over heating at idol speed

[Beachin centurion 0]

Hey guys,

Finally got the 1982 ski centurion in the water for the first time this year; however, I am having issues of over heating at idol speed only. I replaced the impeller, but still had the same issues at idol speed only. Next I removed the thermostat (just to get through the weekend) but still no luck. I am looking for some ideas of what else might be causing this issue...any thoughts or suggestions?

 

[Skibumm 184]

That age it could be hoses that have collapsed or even clogging of the freshwater intake. I will say it sounds like impeller to me. It's quick to check to make sure. Also make sure that your pump is turning. Did you replace just the impeller? Do you have a plastic housing or the metal hosing that came with the boat. if it is plastic I would change the whole pump out not just the impeller as the plastic and grove or even get misshaped. Check it out on a hose to see if it stays cool and runs water through it. IF so you have a pump issue most likely. IF it still gets hot it would indicate a blockage somewhere.

[Beachin centurion 0]

I replaced the impeller, and it has the original shorwood metal housing. My next step was going to check out the raw water strainer and check for additional blockages. This past weekend was the first time the boat has been in the water in three years. I had the boat hooked to a fake lake about a month ago while performing a tune up, the temperature never got above 100, but it didn't run very long due to some carb issues. This past weekend while removing the thermostat I disconnected the hose from the pump,started the boat and water(hot) came out of the pump hose instantly.

[Beachin centurion 0]

A crushing speed the temperature drops automatically to normal operating temperature (160) and even lower once I removed the thermostat. Just wanted to throw that out there

[surf moocher 127]

That age it could be hoses that have collapsed or even clogging of the freshwater intake. I will say it sounds like impeller to me. It's quick to check to make sure. Also make sure that your pump is turning. Did you replace just the impeller? Do you have a plastic housing or the metal hosing that came with the boat. if it is plastic I would change the whole pump out not just the impeller as the plastic and grove or even get misshaped. Check it out on a hose to see if it stays cool and runs water through it. IF so you have a pump issue most likely. IF it still gets hot it would indicate a blockage somewhere.

 

I think I've heard of others having issues with the impeller not turning or not turning consistently due to grooves on the inside of the face plate that seals the impeller inside the water pump housing, I wonder if there isn't enough pressure to turn the impeller against resistance of grooves at lower rpm?

[DaveB 5]

The grooves actually allow the water to bypass around the the impeller so it doesn't pump properly once you speed up ( raise your rpm ) there is enough force to pump the water and your temp drops. Take off the pump and belt sand the brass plate , re-assemble and everything should be golden.

[Skibumm 184]

The grooves actually allow the water to bypass around the the impeller so it doesn't pump properly once you speed up ( raise your rpm ) there is enough force to pump the water and your temp drops. Take off the pump and belt sand the brass plate , re-assemble and everything should be golden.

Exactly this. Also do not get rid of the metal pump housing. I wish I still had mine but the plastic ones you replace the whole unit now. I think for your pump you can actually buy a new brass plate for it. I know a few years ago you could purchase everything in the pump and keep the housing.

[Beachin centurion 0]

Hey guys thanks for all of the advice!!! I'll probably be able to check this out next week,I'll definitely keep you guys informed!! Thanks again

[TexP51 6]

Check and make sure your belt is very tight.  Later models have a single serpentine accessory drive belt, but your ‘82 I think had v belts.  If they get wet they slip if not really tight.  Other idea is the engine driven water pump could be a problem.  Is water actually circulating through your block?  The impeller most of us are talking about pulls lake water and provides it to the open cooling system, but the Chevy small block also has a mechanical engine mounted water pump that circulates the water in the engine cooling circuit.  If either pump goes down you overheat.  

[jtryon 24]

this topic is 5 years old