Who makes the most accurate and reliable mechanical oil pressure gauge ?

[Milacron]

By mechanical I mean, reading is taken directly from oil flow to the gauge. What I have in the engine room is Murphy 20P-150. One of them has failed. Tried cleaning it internally with carb cleaner...helped for awhile but now back to reading 5 lbs (when pressure really is 35+ lbs)

When I did a gauge swap between engines I noticed the working one was obviously newer, so this isn't the first Murphy failure in the boat's history.

Therefore wondering if I should order another Murphy or some other make. (for 2" nominal opening)

 

[dsharp]

We used Stewart-Warner marine series

 

[Avenger]

I would avoid Stewart-Warner. Mine have been a big disappointment.

 

[GJH]

I would avoid Stewart-Warner. Mine have been a big disappointment.

A) How so?

B)Mechanical or electrical?

 

[captddis]

I agree. The last few SW mechanical gauges were not accurate and had to return one right out of the box.

 

[34Hatt]

I agree. The last few SW mechanical gauges were not accurate and had to return one right out of the box.

Another company that went down hill they use to be one of the best many moons ago though.
Most likely went the China route

 

[Avenger]

Mexico.

Electrical gauges, two had defects right out of the box, and the bezels on the "Marine Deluxe" tachometers developed bad rust after about a year.

 

[GJH]

So what's that leave, Murphy, Isspro and VDO? Have had good luck with the last two, no direct experience with Murphy though they have a good rep.

 

[MikeP]

The difficulty in such a discussion re "accurate" gauges is the fact that most commonly available/purchased gauges are not calibrated and most people don't have any way to calibrate a gauge.

IOW, if your new gauge shows X pressure at Y RPM, how do you know that that is really the correct pressure. The answer is, you don't. Test gauges that are calibrated that can be used to provide really accurate readings cost around 1000 bucks. Fluke, as well as other manufacturers, make such gauges.

We normally assume that mechanical gauges are more "accurate." But, in reality, although they are not subject to variations in voltage/wiring/connection issues that can effect electrical gauges, the specific reading can still be substantially in error. OTOH, the RELATIVE readings of the mechanical gauge are likely to be consistent.

 

[GJH]

The difficulty in such a discussion re "accurate" gauges is the fact that most commonly available/purchased gauges are not calibrated and most people don't have any way to calibrate a gauge.

IOW, if your new gauge shows X pressure at Y RPM, how do you know that that is really the correct pressure. The answer is, you don't. Test gauges that are calibrated that can be used to provide really accurate readings cost around 1000 bucks. Fluke, as well as other manufacturers, make such gauges.

We normally assume that mechanical gauges are more "accurate." But, in reality, although they are not subject to variations in voltage/wiring/connection issues that can effect electrical gauges, the specific reading can still be substantially in error. OTOH, the RELATIVE readings of the mechanical gauge are likely to be consistent.

A good mechanic/surveyor will do it as they don't trust any gauges on board.

 

[Milacron]

A good mechanic/surveyor will do it as they don't trust any gauges on board.

True but how do we know their gauges are right either ?? In fact I had this done on the port engine a day after the survey. Mechanic connected perhaps 3 foot line with mechanical gauge at the appropriate block outlet (probably where the Murphy gauge line was connected) and his gauge read nearly 40 psi at idle speed ! Now that I know more, it seems unlikely it was really that high at idle... 32 maybe...but 40 ?

 

[Milacron]

Mexico.

I think the Murphy's are now made in Mexico as well. Today I ordered a new old stock one off eBay...hopefully it is old enough to be USA made. The seller has 9 more of them, so if the one I get seems accurate I'll order two more....one extra so both engines will show the same range and a third one for spare.