Oil Pressure Gauge

[jayski81]

The oil pressure guage on my 1977 vintage Atomic IV flips to maximum immediately upon engine start-up. The boat is new to me and the mechanic gave the engine a clean bill of health in the pre-sale inspection. I'm guessing that the pressure is fine but the sensor is faulty. Any suggestions on how to proceed? We are out of the water for the season and I do not want to go into next season without addressing this issue.

[Don Moyer]

Each manufacturer of gauges tends to match their gauges to their own sending units. Therefore there are variations between manufacturers in terms of what happens to make a gauge flick to either a full right or a full left indication, but in general, a full movement one way or the other would indicate that the wire from the sending unit is either shorted to ground, or open.

In either case, the first thing I would do would be to check the sending circuit very carefully. If the wire disappears into a wiring harness, or is otherwise not visible much of the way to the cockpit, you might run a temporary wire between the sender and the gauge. If the gauge then operates normally, you will know that you'll have to troubleshoot the original wire further, or replace it permanently.

[Fred]

Don, is there another way to check oil pressure in the event of a faulty gauge?

Is there somewhere on th engine to attach a temporary oil pressue gauge?

thanks

[randall]

There is a slotted plug directly behind the carb (late model) on mine. I busted the threads on the regular spot where the pressure sender goes... Don told me this spot was just as good.

I used a 6" high pressure rubber line, and put my sender on that.

It took an impact driver to get the plug out, and THAT was kinda' scary to be banging on the side of the block.

My oil pressure gauge is nice and steady.

So take the carb off, and you'll see the location you're looking for.

[Fred]

Thanks, we'll take a look at it.

Fred

[lewis1719]

Is it opossible toremove the sending unit an connect a gage there to double check oil pressure. I have asimilar issue. My gage runs at around 70 to 80 psi.

[tenders]

Sure you can do that. You're essentially replacing the sending unit/gauge combo with another one which might be just mechanical, right?

[Sony2000]

My guage reads 80 as well, but my mechanical guage, from Lowes type store, plumping department, water pressure gauge, $8, is reliable for now. Maybe a wholesaler has a water temperature guage!

[lewis1719]

Yes, I have a water pressure gage I could put in just to confirm the reading on the cockpit gage. If it is still reading high then I will adjust it down to around 50.

[hanleyclifford]

I keep 3 or 4 direct read OP gauges on board with two always installed at different points in the system. By moving them around once in a while I can learn who is telling the truth; liars get replaced for about $10 each.

[Whippet]

OP gauge in cockpit consistently read 20 psi -- and didnt move much w RPMs. i assumed faulty sending unit, so installed the Moyer guage the goes right into block. darn, same consistent 20 reading.

so i figured time to take on the adjustment mechanism. The lock nut was frozen to adjusting bolt - but wasnt frozen at the block -- so i pulled whole mechanism. Geez, spring protruded from resulting hole. Was hoping that ball at other end wouldn't run off into block somewhere.

Plopped the threads in a cap-full of PB blaster and lock nut came free. Gave adjusting screw 3-4 twists clockwise and re-installed. Fired up - and OP was about 20 at fast idle, 30 at "low-medium" RPM, and 40 at "higher medium" RPM. (sorry, no tach).

All sound about right? what is experience with how many turns of adjusting screw is right number?

I was nervous as a cat at point whole mechanism was out and spring exposed -- but i had comfort that if i got into a bind you guys would help

Thanks

[JOHN COOKSON]

Sounds good.
If you have the Moyer manual see page 5-5."OP should be ~40 PSI at cruise power setting with the engine fully warmed up. Idle PSI should be ~1/2 that."

TRUE GRIT