Overheating problem

[Robj]

I just took my project boat out on the water for the first time, after 8 months of working on it. It is a Volvo AQ131 with fresh water cooling. When I ran it on the muffs, it ran at about 175 degrees, but today out on the lake it ran at about 200, maybe even as high as 210. Ran great but a little too warm for my liking. I did replace the impeller but it may have been damaged due to a no cooling water incident where it ran for about 10 seconds without raw water. Will change it tomorrow, but was wondering what else could be causing the problem? The thermostat is new, anti-freeze is full. Could this be a manifold problem? When running it on muffs, the entire manifold remains cool, however out on the lake it is warmer especially at #4 cylinder, I know this is a raw water flow problem. How can I tell if the manifold is plugged and not allowing adequate water flow through? I am on holidays and want to get this back on the water tommorrow. Any opinions are always appreciated.

Thanx for your help and have a great day,

Rob.

 

[spoticus02]

Re: Overheating problem

Just ran into close to this problem with my Merc 470, and yes, my impeller was bad. But... while I had the stern drive apart, I simply shoved a hose up to the copper tube that heads up and out to the heat exchanger and pressured up. Water came out full pressure from my exhaust ports, so at least I knew I had great flow through the exchanger. If you don't get good flow, and if your water pump was ever neglected, pieces of the impeller may have broken off and are clogging the raw water side either in an elbow or the exchanger. Installed new impeller, water pump kit, and running soooo cool. You should also have good flow on the muffs out of at least one of the exhaust ports and out the prop exhaust. Not an expert by any means, but just went through this whole procedure, along with an upper stern drive replacement. Good luck!

SP

 

[Robj]

Re: Overheating problem

It ran great on the muffs, nice and cool. Once in the lake she got a little warm. I am picking up a new raw water pump today. Was wondering how I can tell if my manifold is OK. We are on holidays and want to get this fixed so we can get back out on the lake. Any other suggestions are greatly appreciated.

Have a great day,

Rob.

 

[Robj]

Re: Overheating problem

Anyone have any other suggestions?

Thanx

Rob.