Logo
FULL SITE MENU

2004 90 hp Mercury running problems

B

bockerman

New member
2004 90hp Mercury 2 stroke – When I give it throttle, it wants to die. I have to move the throttle several times back and forth quickly to get it up out of the hole. Also, after running wide open for several minutes it loses power. It has a mind of its own. It jumps around from 5000 rpms down to 2000 rpms. I have brought the motor in twice to the same repair shop and they say nothing is wrong. They have changed fuel filters – but it still doesn’t run right.
 
I have to move the throttle several times back and forth quickly to get it up out of the hole.
Click to expand...
Check the operation of the accellerator pump.
Also, after running wide open for several minutes it loses power.
Click to expand...
Do you mean the RPM drop but it still runs?
It jumps around from 5000 rpms down to 2000 rpms.
Click to expand...
So the tach jumps all over but does the engine power change? You could try disconnecting the tach to see if it doesn't lose power at WOT.
 
Thanks for your reply.
To answer the second questions; it loses power – meaning that the tach is working, it just indicates what the engine is doing. In other words, I could be traveling at 40mph and suddenly in drops to 20mph for no reason, and then jumps back up to 40mph without touching the throttle.
 
Hook a timing light to #1 cylinder and run the motor.----------Observe the flashing of the light when motor drops RPM.--------If flashing is continuous then hook up to #2 and repeat the test.--Followed by a test on # 3.--------You have of course replaced the water pump impeller recently or is it still the factory original??
 
You should be installing a new impeller about every 5 years !---------When some motors run hot they go into a failsafe mode to prevent engine damage,-------Motor is slowed down using a signal to the powerpack.--------By hooking up a timing light you can maybe find your answers.
 
When some motors run hot they go into a failsafe mode to prevent engine damage,----Motor is slowed down using a signal to the powerpack.
Click to expand...
Excellent diagnosis racerone!

My Merc. factory manual states "every 3 years". Five is pushing it to the limit.
 
why wouldn't my alarm sound if it was over heating?
Click to expand...
Not working? Ground the tan w/blue stripe wire on the engine. Follow the wire from the temp. alarm switch next to the top spark plug. It connects to the wire harness w/a bullet connector. Ground the wire there and it should set of the alarm horn. If not then either the alarm horn is caput, the horn is not getting 12 vdc or the tan/blue stripe wire circuit is open.
 
Back
Top