485 Mercruiser over heating.

[Landon]

I have two 485 mercruisers in my 1980 wellcraft nova 250. My one engine starts overheating after about 3-5 minutes of running it (goes up over 200f). If you run it faster the temperature goes down a bit. I have replaced the impeller (it was completely burn out), removed the thermostat, flushed the cooling system and changed the coolant, and it still over heats. Im not sure what could be causing this any help would be appreatied

 

[HT32BSX115]

Re: 485 Mercruiser over heating.

I have two 485 mercruisers in my 1980 wellcraft nova 250. My one engine starts overheating after about 3-5 minutes of running it (goes up over 200f). If you run it faster the temperature goes down a bit. I have replaced the impeller (it was completely burn out), removed the thermostat, flushed the cooling system and changed the coolant, and it still over heats. Im not sure what could be causing this any help would be appreatied

Howdy,

Welcome aboard.

It sounds like the impeller failures may have send fragments into the heat exchanger..... restricting raw water flow through it.

Your riser and manifold may be running hot too.

 

[Landon]

Re: 485 Mercruiser over heating.

Howdy,

Welcome aboard.

It sounds like the impeller failures may have send fragments into the heat exchanger..... restricting raw water flow through it.

Your riser and manifold may be running hot too.

Thanks for your help

 

[stonyloam]

Re: 485 Mercruiser over heating.

Look for impeller pieces under the front cap of the exchanger.

 

[Landon]

Re: 485 Mercruiser over heating.

Look for impeller pieces under the front cap of the exchanger.

That's probably it, the impeller was missing chunks when I pulled it out.