I have a 2002 Merc 90 outboard. When I run at a high rpm and then slow down the motor dies or is slugish. Why?

Question

This problem has happened before so I replaced the fuel filter, water fuel seperator, waterpump and impeller. When it is sluggish if I give more throttle it will die. If I keep the throttle in the same position the rpm slowly increases.

The plugs are also gunked up. Oil injection problem? Throttle problem?

Please help!

Answer 1

dirty carburetors... try pushing your choke when you think it is gonna die out on you... if it keeps it going or corrects it ( though temporarily ) then you have dirty carbs....

Answer 2

More than likely you need to get the carb tuned up.

Answer 3

Check your fuel lines from the filter thru to the tank.  Just a very minor obstruction will cause that.  Sometimes a larger filter will help too.  Sometime the fuel line connector to the tank is sticky too. Change this first.

Answer 4

I sounds to me as if your fuel tank is polluted. It probably needs a good clean.

I have experienced this type of problem, once only before.......... with my first car, bought brand new!........ I'd drive about 5 miles and then, in the same place, driving to work, she would slowly die!

It was spooky!

I'd wait a few minutes and then I could drive another 5 miles and then she would die again!

The long term answer was a fuel tank filter bubble around the fuel pipe.

Answer 5

Is this a 2 stroke or 4 stroke? If its a 2 stroke, did you definitely use the correct injector oil? Sounds like its burning too much oil, causing plugs to gunk up. To rule out a few things, you may want to run a gas line to a temporary fuel tank on board, like a 5 gallon gas tank to see how it runs. A compression check will tell you a lot about how your cyliners are operating. Finally, a dirty carburator or even air intake system can cause poor performance like this.....oh, and choke may be sticking too.

Answer 6

incorrect spark plugs. Check timing.reset idle rpm.fuel contamination. Disconnect oil injector,mix 50/1 (quicksilver oil) in fuel tank. 50/1 is app. 3oz. oil per gal. gasoline.

Answer 7

have your electric fuel injection system checked out and also your oil injection system it may be mixing too rich but if it is not letting enough gas in to compensate with the oil it could be causing your plugs to foul

Answer 8

Start with a basic compression check, could be a minor vacum leak