Mercruiser 470

"I have an overheating problem

"I have an overheating problem, afyer tracing the flove of all the coolants, there seems to be a blockage in the raw water system between where the hose comes out of the heat exchanger the outdrive. any suggestions?"

"Ayuh,... Take it apart,+

"Ayuh,... Take it apart,+ Flush it...
You may as well change the impeller while it's apart too..."

"Let me list what I have done

"Let me list what I have done
Impeller was changed in June since then it ran for 4 weeks then overheated again.

1)I have removed and checked the thermostat, it works
2)removed all the hoses on both closed and raw water sides of the heat exchanger and flushed both sides with a hose, water runs freely
3)turned engine over with hoses removed and boat in the water, raw water supply runs freely, close side water runs freely
4)connected everything up and started boat overheats in about 17 minutes
5)Pulled boat from water and removed sterndrive(Alpha One) ran water through stern drive, water runs freely
6)Disconnected hose from raw water to Manifold water fills up and slowly seeps out.


Is there anything I can flush that part of the system with that will not damage it?
"

Try a new exhaust elbow

Try a new exhaust elbow

"Removed the exhaust elbow, va

"Removed the exhaust elbow, vacuumed the area under it ran water through both the elbow and the area below and now it seems clear, I am soaking the elbow in a descaler solution made for marine use Rydlime Marine http://www.rydlymemarine.co.uk/ will be putting it all back together toningh and testing it tomorrow. Thanks for the help"

"The engine is now running wel

"The engine is now running well, the only thing is it may be running too cool, two days in a row I ran at 3000 rpms for 40 - 45 minuttes and the temp gauge never went above 150, but at least its not over heating"

"Don't worry; be happy. <[

"Don't worry; be happy. "

"Mine never goes over 140 and

"Mine never goes over 140 and it runs like a top so if that aint broke don't fix it.

Actually I've put over 1000 miles on it this year alone according to my fishfinder, speedometer and never missed a beat."