Logo
FULL SITE MENU

1984 25hp running on one cylinder

H

HOSER762

New member
I'm stumped. I have a 267H4E that has been pretty good to me but it sat the last year or two and this year, it only wants to run on the top cylinder. New plugs didn't help. Both coils check good. I confirmed both cylinders are firing at the correct time via timing light and mark on flywheel. I have good and equal compression on both cylinders. No matter what I did, I couldn't get the bottom cylinder to join in. It looks like it fires judging from the presence of spark. If I pull the plug wire it it bites me but has no effect on the motor. At one point, in desperation, I swapped coils top to bottom and the problem moved to other cylinder. Eureka! Its the coil. Nope. Sometimes, and only sometimes, if I disable the top cylinder the bottom one will run. I now have 3 coils that work on the top cylinder but not the bottom. I've tried them in every combination. When I slowly pull the wire off the lower spark plug, I can hear the spark jumping to the plug inside the boot. Everything tells me the spark is there but the cylinder isn't firing. What on earth is going on here? Any thoughts?

Mark S.
 
I found it. Water in the lower cylinder. That explains how it can have spark but no explosion. I pulled the head and water ran out. Head and gasket look OK. I pulled the exhaust cover and found silicone on the gaskets (somebody got here before me) but nothing obviously wrong. I don't see/feel any cylinder wall cracks. I will replace gaskets and see what that does.
 
HOSER762 said:
I found it. Water in the lower cylinder. That explains how it can have spark but no explosion. I pulled the head and water ran out. Head and gasket look OK. I pulled the exhaust cover and found silicone on the gaskets (somebody got here before me) but nothing obviously wrong. I don't see/feel any cylinder wall cracks. I will replace gaskets and see what that does.
Click to expand...
racerone said:
Check fuel pump diaphragm.-----Check reed valves.
Click to expand...
Did check reeds. All good there. Fuel pump runs off the good cylinder.
 
Saw the exhaust cover/sillycone. If the motors got any amount of time running and been in salt water the mating surfaces can deteriorate and not seal well. In some cases it's so bad it never seals right.
I found taking it to a machine shop and getting the surfaces cut down really made a difference and getting the right gasket is important.
Some cheapo aftermarket gaskets are thin and won't seal right.
Good luck.
 
Back
Top