Reply To: 1957 johnson 18hp fuel mixture

[Don]

duralark wrote:

Fleetwin, thanks for all the ideas. I’m interested in anything that would allow air to leak into the crankcase enough to prevent fuel/air mixture being drawn from the carb thru the reeds. The carb is not the problem, nor is the ignition (good spark from new coils/points/condensers on both cylinders, nor is compression (65-70 psi on both also).

The damage to the seal at the top of the driveshaft you describe is interesting. It would appear from the parts diagrams that there are no crankshaft seals as such; is this right? Does the seal you mentioned serve as a crank seal? I’m wondering how it could be intended to keep water out of the gearcase, since it’s about a foot above the waterline…? So I guess I’m going to pull the powerhead and see what I see. The shock absorber in the driveshaft is also something I’ve never seen, so this is new territory for me too. Thanks again, and I’ll let you know what I find for sure.

Bob / Duralark

1954 Johnson 5-1/2

1956 Lark 30hp

1958 Lark 35hp

 

Don’t mean to confuse… I wouldn’t waste too much time on the upper slinger or pull the powerhead to check the lower seal components. I really don’t think those items are making the engine hard to start. Again, there is no actual upper seal on this engine. If there was a problem, you would see oil all inside the ignition plate, and you said you have peeked inside.
I would really stick to simple things here. Prime the cylinders with fuel/oil mix, then try to start cold and see what happens. You also mention, perhaps I am mistaken, that the engine runs OK once started and starts OK warm, is this correct? An engine with a crankcase sealing issue is not going to run real well, especially at lower speeds.
Like I said, try priming the cylinders with fuel/oil mix, does it seem to start cold OK when this is done?
If so, then squirt some fuel/oil mix into the carb throat past the venturi and try starting it cold this way, does it start OK doing this?
If so, I would suspect you have a choke issue, or perhaps you are not priming it up enough to fill the carb bowl.
Again, be sure you tank has fresh/uncontaminated 16:1 fuel mix. Perhaps your primer button isn’t working, so you are really not filling the carb bowl. Just cuz there is fuel in the filter glass bowl doesn’t mean there is fuel in the carb bowl.
And again, remember, these engines oftentimes start cold better when the throttle is advanced beyond the start position, especially if the throttle pick up is not set correctly.