Another Oil Pressure Question

[sybaris2]

I have a 2005 Mercruiser 260hp 5.0L MPI with a little over 200 hours. I replaced my oil sender yesterday so now that gauge is working but it's revealed that even just idling around the lake at 700RPM my pressure is about 75psi. After I replaced the sender I changed the oil with the usual 25/40 and required filter. Is there anything easy to check before I have to haul her out to the shop?

thanks

 

[Bt Doctur]

bad sender maybe

 

[alldodge]

Your saying prior to replacing the sender the gauge was not working at all?
What part number was the sender?
Is there full battery voltage on the gauge at the purple wire?

 

[sybaris2]

Your saying prior to replacing the sender the gauge was not working at all?
What part number was the sender?
Is there full battery voltage on the gauge at the purple wire?

Gauge was not working. It quit last year.
Sender P/N: 8M0068784
Haven't checked the purple wire

thanks

 

[tank1949]

I have a 2005 Mercruiser 260hp 5.0L MPI with a little over 200 hours. I replaced my oil sender yesterday so now that gauge is working but it's revealed that even just idling around the lake at 700RPM my pressure is about 75psi. After I replaced the sender I changed the oil with the usual 25/40 and required filter. Is there anything easy to check before I have to haul her out to the shop?

thanks

Perhaps sender incompatibility with gauge or indeed inaccurate? Incorrect ohms? You can purchase a manual sender with flexible tubes and pipe fittings and compare at motor. They are simple to install.

 

[alldodge]

The sender is for gauges from 0-80 psi
Could place a mechanical gauge to verify pressure. Many auto parts stores have a loaner program

Being a 2005 would the boat happen to have smartcraft?

 

[sybaris2]

The sender is for gauges from 0-80 psi
Could place a mechanical gauge to verify pressure. Many auto parts stores have a loaner program

Being a 2005 would the boat happen to have smartcraft?

Correct. It is the manufacturers recommended sender for that engine and matches the gauge.

Not familiar with SmartCraft so I looked it up. All my gauges are analog so no, don't have it.

 

[alldodge]

Remove the sender wire and turn ignition ON, gauge should read zero, then ground the sender lead and it should peg meter high

 

[sybaris2]

Remove the sender wire and turn ignition ON, gauge should read zero, then ground the sender lead and it should peg meter high

This is the exact gauge in my boat.
Just to be sure.... the left post is the Sender, the center is G, the right post is ignition and the spade on top is for the light, correct?

 

[alldodge]

That is how I also would read it

 

[Scott Danforth]

factory gauges are merely a suggestion on probable oil pressure. always compare to a mechanical gauge.

 

[sybaris2]

factory gauges are merely a suggestion on probable oil pressure. always compare to a mechanical gauge.

Could I hook up one of those on my line going to my oil filter? The reason I ask is that the sender location is reachable only by small children. When I replaced the sender yesterday I did it blind.

 

[sybaris2]

Remove the sender wire and turn ignition ON, gauge should read zero, then ground the sender lead and it should peg meter high

Those are the readings I got.

So after doing some poking around I have read that high psi at low rpms can be one of several things...

1. Stuck oil pressure relief valve
2. Spun cam bearing
3. Faulty wiring from gauge to sender
4. Gauge inaccurate

Anything else?

1 and 2 would require pulling the engine and be costly. Are there reputable 3rd party insurance company's that cover such mechanical issues?

thanks

 

[sybaris2]

Those are the readings I got.

I did notice something different.
Before I started testing everything I turned the ignition on and the needle rose to about 10psi. Also when
I tested with the sender disconnected from the gauge the needle rose to about 10psi as well.
After I did the ground test and put everything back together I turned the ignition on and the needle didn't budge. So I started her up and just idled. The needle rose to 40 then to 65 and sat there. I reversed out of my dock and the needle went to 75. After I got away from the dock and gave a her a little juice to about 2000rpm the needle went to 80.
So maybe with the messing around I got the gauge to read a little more normal?? Still feel better doing a mechanical gauge pressure test though.

 

[tank1949]

Could I hook up one of those on my line going to my oil filter? The reason I ask is that the sender location is reachable only by small children. When I replaced the sender yesterday I did it blind.

What does pressure drop to after running for an hour? I'd expect 1/2 drop would be normal, like 30-40 at idle after motor is hot.

 

[alldodge]

Could I hook up one of those on my line going to my oil filter?

Yes

Before I started testing everything I turned the ignition on and the needle rose to about 10psi.

Sounds like a gauge issue or something is wrong with the power/grounding. Most likely its the gauge

 

[sybaris2]

What does pressure drop to after running for an hour? I'd expect 1/2 drop would be normal, like 30-40 at idle after motor is hot.

Haven't had her out for that long this year. I'll try it.

 

[sybaris2]

Changed the oil gauge. That was it. What a relief.
I had visions of thousands of dollars flying out of my billfold.
Thanks for everyone's suggestions.

 

[alldodge]

Changed the oil gauge. That was it.

Your first post said you just changed the oil (25/40), and just changing it again fixed it. OK

 

[sybaris2]

Your first post said you just changed the oil (25/40), and just changing it again fixed it. OK

No. After I replaced the sender the oil gauge started registering the pressure albeit incorrectly. Before it just sat on 0. So I had a bad sender. Yesterday I replaced the oil gauge and now the pressure is reading correctly. So I had a bad sender AND oil gauge.