running on both is remove and ground one plug wire and see how it runs. Then do the same with the other one. If one makes no difference, that one is not firing the cylinder. There also are other reasons for running on one or poor idle. A leaking fuel pump diaphragm comes to mind.
 
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