# Need Help Johnson 15



## Brett (Jul 16, 2008)

Anytime an electrical component or it's potted connecting wires
show corrosion or heat damage, I replace them.
Not worth the risk, in my mind, of what you just went through.
Are you sure your block didn't overheat as well?
I ask as your coils showed heat damage at the mounts also.


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## Dadvocate (Jun 26, 2011)

All wires and connectors and bolts were tight and corrosion free that I could find before the trip. I believe it overheated but I'm not sure why? It had a good pump flow at the dock. The plugs are firing but I'm not sure if the spark is hot enought according to the Clymers manual as well being able to only jump a 1/4" gap. I am going to check the compression tommorrow.


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## Frank_Sebastian (Oct 15, 2007)

I would check the thermostat. I suppose there is only one. Also an open charging circuit can burn up the rectifier and cause damage to other components. I don't think that happened on so small and engine.

If it were mine I would take it to a good OMC mechanic if I knew he was trustworthy.

Best regards,
Frank_S


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## Dadvocate (Jun 26, 2011)

Checked the compression. Top cylinder 30# Bottom cylinder 70#. That was giving it 4 aggressive pulls per cylinder. I guess that is a good reason why it died and does not want to start. Oh well back to the drawing board.


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## Frank_Sebastian (Oct 15, 2007)

I would check the thermostat. I suppose there is only one. Also an open charging circuit can burn up the rectifier and cause damage to other components. I don't think that happened on so small and engine.

If it were mine I would take it to a good OMC mechanic if I knew he was trustworthy.

Best regards,
Frank_S


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## AfterHours2 (Aug 2, 2010)

30# and 70# is not good. Might as well either plan on tearing down to examine the extent of damage to cylinders or just sell for parts... If your handy then it shouldnt be a great deal of $$, however, a complete shop rebuild would probably be not as practical for a smaller motor... Good luck.


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## Dadvocate (Jun 26, 2011)

It doesn't sound like you need a ton of special tools. I think I might try it. If it just needs rings, seals, gaskets and a honing it would be worth it. Oh yeah and a new thermostat. Thanks for the replies.


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## Dadvocate (Jun 26, 2011)

Had to work a 48 at the fire Station but I tore into the motor this afternoon. Head bolts were a little loose .Took the head off and found corrosion in the top water jacket but head gasket did not look like it was leaking. No thermostat and corrosion down that passage way. Cylinder look good no scrapes and rings and pistons look good from port inspection plate. I am going to tear into the block tommorow. The upper thrust mount were shot like I thought. My question is is it easy to tell if the rod and crank bearing assemblies are ok?


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## Brett (Jul 16, 2008)

I hate typing... 

http://smallengineinformation.com/?page_id=492


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## cutrunner (Jun 8, 2010)

If the rings and cylinders are good, a bad compression reading could come from bad reeds! Check the reeds before your tear any farther!


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## mmjamp (Jul 3, 2011)

Just a thought, never seen a bad bearing cause low compression. If both cyc. are low first thing I would check is my gauge to make sure you were getting a good reading. Also if the rings, and cyc walls look good on an OMC product head gasket would be my 1st guess, however since you said that looks good, How much play is in the Piston when you try to move it around?


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## Dadvocate (Jun 26, 2011)

Piston has side to side movement at bearings on crank and wrist pin but does not feel like there is play pushing or pulling against crank or wrist pin. Upper cylinder had a lot of caked residue in water jacket around piston. Compression guage pumped up to 30psi on top and 70psi on bottom, triple checked. Reed valves look good and acivated with compressed air as I cleaned them. Head was a full turn loose on all bolts before tear down.Parts should arrive by weekend. Does anyone know what gap should be on wrings if inserted in standard bore or if this is something I should worry about.


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## Dadvocate (Jun 26, 2011)

Replaced rings, seals, thermostat and all new gaskets. Motor fired up 2nd pull. Pissing a good stream motor sounds good just smoking alot due to 25:1 ratio. Plan to run another hour in barrel then head to the lake for varying RPM's til this 5 gal. tank is empty. When will the rings be seated enough to check compression? Thanks to everyone  that posted and to all the good information shared on other posts.


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