170 mercruiser overheating

G

gumsfamily

Cadet
Joined
Jul 31, 2011
Messages
6
I have a 1985 four winns freedom 170 I/O with a mercruiser 170 and having overheating problems. Hold good temp for 30 min. then overheats. At fast and slow speeds... I have replaced the impellar, thermostat, exhaust bellows and flushed heat exchanger. I am at a loss of what to do next. There is a small drip from water pump weep hole. Heat exchanger stays cool but engine will overheat. Any and all suggestions will be appreciated.
 
S

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: 170 mercruiser overheating

The leak from the weep hole indicates you need new waterpump cam seals, read this: http://www.sterndrives.com/470_coolant_leak.html Don't worry about the expensive tools they list, don't need them. If your exchanger is cool, but the engine overheats, it sounds like your engine circulating pump is not circulating enough water. The seawater tubes are internal in the exchanger and the coolant flows around the outside, so for some reason that coolant is not being circulated fast enough through the engine. Here is a link to the manual, check the coolant system troubleshooting section : http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html Good luck.
 
G

gumsfamily

Cadet
Joined
Jul 31, 2011
Messages
6
Re: 170 mercruiser overheating

I pulled the cover off with hose attached and ran engine, it appears as if water pump is ok? Also, hooked up clear hose to pump intake hose and looks as if water is moving,just not sure how fast it should be flowing?
 
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