low oil pressure/overheat

G

greenstreak

New Member
Nov 1, 2008
86
I have a 2000 mercruiser 7.4 mpi. I have had a diagnostics check twice on my engine. The first time was when buying boat. The low oil pressure and overheat code was thrown. the mechanic reset them and told me he could find nothing wrong. My oil pressure always shows over 40 psi when cruising and 20 psi when idling. My overheat alarm has never gone off. I just had the mechanic to check again this week and the codes are thrown again. Still I have had no alarms going off. I have had no signs of any overheating. the engines runs good. Any ideals what is causing this. the mechanic said it could just be any little thing causing the codes to throw.

Thanks
art
 
They only way to tell when these codes are thrown is to connect the diagnostic box to the MEFI 3 processor and monitor it. MEFI 3's diagnostics are rather simplistic.

Best regards,
Frank
 
The first thing i would do is diligently ck. clean and tighten all ground circuits, i.e. batteries, eng. and all buss bars as the integrity of these are imperative to the proper operation of any electronic engine control system.
 
If you are worried, do you have a digital or electronic dash. I would consider using if even for temporary installing a manual "stand alone" water temp and oil pressure guage. even if you place them in the engine room you can have sombody check em out if you don't trust the electronic ones.

She may be "flashing" a high temp and low oil. Either that or she's running border line as she warms up. Example My CAT in my Peterbilt will show a code for high water temp but will not set off SHUTDOWN alarm until "Very high water temp". However the high temp will set as a trouble code.
 
MEFI 3 is an analog electric gauge panel. No SmartCrap. Sea Ray also does not wire in the "Check Engine" signal lights. So when MEFI 3 senses a problem, it records the flag, but you don't know it until someone plugs in a scan tool. Unfortunately, my Mercruiser manuals are on the boat and I forget how to add the signal lights.

Best regards,
Frank
 
Last edited:
fc3 said:
MEFI 3 is an analog electric gauge panel. No SmartCrap. Sea Ray also does not wire in the "Check Engine" signal lights. So when MEFI 3 senses a problem, it records the flag, but you don't know it until someone plugs in a scan tool.
Click to expand...

Or until it "sounds expensive" or a connecting rod is sitting in the bilge. My not be the best design.
 
Well you still have the analog gauges on the helm and if the boat has the optional systems monitor panel, that'll signal when an overheat or low oil pressure fault is detected. Those faults are triggered by switch closure senders mounted on the engine. Thus engines equipped with the monitor have an analog sender for temp and oil pressure and a binary switch closure sender for temp and oil pressure. If he's not getting a warning on either system, then it's an electronic fault. Probably noise on the electrical system.

Does the boat have anything unusual on the DC system? Especially stuff not installed by Sea Ray.

Best regards,
Frank
 
Has he concluded that he does not actually have both conditions. IE angine getting warm and thinning out the oil. Not to a danger but enough to throw a code. Some folks really don't wanch the guages. How hot does the ECM consider too high? And same with low oil. How low is too low?
 
Don't know. My manuals are on the boat with the scan tool.
 
hey guys--I have finally found out that my engine was running hot. the alarm that has gone off I thought was low outdrive, but it was my overheat alarm. I thought my dash gauge was bad but it is correct. Now I am trying to figure out why it is overheating.

Thanks

art
 
My system monitor had an issue where it would sound the low oil pressure alert, but my gauge was fine.

This was checked over and over again until I finally found the separate switch used just for the the monitor, different than that for the gauge.

The factory wired to that oil switch threaded electrical connection stud w/ a push-on connector that stopped maintaining spring pressure on the threaded stud.

That defective push-on connector was snipped off and I crimped on a ring tongue connector and retained that w/ a nut.

No issues since.

Are your issues on the system monitor or the gauges or both?

There are different sensors / switches / wiring for each indicator.
 
This is an off the wall question but being that I/O and inboard boat engines are similar to automotive applications, what sort of scan tool is used? Do boats use the same OBD1 and OBD2 plugs/diagnostic systems as the automotive apps? Or is there a special scan tool you have to buy from the manufacture?


Be easy, I'm an automotive guy who boats as a hobby. :lol:
 
Bad Impeller/Seawater Pump? Clogged Seawater intake? Have your checked your Seawater PSI?
 
Beer Thirty said:
This is an off the wall question but being that I/O and inboard boat engines are similar to automotive applications, what sort of scan tool is used? Do boats use the same OBD1 and OBD2 plugs/diagnostic systems as the automotive apps? Or is there a special scan tool you have to buy from the manufacture?


Be easy, I'm an automotive guy who boats as a hobby. :lol:
Click to expand...

Different. The GM MEFI systems require a specific scan tool. Mercruiser's SmartCraft systems probably require a special tool. I have not tried to diagnose a Smart Craft system but since Merc likes proprietary solutions, my guess is that you need a proprietary tester.

Rinda makes some good ones. The Rinda tester that I have for the MEFI-3 ecu on my 7.4 MPIs can be upgraded for Smart Craft, which I've not done.

Best regards,
Frank
 
The Mercruiser scan tool also requires an engine-specific module. It is very handy for checking and working on the engine.

The Mercruiser fuel pressure tool is also handy.

A side benefit is these are used when I commission in the spring to purge air from the fuel lines, as I run dry in the fall. The old way was to crank and crank 'till it started.
 
The Mercruiser tool was also used when I cleaned my injectors.

It has a cable that drives the injector directly. I removed the injector, shot it w/ spray start, then compressed air, while the tool sent it a series of pulses.

Then I repeated w/ WD-40 and air.

This went back and forth several times and I saved myself ~$100 x 16 and restored proper performance.

I needed to replace several o-rings that couldn't be reused when replacing the injectors into the block.

This process worked great! I could see them change from okay to just fine. This service has held up well over the years too.
 
I have a Rinda Scan Tool and with the adapter it will work on the PCM555 and ECM555 computers (SmartCraft).
For Info go Here http://www.rinda.com/marine/mtspec.htm

The Rinda is the one recommended in the Mercruiser Service Manuals.

To work on the PCM555 or ECM555 download Service Manuals #33 or #36 one is for BBC and the other for SBC.
 
You must log in or register to reply here.

Forum statistics

Threads
113,163
Messages
1,427,598
Members
61,072
Latest member
BoatUtah12
Back
Top