Oil Pressure alarm in 2001 Z275ST with 6.2L

***300sflyer*** · 03-30-2011, 11:52 AM

Quote:

Originally Posted by csterner

Thanks for all the replies! I haven't been to the boat since last Sat. I am hoping to haul her home this weekend and then I can really take a look at the sensors and report back what I find. What test would you do on the sensors? Just a straight resistance check? Or watch for fluctuating voltage?

Simple... First check the outdrive fluid level. If it’s low, bring it up to full. Next, run the engine with your garden hose and the muffs. [no higher than about 1200 RPM and drive lowered down] If and when the alarm goes off, pull the sensor wire off each sensor one at a time till you find out which one is triggering the alarm.

For the drive oil, there are two connectors on the bottom of the bottle. Just pull one apart. The oil pressure sensor is located just above the oil filter on the port side of the block. The high temp sensor is located on the thermostat housing. Both have a simple push on connector.

csterner · 05-19-2013, 05:45 PM

Wow, it took me forever to find this old thread! Here is an update on this issue. Took the boat out yesterday and ran like a champ. When I came off of the throttle, my oil pressure would drop to zero on the gauge and the alarm would sound. I just replaced my oil sender unit a couple months ago. This is the first time the boat has been in the water since then. There were no knocking sounds and it was running fine. After a minute or so in the no wake zone, the pressure came back up. So then I started playing around with it to see. If I throttle down REALLY REALLY slow, the pressure would drop, but not all the way to zero. If I was at half throttle and came off throttle hard, it would drop but not to zero. Only when I was 3/4 to WOT and came off throttle, did it drop to zero. When it did drop to zero, I also tried putting it in neutral and revving it up. The pressure would go up as I revved up, but then drop right back to zero. Its like it just needs a full minute to relax and get back to pumping oil! I checked the oil sender to make sure the wire was seated on there correctly and it was. Oil levels are fine and oil was replaced when I put her up for the winter. I am really hoping it is not the oil pump....

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***Hudson River Steve*** · 05-20-2013, 02:55 PM

Hi Chris,
Not sure about your 6.2L but big blocks like my 7.4 MPI have a minimum spec of only 4 PSI of oil pressure at idle and a minimum of 30 PSI @ 2000 RPM. Have you tried putting a mechanical gauge on the engine to get a real reading? The sender/electrical gauge may not be accurately calibrated @ low pressures. If you truly had zero oil pressure the first thing you would hear are the lifters tapping and then the crank knocking.
Another thought - what type of oil are you running? If the viscosity is low, it may be heating and thinning out while you are at WOT...then takes a while to cool off and thicken up when in the 5 MPH wake zone. Since I am only a fair weather boater (above 50 degrees)...I only run straight 40 weight oil.
A third thought...is your oil level a little on the high side? If so, you may be getting some foaming of the oil while at WOT. It may take some time for the foaming to dissipate. I make sure to leave the oil level below the full mark. You could try sucking some out through the dip stick using an oil change pump and see if the process goes away. Just a thought.

csterner · 05-20-2013, 03:08 PM

Hey Steve! I use Mercruiser 20w-40 oil only. I haven't used a mechanical gauge to test. Unfortunately, I cannot recreate the issue on the trailer, so I can only test it while out on the water. I will see if a marina will rent that gauge or if I should just buy one.

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jsewall82 · 06-01-2013, 05:36 PM

I just brought my boat out for the first time this season. The alarm is going off. Had boat already serviced about a month ago and all fluids are good. Where are the sensors? So I can test which one is bad.

csterner · 06-01-2013, 07:07 PM

The oil pressure sensor is a bulb shaped sensor that screws into the side of the engine block. On mine, it is located on the port rear side of the engine just above the oil pan. It is a pain to get to. The temp sensors are located on your thermostat housing. I had 2 on mine. And the oil reserve sensor is located inside your outdrive fluid reservoir.

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***mikeyt*** · 06-01-2013, 07:43 PM

Quote:

Originally Posted by jsewall82

I just brought my boat out for the first time this season. The alarm is going off. Had boat already serviced about a month ago and all fluids are good. Where are the sensors? So I can test which one is bad.

You might want to double check the outdrive fluid level first though.