Oil pressure gauge repair?

[jfhallst]

I have an '88 Osprey 170.  Up 'til this spring oil pressure gauge was working fine.  Suddenly stopped registering.  No movement at all.   Took off panel and discovered that sensor appears to have been replaced (new wire run to engine ('95 75hp Mariner) outside original harness.  Oil pressure "tweet" happens when key is turned on.  Don't ever get a low pressure warning.  I'm assuming sensor at gauge is bad?  Haven't been able to find out where to get a replacement.  Can anyone help (including telling me if the problem is likely to be at the engine end rather than at gauge?)

[fitz73222]

I have an '88 Osprey 170.  Up 'til this spring oil pressure gauge was working fine.  Suddenly stopped registering.  No movement at all.   Took off panel and discovered that sensor appears to have been replaced (new wire run to engine ('95 75hp Mariner) outside original harness.  Oil pressure "tweet" happens when key is turned on.  Don't ever get a low pressure warning.  I'm assuming sensor at gauge is bad?  Haven't been able to find out where to get a replacement.  Can anyone help (including telling me if the problem is likely to be at the engine end rather than at gauge?)

There is no oil pressure gage on a 1995 75hp Mariner. Its a 2 cycle oil injected engine.  do you mean the low oil warning horn?

[jfhallst]

I'm talking about the cockpit end.  One of the gauges in the gauge set above the steering wheel says "oil pressure" and it's always registered a pressure when the engine is running.  Now it does nothing.  Just trying to figure out whether my problem's at the gauge end or the engine end (there must be something on the engine end that's sending oil pressure info to the gauge)

When I turn on the key, there's always a short "tweet" sound, which I assume is a test signal from the low oil warning horn. (My engine has the oil tank right on it, there is no remote tank.)

[fitz73222]

Are you sure you don't mean "water pressure" gage?

[Capt. Bob]

I'm thinking Fritz is correct on the water pressure gauge.

Can you see the back of the gauge? Does it have a black tube attached?

Water pressure makes the most sense since it quit outright. There may be a blockage in the tube or at the gauge itself. The tube may have popped off at either the motor or gauge (you may see water collecting under the cowling or at the helm). If the water pump is in need of service, you may see a "0" reading when on the flushing muffs. You should see a little while underway from the pressure being forced through the engine. That is unless one of the situations listed above is present.

I'm not one of our resident piston heads but I can't recall seeing a two stroke engine having an oil pressure gauge because of the nature of its design.

Good luck.

[wingtime]

I'm going to go out on a limb here and say that a previous owner installed a automotive oil pressure gauge and sender for a water pressure gauge.  As already mentioned a true water pressure gauge for that era is a mechanical gauge that has a small water tube running to it from the engine.  The beeps you are hearing are part of the warning system and come from a dedicated horn that is connected to the alarm module on the motor.  Besides the start up test beep a continuous BEEEEEEEEEP means overheat and a beep beep beep beep ususlly means oil injection issue.  There is a chart that explains the different warning horn beep code.

[GoneFission]

That would be interesting!  Put an oil pressure sender on the water jacket port, run a wire up to the gauge and use an electrical oil pressure gauge instead of a mechanical water pressure gauge?  That could work!  Water pressure at idle is usually around 5 PSI, but it would read on a 40 PSI oil pressure gauge.  As noted above, there is no oil pressure on a 2 stroke engine, but someone could have done what is described above. 

Here is the list of warning beep codes for mid-90s motors: 

LOW OIL LEVEL: The low oil level warning is activate when the remaining oil in the mounted oil reservoir tank drops below the float switch.... WARNING HORN EMITS A SERIES OF FOUR BEEPS for EFI, BEEPING UNTIL YOU DO SOMETHING for carb motors.

ENGINE OVERHEAT: HORN SOUNDS CONTINUOUSLY

ENGINE OVERSPEED: INTERMITTENT BEEP until engine speed drops below MAXIMUM RPM.

ELECTRICAL SENSOR NOT FUNCTIONING: If the TPS, MAP, or CTS is not functioning, or is out of it's "pre-programmed diagnostic range", the warning horn will sound INTERMITTENTLY.

WATER IN FUEL WARNING: SERIES OF FOUR BEEPS (again for EFI motors)