2.5L 4 Cyl I/O Mercruiser Cooling Problem

magnogreato

Recruit
Joined
Dec 2, 2006
Messages
3
I have a '89 16' Thunder Craft Classic 2.5L Alpha One 4 cylinder inline Mercruiser I/O and runs fine in driveway...problem is when I connect the muff for cooling I'm getting no water out of the exhaust (?) port telling me that I might have a clogged cooling system? Maybe? I don't know. I do know that some water is getting partially thru because I have a small, slow leak at keel tube under the motor. The temp goes up to 120 slowly then obviously jumps to 160 and climbs and I shut it down after about a minute or two...anyone have any thoughts on this. Caveat....boat has been out of water and in my driveway for two years but engine runs fine, but that doesn't solve my problem. No water out in Neutral or Drive...I was wondering if I shoved a small diameter water hose up the exhaust and tried to unblock whatever might be stopping the output of water if that would help? Any ideas or Help would be appreciated and thanks!
 

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Chances are the impeller in the outdrive water pump is shot. When was it last changed?
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
OK good. From the wording it sounded like you had it running in the driveway and then connected muffs. My guess would be the impeller is shot. An easy way to test is to take the hose that comes from the impeller off the thermostat housing and see if water comes out when the engine is running. Don't do it for too long it is just a quick test.
 
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