90 HP 2004 Mercury loss of power

[bmoresi]

After sitting for the winter the boat ran fine first time out. Then it started to die while moving under power. Added solvent to removeany moisture, now motor usually runs without dieing but will not go faster than 4200 rpms versus 5000-5500. I have added new gas but still won't go any faster. It is running a good 10 MPH slower than it should at full throttle.

 

[Jacket4life]

Re: 90 HP 2004 Mercury loss of power

Have you ever replaced the plugs in it? Very similar to the problems we had with our 40 HP Merc 4-5 yrs into owning it. New plugs, ran like a champ. You should read around here about plugs, wide variety of opinions. We used the NGK's.

 

[bmoresi]

Re: 90 HP 2004 Mercury loss of power

Thanks I will give it a try.

 

[shankforce]

Re: 90 HP 2004 Mercury loss of power

I would do a complete visual on the motor hood off. Definately check the ignition coils look for coroaded wires or loose wires and check all the wires on your batteries exp the grounds.

 

[bmoresi]

Re: 90 HP 2004 Mercury loss of power

chnaged plugs and it is running just like new. Thank you Jacket I really appreciate the advise.

 

[Jacket4life]

Re: 90 HP 2004 Mercury loss of power

No problem! First time I've helped someone on here, feels good!

What plugs did you use? J/C.

IDK what you mean by 'solvent', but I swear by (and a lot of ppl on here also like) Sea Foam. That stuff is a tune up in a can. I run a can though mine at least once a yr. I go by the can directions, they call for an ounce a gallon. Gas is one of the BIGGEST culprits in OB motor problems. If it's ethanol (which I avoid like the plague!) you shouldn't use it after more than 60 days according to Merc. The alcohol starts to seperate out, and it can cause serious problems. I NEVER keep gas from season to season. At the end of the year, I burn what I have left in lawnmowers, trimmers, etc.

 

[Jacket4life]

Re: 90 HP 2004 Mercury loss of power

BTW-
The advice shankforce gave you is sound for beginning the season no matter what motor you have or how old it is. Lots of problems early in the year for ppl revolve around battery and wiring, ESPECIALLY ground wires.