View Full Version : Running hot 50 omc

dale johnson
05-18-2004, 11:41 AM
" i have 1988 four winns with 5.0 omc changed t-stat and impellar on out drive runs hot at idle ,once above 1100 rpm starts to cool down. "

05-18-2004, 04:52 PM

05-18-2004, 05:29 PM
" You need to ensure that you have water pumping at idle. To do that, disconnect the water supply hose from the t-stat housing. With boat in the water, start the engine and see if water flows freely. It should be a constant flow. If it does not, backflush that line with the impeller housing removed. You may have pieces of the old impeller or other obstruction stuck in the line.
Also, did you have this problem before replacing the t-stat?
Good luck,
CJ "

05-15-2006, 11:03 AM
You could also have an obstruction in the lower unit on the suction side of the pump. If the impeller housing wasn't installed properly it may be sucking air or the ports may be partially blocked.

05-15-2006, 11:43 AM
"An exhust blockage building backpressure would not be better at high rpm, nor would a blockage in on the sucksion side or the prssure side from pump to thermostat. However a bad circulatin pump or faulty installed thermostat may cause such a symptom.
Check the termostat housing and the water passages again, that the thermostat is properly installed and seated with the lock ring. Check that the v-belt is tight, if everything is ok You may be in need of a new circulation pump."