454 mercruiser over-heating .. Help!!!

IGUANABOB

Recruit
Joined
Apr 30, 2013
Messages
1
Rebuilt 1974 Mercruiser 454. (200 hours) 350 HP. Closed system - Overheating underway.
This is my SB eng, running 180 degrees and blowing some steam under load, but does fine at the dock..
Port side (same type eng) runs 160 degrees all day long...
I have replaced: Raw water inlet pump & spider, had heat exchanger cored/repaired, replaced BOTH risers/exhaust manifolds, elbows, replaced thermostat (160 degree), installed rebuilt circulating pump. Cleaned strainer basket, cleaned raw water inlet exchanger. No water showing up in the oil pan. It is NOT losing antifreeze (level holding in heat exchanger)..
I am absolutely at wits end on this... Maybe a head gasket leak? Anybody got ANY ideas???
 

Lyle29464

Lieutenant
Joined
Mar 10, 2009
Messages
1,261
Re: 454 mercruiser over-heating .. Help!!!

First guess. Did you buy a marine circulating pump? The auto pump will not work backwards.

2. Local auto store may loan you the testers to check for block, head, or leaking gaskets.
 
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