1999 50hrp Johnson that has lost power, won’t idle and is backfiring

[flmike02]

I have a 1999 50hrp Johnson that has lost power, won’t idle and is backfiring after several cranks when I attempt to start it. The loss in power happened rather quickly as I slowed to make a turn and then after I opened the throttle back up, it lost half its power. Then after stopping for a half hour, I struggled to start it and it was only running at ¼ of its power at wide open. Now as I struggle to start it out of the water, it backfires every so often.<br /><br />I ordered the manual but does anyone have any suggestions what it could be. I was thinking that it might be a timing issue or a carburetor issue.<br /><br />Any suggestion would be great so I know what to look at when I get the manual.

 

[jegervais]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

What are the compression numbers for each cylinder?<br /><br />It does sounds like it could be a timing issue. 2 things come to mind - <br /><br />-a sheared flywheel key and<br />-a spun sensor magnet <br /><br />Removal of the flywheel is required to chk both of these.<br /><br />-John

 

[Walker]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

Or a fried piston.

 

[flmike02]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

Well I don't want it to be a fried piston!<br /><br />I have not checked the pressure yet but I will once I get my manual. I plan to go over just about everything.<br /><br />Thank for the suggestions so far!

 

[rodbolt]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

before ya get to crazy with flywheels and such test the compression, if its good test the spark, if the key is sheared it will still spark just out of time, if the magnet is loose it will usually spark just out of time, if it only sparks on one cyl carefully inspect the powerpack wiring at the lower stbd edge of the head, its routed past a sharp edge and tends to chafe the wires through and short the charge coils to ground.<br /> a quick way to check for a sheared key is remove the plugs, insert a small phillips screwdriver in the cyl,roll the flywhell gently by hand clockwise until you feel the #1 (top) piston at tdc. once you find TDC rock the flywheel back and forth to get a feel of no piston motion, the timing pointer should now be within a degree or two of the TDC mark on the flywheel. when you turn the key on,no start, do you hear the alarm horn self test ?

 

[tashasdaddy]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

great point rodbolt.

 

[flmike02]

Re: 1999 50hrp Johnson that has lost power, won’t idle and is backfiring

rbbolt<br /><br />Thanks for that info. I will try those tests and yes the alarm horn does go off when I turn the key.