Johnson 9.9 no hitting full revs under load

[Hobie17]

i have a 1992 Johnson 9.9 outboard - runs fine at idle and ran fine for a couple of hours, then after slowing to an idle, giving it full throttle, it would not rev enough to plane the boat (it planed easily prior to this) - rebuilt the carb (found nothing, cleaned it and blew it out with compressed air) - it started fine, throttle opens fully but still not enough revs to plane the boat - any ideas of what i can look at next?

 

[Rick.]

Re: Johnson 9.9 no hitting full revs under load

Use a spark gap tester and check to see you have good spark on both plugs. Spark should jump 3/8 inch and be blue/white and snappy. These motors run very smooth on one cylinder and especially if they aren't under load. Under load they just don't have the power (by 50%) that they should. Give that a try and let us know. You may find it works well when cold and fails as the engine warms up so test for spark while it is acting up. Best of luck. Rick.

 

[Hobie17]

Re: Johnson 9.9 no hitting full revs under load

thanks Rick! for both the very quick response and perfect diagnosis!, it is unbelievable how smooth it runs on one cylinder - we took it out last night - it ran fine for about 30 mins., we shut it down for about 20 mins.....it started right up but with 50% power, i pulled one plug wire, nothing happened, it ran the same - replaced the wire and pulled the other one....the engine shutdown.....so i'm assuming its the power pack for that cylinder....thanks again and happy boating!

 

[Daviet]

Re: Johnson 9.9 no hitting full revs under load

You might want to check the ign system for the defective cylinder, coil,wire,plug.

 

[Rick.]

Re: Johnson 9.9 no hitting full revs under load

I agree with Daviet on this. Power pack would be my last pic. Probably most expensive too. Rick.

 

[Hobie17]

Re: Johnson 9.9 no hitting full revs under load

sorry - my error in calling it a power pak - in reality it was the coil i was looking at - replaced the coil for that cylinder and it now runs perfect - thanks again for all your assistance - it's greatly appreciated!

 

[Rick.]

Re: Johnson 9.9 no hitting full revs under load

Yahoo! Another Evinrude is back on the water. Rick.