Hi guys, does anyone know what the correct type of tubing for a mechanical oil pressure gauge should be? Can I use rubber fuel line? What's the maximum length for the tubing? I think 5-6 feet would get the gauge where I want it.
Mechanical oil pressure
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It depends on the rating of the fuel hose. When I relocated my oil pressure senders/switches off the engine to a bulkhead I used hydraulic hose, 300 psi rated available at NAPA. Be sure to use a proper hose barb fitting in the block.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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hose length
Al: I'm wondering if hose length accounts for your grease gun hose working and mine not working. I'm guessing that for me the run from the block to the meter was about 3.5 feet. Kevinstone estimated he needs 5-6 feet.
Also, how hot do you run?Marty
1967 Tartan 27
Bowen Island, BC
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Originally posted by Kevinstone View PostHi guys, does anyone know what the correct type of tubing for a mechanical oil pressure gauge should be? Can I use rubber fuel line? What's the maximum length for the tubing? I think 5-6 feet would get the gauge where I want it.
5-6 feet should be no issue. I could see a really long line on a really cold day giving false low readings.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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I hooked up an oil pressure gauge on my old VW bus. I ran that plastic extension tubing from the engine (in the back) all the way to the dashboard. It was at least a 10 foot run. I bled the tubing and had oil all the way to the gauge. It was so accurate I would see the oil pressure drop as I shifted.
That was for a 67 bus a long time ago.
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heat and length
Trying to understand why other hoses have worked.
Found the hose that I initially used for the oil pressure gauge: 4 feet long, 300psi grease gun hose. There is no doubt it caused the gauge to receive misleading pressure. Running at temp for a couple hours on a hot day the reading fell steadily from 20 to 8. (Same gauge directly on the block worked perfectly, and when reinstalled with a copper tube works fine.)
I do believe that running at 180 with a long run caused the hose to get too soft to maintain the pressure the rest of the system has. perhaps others are running at a lower temp or have a shorter run? Or my hose was defective (unlikely)?
There is no flexible connection at either end.Marty
1967 Tartan 27
Bowen Island, BC
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Originally posted by Marty Levenson View PostTrying to understand why other hoses have worked.
Found the hose that I initially used for the oil pressure gauge: 4 feet long, 300psi grease gun hose. There is no doubt it caused the gauge to receive misleading pressure. Running at temp for a couple hours on a hot day the reading fell steadily from 20 to 8. (Same gauge directly on the block worked perfectly, and when reinstalled with a copper tube works fine.)
I do believe that running at 180 with a long run caused the hose to get too soft to maintain the pressure the rest of the system has. perhaps others are running at a lower temp or have a shorter run? Or my hose was defective (unlikely)?
There is no flexible connection at either end.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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Originally posted by Kevinstone View PostThanks for all the tips. I am leaning towards copper from engine with a short piece of fuel line at the gauge. Still
Need to see what I can find. Currently drifting around the keys, will check next time we land at a town. Is it necessary to bleed the tubing up to the gauge?
You need to find a good hardware store, hydraulic shop, or perhaps NAPA. Grease gun hoses work and our local hardware store makes up all kinds of high pressure hydraulic lines with various fittings. You need something that can deal with hot petroleum products at 100 PSI.
This is also likely why electrical oil pressure gauges are commonLast edited by joe_db; 01-22-2019, 03:43 PM.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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KS, An auto parts store should have a copper tube kit for exactly this purpose. I think I got one at an Advance Auto store. The copper should be more accurate and less prone to failure than plastic that typically comes with the gauge, although I have used both..when I was a kid and broke, it was a plastic tube thru the firewall to my gauge set on the '78 Civic. On my current project car, a '91 Civic, I 'upgraded' to copper when I installed an OP gauge.
And yes, you'll want to bleed it so you don't have air in the line, which could affect accuracy.-Shawn
"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
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Hmmmm..
Originally posted by joe_db View PostEven if the hose blows up like a balloon the pressure should be the same at the other end. This does not make a lot of sense
I'm curious because I can't see another explanation for my experience with the 4' hose, as stated in a previous post.
Question please: is anyone running at 180 with a longish non copper connection?Marty
1967 Tartan 27
Bowen Island, BC
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