Starboard engine overheating at low RPM

Wildstyle

Would anyone know why that is happening? As soon as I give it throttle on the lake it cools back down and runs fine. But as soon as I go low RPM in the channel, it starts beeping and the gauge says close to 250F degrees. 

Dream_Inn

Sounds like either an impeller or blockage in the water line.

Black_Diamond

+++ on the impeller

rasbury

Yep, impeller more than likely...al what do you think about the ss wear plates and the shorter impellers? Mine worked fine....well assuming I get back in the water..

Wildstyle

Ok thanks for your help guys. I’ll get it apart this week and replace the impellers. I YouTube’d It and it seems like a simple job to do...I say that now of course...

Black_Diamond

Hardin Marine for the SS pumps. Uses std Merc impeller. Wear plates to rebuild. 

Wildstyle

Quick update: the impellers were both changed, but it’s still overheating. They’re going to haul it out and inspect / flush the coolant system I think next. 

Liberty44140

I’d buy the Hardin pump and install before paying for a haul out. Pump will pay for itself in the price of a haul out.

rasbury

@alswagg I have had good results. It looks exactly like the merc impeller...stainless tops and bottoms and I have the brass pump body. Assuming I ever get back in the water...

pistole

If you have a fresh water cooled system, check and clean the heat exchanger. 

Black_Diamond

A new impeller with a worn pump will not solve the problem. Basically if you have any grooves where the impeller sides run it will not move water well enough. 

Wildboating

Did you check the recirculation water pump on the front of the motor?  

earl1z19

A new impeller with a worn housing will actually make the situation worse. The old impeller has the groove already worn in the end to match the worn housing where the new impeller does not.

pistole

Unless the sea water pump's impeller was completely gone, it's unlikely to be the cause of your overheating. 

Check for airlock in cooling system  (easy) , belt tension (easy) , and maybe obstruction in cooling system  (harder)

Wildstyle

pistole said:

Unless the sea water pump's impeller was completely gone, it's unlikely to be the cause of your overheating. 

Check for airlock in cooling system  (easy) , belt tension (easy) , and maybe obstruction in cooling system  (harder)

Yep that’s exactly what it was. It was an airlock...apparently they didn’t tighten the hoses all the way when getting it ready for summer. Tightened them up and problem went away! Whew!

aero3113

Great fix!!