Went for a run yesterday an noticed the port oil pressure gauge on bridge and lower helm was 80+psi. That is max pressure on the Teleflex gauge.
(Normally the port pressure is "higher" and comes down after engine warms up but not this time)
Put both engines to neutral and idle and pressure still maxed. Gave port engine some gas and the needle wanted to go beyond 80psi.
I figured this was bad oil sending unit.
We decide to shutdown and check oil, and wiring etc. Everything at sending unit looked good. Oil was clean etc.
After drifting for about 30 minutes started up and headed back to dock. Shortly after starting and running up to speed the port oil needle slowly, very slowly, began to drop. Then out of no where the tach bounced to zero and back (engine remained at full power), then the entire port gauge cluster went dead. No temp, oil, volts or tach. This only happened on the port side and the engine did not miss a beat. Then a couple seconds later everything came back and the oil pressure was the same as the starboard side. All other port gauges were same as starboard.

I have to study the wiring diagram for the engine and take into consideration the lower helm. Somewhere the wiring plug from the engine must be split and run to each helm. The plug on the bridge looked clean and the plug on the engine looked clean. I will have to check the lower helm plug next. Going by the engine wiring diagram I think all the signals wires are independent so a bad engine oil sending unit should not affect all instruments. I could be wrong, the diagram is poor.

Seems like there are 2 problems? 1 wiring and another bad oil sending unit.
Anyone else have any ideas?

-Karl

I have not gotten that far on my boat project yet. But the tractors that I have restored, when you lose a cluster of instruments, I always check the ground first. 85-90% of the time the ground is the problem. If you don't have a good ground nothing will work.

Just my two cents.

Good Luck, Michael

While WD40 ain't a lubricant, it sure it a moisture displacer. This may be one good use for it. I think the OP's oil pressure flakiness is probably a loose or corroded wire. But just for kicks, have someone jiggle the wire at the sender while someone else eyes the gauges at cabin and bridge helms. Then try the same at each connection point along the wire including any multi-wire connector. And because the tach is unstable, the thought of a ground wire fault is something to check the same way.

Hope you'll tell the group what you discover.

Two causes most likely:

1. Moisture on wiring terminals (mine get flaky all the time...tachs mostly.)
2. Moisture an crude on terminnals on bridge terminal block.

I finally had to replace both my org. tachs on the FB. Both got wierd all the time. I replaced with some NOS I had and they are fine again.


Volt meters are know to fail with age and moisture I have replaced several over the past 8 years.

Oil pressure guages can do the same thing if moisture gets inside the case.

Complete shut down of one side is most likely poor ground or hot connection on terminal block on bridge.

dave

With only 0.9 to 1.02 volts (preferred range) you MUST have excellent connections.

Jeff

Agreed. For a complete panel to have a problem it must be a bad ground.

I found a #16 wire connecting all the grounds on the Fly Bridge console, worked OK until I had everything on then things started acting funny, bad readings, lights dimmed, replaced with a larger wire and all is well. Found that While trying to install a sterio and couldn't get the ground to make the sterio work right, when I grounded it to the aluminum frame it worked great. Jack.

Hope you didn't use the frame as a permanent ground....

Someone correct me if I'm wrong....nothing should be grounded to the frame! All grounds go to grounding block which goes to engine ground...correct???? Grounding to the frame causes corrosion

Ok let me try and dispel a myth regarding 12 volt negative grounding on our boats.

Here is a simple test....

1. Take a test light or voltmeter and touch it to the positive post of one of your batteries and the negative to a stringer..

MAGIC.. you will read the voltage from the battery.

2. Trace the main ground wire from the battery(s) and you will find it terminates with a bolt on a brace on the bulkhead which is welded to the stringer thus to the frame!

3. Continuity check from Alternator to hull yes... it will have continuity!

The difference is no DC voltage is allowed to flow directly to the hull if you have a galvanic isolator properly installedon your AC green ground. The AC current flows through your neutral and not the ground. Now if you were to jump from the black postive to the ground it would show voltage sine you provided the route for it to flow through.
NEVER DISCONNECT THE GREEN GROUND WIRE FROM YOUR SHORE POWER. Very dangerous!

So where is the confusion? electronics etc should route to your ground bar on you electrical pannel..why you ask.. it is suppose to be a clean connection to ground. (Brass bar etc.) Corrosion on the DC negative grounds or positive increases resistance thus load..heat.. and can even cause a fire. (toaster syndrome)

Now with our aluminum boats.. we need to maintain isolation from dissimular metals.

Two disimular metals in a medium (salt water is the best or contaminated fresh) creates a battery. One becomes a cathode the other the anode. In the case of our boats the alluminum becomes the anode and sacrifices to save the bronze, steel etc.

This isolation interrupts the continuity from the hull, engine etc. thus there is should be no bonding on our shafts and any dissimular metals on our boats. Thru hulls, props shafts etc.

We add anodes to compensate for any continuity between metals. Even if you had a bonded shaft you could add enough andoes to protect it but it is difficult so isolation is much simpler and cheaper.

DC leakage is a major contributor to galvanic corrosion. (or electrolysis) One culprit is often bilge pump splices that are in bilge water and not water tight. small currents can flow through the water between the splices and corrosion can begin.

DC leakage is what we wish to avoid.

Confusing I know but check your boat out and it will be wired pretty much as described.

Have a great fall and winter,
dave

Dave - Am I wrong in remembering that cathodes give off electrons and anodes collect/accept electrons(back to tube theory)[remember tubes?].