2000 Merc 90hp - no full power

[RonRaetz]

starts great, idles great. often but not always normal low end. after about 1000 yds at full power (4800 rpm) it drops back to about 3800 and that is all it has. New set of plugs did not help. all 3 plugs are very wet with what looks like oil. Have run motor for 3 years, total of perhaps 20 tanks (12 gal.) of gas. Any guesses? I've been told maybe "spark module

 

[Greg Lawrence]

Re: 2000 Merc 90hp - no full power

have you ever cleaned your carbs in those three years? are you running a water seperator?<br /><br />start with compression, fuel, then spark.

 

[RonRaetz]

Re: 2000 Merc 90hp - no full power

Two fresh tanks of gas did not make any difference, exact same symptoms. I hate to check compression - afraid of what I might find, but it's probably a good next step.

 

[Hooty]

Re: 2000 Merc 90hp - no full power

At what point did you look at the plugs? Was it after trying to run wfo or after you idled in and shut down? The time to chesk the plugs is right after you tried wfo and engine and revs fell back, see if plugs are wet or dry.<br /><br />c/6<br /><br />Hooty

 

[fshng4]

Re: 2000 Merc 90hp - no full power

Just went through a similar problem with a 1994 115hp Yamaha that had a loss of power. Mine turned out to be a bad coil. Did you check your coils for spark?

 

[alounsbury]

Re: 2000 Merc 90hp - no full power

Sounds very electrical in nature. Since all plugs seem wet - will assume that this is not a single plug quittin on you, but rather all three cutting back. That would imply a "possible" stator problem - basically as engine heats up a temporary short in the winding is coming into play and reducing spark voltage.<br /><br />If you are handy with a multimeter, check out http://outboardparts.com/mercury/troubleshooting/troubleshooting11.htm for the correct readings on your motor. Note you should take the readings AFTER the problem occurs.<br /><br />Good luck.