1998 Merc 150 Outboard Throttles up on its own???

[Ant-Knee]

Hello All,

I have a 98 merc carberated that runs real strong..

The problem that I am having is that if say im trolling and RPMs are at 2000, the motor after a bit will run up to 2500 RPMS on its own with out me bumping up the throttle.. It does not seem to happen all the time but alot.. What could cause this, I am thinking maybe the fuel pump.. or it's in the fuel system.. I am not to sure.. Another thing that I thought was I could have a bad reed or two.. Any advice is welcome...

Thanks all,

HAppy Boating

Ant...

 

[mudcat6]

Some of the merc's (my 115) start & run on 2 cylinders until reaching app 1800/2000 rpm; then the other cylinders kick in. This is normal; built to do this. When the other cyls kick in, it feels like you just hit turbo... Big increase in rpm's and speed.

 

[wired247]

The air valve on the port side head warms up and opens and leans out the mixture.

 

[Ant-Knee]

Please look at this link below , I took a video and posted a new thread but this is the issue..

http://forums.iboats.com/forum/engi...board-150-midrange-issue-watch-video-plz-help

 

[ondarvr]

I would try putting my hand over each carb to see it it runs better, if it starts to improve it's fuel related, no change and its electrical. I assume the link and sync has been done correctly. Also try advancing the timing manually and then advance the throttle manually, independent of each other, see it it reacts corrrectly with each.