4 hp mercury over heating

[loco50]

i have a 1996 4 hp mercury. replaced impeller. spits good water. but overheats after 15 min of run time. previous owner most likely overheated engine by running with shot impeller. water streams out well but steams up after a while. engine has no thermostate. what can i do to fix. its a 2 stroke

 

[oldman570]

Re: 4 hp mercury over heating

Could be that a part of the old impeller is still in the water tube or jacket on the motor and is blocking the water flow after water pressure has built up. You can take the LU off and using a air compresser or water pressure see if the part will be blown out of the motor. Air blown into the tell tail is the easyest way to do the job. Other wise you will need to take the head cover off and see if you can find the blockage or a bad head gasket. If the carb is set to lean it will cause the motor to overheat also. This should be checked also.JMO
Oldman570

 

[loco50]

Re: 4 hp mercury over heating

Thanks will do.

 

[quicktach]

Re: 4 hp mercury over heating

Impeller replaced with vanes in wrong direction ? Did you correctly put the key for the impeller into the shaft when the impeller was replaced ? Or somewhere there's a restriction - water intake fouled with weeds or crud? Check your oil/gas mix 50:1 ? Correct outboard oil ? Check to see if thermostat is fully opening to let water through. Carb set too lean will cause problem too. Correct sparkplugs?

 

[loco50]

Re: 4 hp mercury over heating

I dropped the foot again and looked at the impeller and found a small rubber piece blocking a port. Removed it. Adjusted the lean screw and it runs good. Thanks