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1994 Mercrusier 350 Mag ECT bravo closed cooling system

L

Lucky Duck

New member
6/25/24

1994 Mercrusier 350 Mag ECT bravo closed cooling system

runs hot on water hose and in water. Installed new thermostat, still runs hot. Water expelling from stern drive leg (exhaust ports) running extremely hard at idle as compared to when there was no issues. Thinking that water from hose or sea cock pick up is not cooling antifreeze in Heat Exchanger? Some type of blockage????
 
not sure on the sea water strainer? think so. however the engine overheats with the "quick connect hose" (fresh water) as cooling source? does "quick connect" water go through "sea water strainer"? Mot sure on age of impeller? does "quick connect
" fresh water input need the pump?

thanks so much for your thoughts? hope I can resolve the issue. nearest mechanic is 4 1/2 hours away.
 
Personally, I am not aware of a quick connect raw water connector on that vintage engine.. Sea strainers, if installed are before the inlet to the
engine mounted raw water pump.
Raw water impeller... Merc recommends annual replacement. I don't use my boat anywhere that often ( sob,,, :-( ) so I replace it every third season,,,unless I "find" a sandbar not on the charts. Life running dry about 20 seconds... churning sand a no no...
IF no sea strainer, could be crap in the heat exchanger on the inlet side... Depending on construction of heat exchanger, it's easy to undo one bolt and clean out the inlet side and/or two bolts and inlet and outlet sides and clean out the tubes.. A treatment with salt-a-way will often clean out minor salt clogs without disassembly. When running un the water when it gets hot carefully feel the elbows to soo if they are too hot to touch.. IFSO there is a lockage. Of course a piece of old broken impeller could also impede water flow,
 
sandkicker said:
Personally, I am not aware of a quick connect raw water connector on that vintage engine.. Sea strainers, if installed are before the inlet to the
engine mounted raw water pump.
Raw water impeller... Merc recommends annual replacement. I don't use my boat anywhere that often ( sob,,, :-( ) so I replace it every third season,,,unless I "find" a sandbar not on the charts. Life running dry about 20 seconds... churning sand a no no...
IF no sea strainer, could be crap in the heat exchanger on the inlet side... Depending on construction of heat exchanger, it's easy to undo one bolt and clean out the inlet side and/or two bolts and inlet and outlet sides and clean out the tubes.. A treatment with salt-a-way will often clean out minor salt clogs without disassembly. When running un the water when it gets hot carefully feel the elbows to soo if they are too hot to touch.. IFSO there is a lockage. Of course a piece of old broken impeller could also impede water flow,
Click to expand...
6/26/24 Thanks for the reply. There is a "quick connect" raw/fresh water hose type inlet valve on the starboard, rear top of the engine. Given water runs extremely strong out of the stern drive ports when the engine is running on the "quick connect hose, I am thinking the issue is not in the raw water cooling circulation? I am thinking the "circulating pump" for the closed system cooling system for the antifreeze is not working?

However my mechanical skills and knowledge is very limited.
 
Visual observations on water flow aren't accurate...
Are you sure the exhaust Elbows aren't clogged? When were they last replaced??
 
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