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496 Mag raw water circulationoil temp

W

wilstruck

New member
My 2002 Merc. 496 Mag has an i

My 2002 Merc. 496 Mag has an issue with oil overheating after a long haul (1 hr + running) and dropping oil pressure. Water flow out of port side exhaust significantly less (40% less) then starboard. Riser and exiting water warmer on port side to the touch. Had a new manifold installed on port side when winterized last season. Had marina look at this and they said I had a blockage (Seaweed /Grass) in power steering cooler which they replaced but still have less water flow issue. Overheating oil issue used to occur after 20 min now after 1 hr+. Could this be a worn water pump from blockage or issue with oil cooler? I was told they checked oil cooler and rest of system with no obstructions found. Raw water flows from power steering cooler to oil Cooler to heat exchanger on port side. Continuous alarm sounds till throttle brought back to neutral with significant oil pressure drop according to gauge. Engine temp will maintain 150 degrees. Where should I start looking to correct this problem? Thanks in advance for troubleshooting help.
 
"Could this be a worn wate

"Could this be a worn water pump from blockage..."

Yes. Change the oil to a synthetic. Merc. makes a synthetic 25W40. Mobil 1 15W50 is a good oil to use. Synth. Oil won't break down.
 
is the saying true that if you

is the saying true that if you use conventional oil ans switch to a synthetic you have to stay with a synthetic?
 
"On inspection of impeller no

"On inspection of impeller no broken fins or pcs missing. How tight should impeller be seated in housing? Meaning should I be able to spin pump by hand or should it be fairly tight while trying to spin via the pulley?

Thanks,"
 
Yeah lol sad thing is I had it

Yeah lol sad thing is I had it apart a few weeks ago and going to have to take it apart again! It will be coming apart this weekend but was just curious of fitment!
 
Ok replaced impeller and now h

Ok replaced impeller and now have to throttle up to about 2500 rpm to see water flow from exhaust. Pump feels same as with old impeller. I can still spin pully fairly easy! Guess this means bronze housing worn and needs to be replaced?
 
"ok had pump looked at by mech

"ok had pump looked at by mechanic and said its fine. Replaced impeller and still have same issue with less water from port side. Port side is the side with new manifold. New manifold is cast iorn and starboard is original 2002 cast aluminum. Could this be the reason for diffrent water flow?Could the newer design have different water passages(smaller), causing diffrent flow and temps?

Guy thanks again for all the help thus far."
 
Wil:

Is the port manifold m

Wil:

Is the port manifold made by GLM? The T'stat hsg. may have some crap stuck in it blocking water flow to one of the hoses. Follow all the water hoses from the sea pump w/your hand. Feel for any kinks or flat spots in a hose that could restrict waterflow.
 
"OEM mercruiser manifold. I fo

"OEM mercruiser manifold. I followed all lines and removed and backflushed at all points, coolers, heat exchange etc.....this really has me stumped. I spent all day working on this thing. Even went out an bought the merc flush kit that clamps thru drive to make sure i was getting good water flow for pump to pull a suction. With rebuilt pump installed had to throttle up to 2000 rpm to pull suction and get water flowing. I was told system could have air in it and to put in water and run it. Going to give this a try in the morning and see what happens. I NEED a good marine mechanic in New Jersey."
 
"Have you examined the risers

"Have you examined the risers and elbows? Gaskets on wrong? One boater told of a heat/water flow problem that ended up being caused by mouse nest in the "Y" pipe.
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I removed the port side to che

I removed the port side to check if it was installed wrong but everything looked good. Compared to parts scematic and it all looked correct.
 
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