Need Help Johnson 15

Discussion in 'Outboard Maintenance' started by Dadvocate, Jul 26, 2011.

  1. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    1984 Johnson 15ECRM (manual, electric start)  Motor sat for approx 4 years. Rebuilt waterpump, carb, fuel pump and redid some wiring. Motor ran several dozen times on hose and in barrel. Good water stream before and after new impellor. Night before sea trial noticed red wire from rectifior corroded and broken off. Had to strip back all the way to rectifior and splice in a new one. Took boat over to Riverbreeze ran for about 10 minutes on plane (20mph?) 15' Johnsen skiff w/ 2 adults. Motor started slowing down to about 10 mph and then down to about 5 mph and noticed smoke coming from cowling. Smoke dissapated and removed + cable before opening cowling. Motor would pull through manually but not start. Towed back and checked when I got back home and noticed several heat related problems. 1 wire from power pack to coil melted through heat shield and insulation and probably grounding out. Both coils show melting where the attach to block. All 3 coil mounting bolts loose ( all where tightened recently). Checked for spark with tester built using SSCHAPTERPSA website. Spark will only jump 1/4" inch not 1/2" described on that website. Shot premix straight into carb with no result. Don't have much experience with outboards but have researched many forums. What should I try next?
     
  2. Brett

    Brett > PRO STAFF <

    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.
     

  3. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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.
     
  4. Frank_Sebastian

    Frank_Sebastian Well-Known Member

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    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
     
  5. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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.
     
  6. Frank_Sebastian

    Frank_Sebastian Well-Known Member

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    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
     
  7. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    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.
     
  8. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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.
     
  9. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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?
     
  10. Brett

    Brett > PRO STAFF <

    I hate typing... ;)

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

    cutrunner Cert. Yamaha technician

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

    mmjamp I Love microskiff.com!

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    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?
     
  13. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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.
     
  14. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    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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