running hot

[rlp]

i am runnin a 91 350 i/o .it started heating up a <br />low rpms but would cool down as the rpm picked up.<br />i figured water pump or thermostat so i replaced both.now the temp gauge dosent read hot but jumps<br />up and down at 150%.i can hear water boiling in the manifolds.all water passages appear to be clear on the hose.do i need to prime the new pump?<br />any ideas

 

[sea wolf]

Re: running hot

check lower unit impeller.

 

[oldboat1]

Re: running hot

An air pocket in my closed system provides similar symtoms -- could be the problem in your case (?) Also, it's probably a good time to check the wiring for the gauge. You might clean and reconnect the connection at the sender, the gauge and the ground connection.

 

[record hunter]

Re: running hot

I agree that it could be your impeller. Did you put the thermostat back in the right spot .I know on my mercruiser it goes on the top of therm housing. Change your temp sending unit its cheap