8.2 MAG EC HO Seawater Pump PSI


S

Schatley35

New member
Hello Fellow 496 MAG HO owners,
I have a 2012 350SS and the Port engine always runs around 6~8 psi higher than the STBD, depending on RPM I am running. Port usually is around 20 PSI while the STBD is always around 14~15 PSI. Port Eng temp is solid at 167, STBD always runs hotter around 174-176. Understand the Port engine has the water heater acting as an additional Heat Exchanger, but more concerned with the water PSI. Both seawater pump impellers were changed early Spring (March), both engines have run approx 35~40 hours since. Does this seem normal/acceptable? Bothers me, will check the incoming water hose to ensure no blockage. Anyone have this much of a difference? Thanks

Steve
 
I don't know if you boat in salt water or fresh water. On my 8.2L engines, I found that the Mercruiser Water Pressure sensors were very unreliable. If I would get a season out of them, that was good as a salt water boater who even flushed his engines every time. . And Mercury would never cover these things under warranty---even for those less than 1 year old upon replacement. On the 8.2's, the sensor is located in the back of the engine. I got very adept at replacing those myself. Remember that there is a small plastic cage in the electrical connector to keep the pins aligned. They're easy to drop in the back of your bilge. Good luck.
 
Use an IR temp gun and compare the gauge reads to the IR readings. If the STBD is actually hotter, then need to do some testing.

Check the heat exchanger (HE) tubes to see if they are clean.
If there clean then place a short piece of clear hose at the HE where the pump supplies water. Your looking to see if there are bubbles

Do agree those water pressure sensors are not reliable
 
Thanks Alec A, appreciate your reply. I do boat in salt water, but do a fresh water flush after every outing. I'll try to locate these Water Pressure sensors, believe you are talking about the back, top end where there are numerous other sensors and plugs? Am hoping maybe they are labeled, kind of like the pre and post O2 sensors and temperature sensor on the exhaust manifold? Might just swap it out to see. THX
Steve
 
The sensor is on the power steering cooler

Note: you mentioned 8.2 and 496. The 8.2 is a 502 and the 8.1 is a 496.
 
Excellent information shared on this thread. I'm the original owner and after a year two the water pressures on my 8.2 HOs began to differ by 4 to 18 lbs, RPM dependent. I don't know to this day if one engine water PSI is higher or lower than the other. I contacted Mercury Tech and she shared what the "normal" pressure ranges of which I fell within. She wrote not to worry that they are different as long as both engines were in the range shared. Further, I could replace or swap the sensors to see if the pressure readings moved with the sensor. I haven't done that due to the effort to reach them. My curiosity / concern has been satisfied for now.
 
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