half speed under load

[amplex]

i have a 9.8 hp merc thunder bolt s/n 7084063 that runs fine in the tank but when it's put back on the boat and driven under load it only runs at 1/2 or 1/3 speed with the throttle twisted full.<br /><br />i'm not sure what year the motor is. <br /><br />i presently don't have a manual to refer to and i would like to check the timing components also.<br /><br />any help would be greatly appreciated

 

[JB]

Re: half speed under load

Howdy, Amplex.<br /><br />Timing isn't your problem. You are probably running on one cylinder.<br /><br />Don't be fooled by how it sounds with no load.<br /><br />Pull or short out each plug while running. If it dies, that cylinder is good. If there is no change the cylinder is not making power.<br /><br />If you can get spark for that cylinder, check reeds and compression.<br /><br />Let us know what you find.<br /><br />Good luck.

 

[RWC]

Re: half speed under load

Amplex,<br />That is exactly what my 5.5 Evenrude was doing.<br />I had checked the fire in the top plug but not the bottom. I didn't know they have two sets of points , coils etc. I had no fire to the bottom cylinder. I replaced the bad coil and it ran fine. That was after I removed the carb. and cleaned it and it still woundn't run under load. It would idle in the barrel. Your problem sounds identical to mine.