1985 7.5 HP Merc has severe kicking and often dies at idle speeds.

[kdegru]

I bought this motor used recently but it is super clean with very low hours by all appearances. When I tested for a short run test before I bought it, it seemed to run fine but I could not run it long because there was no water pump output. I did an impeller replacement and now I have good water flow but I have discovered a rather severe kicking that starts shortly after the motor begins to warm up. This is much more pronounced at low idle speeds. I have monitored the two spark plugs with testers to visually assure myself that spark is not missing from either plug when the kicking occurs. Any ideas where to begin troubleshooting this problem? i do not want to put this motor on a boat until I have reliable idle and the motor will not die.

 

[imported_bowfisher]

Re: 1985 7.5 HP Merc has severe kicking and often dies at idle speeds.

Does it quit "kicking" if you pull the choke out?
Sounds like maybe a lean condition.

 

[kdegru]

Re: 1985 7.5 HP Merc has severe kicking and often dies at idle speeds.

Does it quit "kicking" if you pull the choke out?
Sounds like maybe a lean condition.

The kicking seems reduced or no longer happening with maybe 1/2 to 3/4 choke. If I go full choke the motor of course just stalls out. What are the things to check for a lean condition? This motor uses the Wallbro WMB-4 carburetor with a self contained fuel pump.