Overheating 190 Merc

vicsponjr

Petty Officer 2nd Class
Joined
Aug 21, 2004
Messages
174
Hi All<br />I have a 1985 Citation with a 3.7 190hp merc, alpha drive. The boat was sitting a while before I bought it. Last season I had it out and coolant began leaking out of the front cover. I successfully repaired the internal water pump using the cam repair sleeves and new seals. Over the winter I had the bellows replaced and a neutral stall switch installed. I told the mechanic to change the impellers but he said they "looked good".The first time I took it out this season it was running at 175 degrees and started boiling out at the radiator(?) cap. The cap was rusted and falling apart so I replaced it and the thermostat. The mechaic at the Merc dealer said the boat should run at about 150/160 degrees, which it did in the driveway. I noticed that when running in the driveway water was only coming out of one side of the outdrive even though there was holes on both side. I took the boat out yesterday and was running at 175 again. After a while we started putting a load on it and ran it at about 3/4 throttle. The temp went up to 200/225 before we shut it down to let it cool. Coolant boiled over and into the overflow bottle. Also a little seapage at one of the hoses. No oil in the water, or water in the oil. I'm guessing it to be the raw water pump but want to know if there might be something else to check. <br />Thanks in advance!<br />Vic
 

Richard Petersen

Senior Chief Petty Officer
Joined
Dec 17, 2004
Messages
778
Re: Overheating 190 Merc

Older boats have cooling problems due to age of rubber hoses. Check them cold and then when at 3/4 throttle. Could be tired hoses collapsing when hot. Start with the pump suction ones. then check all of them hot. Don't cook the engine.
 
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