Is oil pressure a good indicator of protection?

[USA_boater]

If the oil pressure is good (gold standard is 10psi for every 1000 RPMs), then is that a good indicator that the oil you are using is providing sufficient protection? So for example, in another thread, a guy said that running 20w50 in a 4.3 Chevy motor caused some kind of issue (overheating I think). I want to know if the oil pressure can tell you if the viscosity of oil you are using in your inboard motor is working for the given conditions? To take it further with the 20w50 example, can the gauge clue you in if the oil is too thick (or thin)?

It makes sense to me that if the oil pressure is not too high or low, that the oil is doing a good job lubricating the bearings but I wanted to ask those of you who know more than me. I'm not planning to run gear oil in my crank case, I just want to run a FULL synthetic oil and want to be sure the one I have won't be too thick. Thanks guys.

 

[tpenfield]

To some extent,, but engine wear also plays a part. I also think there is a relief valve that has a regulating effect.

 

[Lou C]

What I have used as an indication is how much your oil pressure drops from cold slow idle, to hot slow idle like after coming off plane. So if you're at about 40-45 at cold slow idle, then I'd like to see the hot slow idle, be in the range of at least 15-20 psi. If lower than that I might get concerned, even though 10 psi is enough for a Chevrolet small block at idle speed.....

 

[GA_Boater]

If the oil used is the oil meeting V-P's specs and the oil pressure is within the range V-P says it should be - What's the issue?

You have an oil fetish.This isn't an oil pressure thread. It's another oil thread - Again!

 

[Scott Danforth]

the minimum standard prior to requiring a motor to be dug into is 10psi per 1000 RPM. I have never had a healthy motor with less than 40 psi at idle. most every motor I build has over 60 psi at idle.

most oil pumps have a 50-70 psi relief pressure (most in the 60-70 psi range)

if 20W50 causes over-heat, then there is something else wrong with the motor.

if you want to run full synthetic then do so. boats are not cars. you could run straight 50 weight without batting an eye as oil temp goes up with load. boat motors are always loaded, and anything over 300hp needs an oil cooler.

oil pressure is related to bearing clearances, pump volume and oil viscosity in addition to shear modifiers and other additives as well as any contamination from the engine/combustion process/fuel/etc.

oil viscosity is tied to oil temp and oil base.

only an oil analysis will tell you if the oil you are using is offering good protection.

 

[Walt T]

You can buy oil analysis kits at most auto parts stores, The Napa I buy at has them. Or look online. I highly recommend these.

 

[Maclin]

Is your oil gauge mechanical or electric. A mechanically actuated gauge is needed to produce most reliable, accurate and prompt readings for giving you warm fuzzy feelings, or the other kind.

 

[USA_boater]

To answer Maclin's question, I'm not sure...I am thinking electrical though; I guess there would be a vaccum line or something on the back of the gauge if it were mechanical? The boat is a 2004 made in 2003 if that helps any?

Also, I've heard organic, extra virgin coconut oil was a good alternative for marine use...(just kidding).

Thanks for the replies fellas.

 

[Scott Danforth]

a mechanical gauge would be bolted to the engine.

a capillary tube would not be wise to run 20' away to the dash.

all factory OP gauges on the dash are electric

 

[jimmbo]

An oil pressure gauge only reads pressure up to where the gauge is located. While it can reveal a weak pump or high flow from high leakage(internal). It will give a false high reading if the oil passages downstream are plugged. I have seen engines showing plenty of pressure, but the valve train starved of oil.
I know a lot of builders would build their ‘race’ engines with greater bearing clearances that stock(better cooling was the reason/excuse), then to increase flow to cover the leakage, a high volume oil pump was added. If pressure was still low thicker oil was used. Well, the high volume pump and thicker oil both use more HP to turn. The greater clearances throw more oil onto the cylinder walls, oil consumption rises, carbon build up increases, the thicker oil flows slower potentially starving the bearings. Most marine engines these days are based on the Chevy SB and BB Chevrolet engineers did an excellent job in regards to the Oil System when they designed those engines. It is almost bulletproof, until someone ‘improves’ it.

 

[harringtondav]

Chevrolet engineers did an excellent job in regards to the Oil System when they designed those engines.

Hear-hear! I was talking myself into a 2footitus new boat. Until I learned Merc abandoned GM in my power range. By the time their new engines prove themselves, or bomb, I'll probably be driving an O/B pontoon.

 

[Lou C]

I don't know what Merc did with the new engines but that 4.5 liter V6 looks an awful lot like a GM 4.3 when you take all the peripherals off of it...

http://www.crowleymarine.com/mercury...s/16591_40.cfm <-----new Mercruiser block
http://www.crowleymarine.com/mercury-outboard/parts/7801_110.cfm <----when it was still GM


http://www.crowleymarine.com/mercury...s/16591_50.cfm <----new Mercruiser cyl head
http://www.crowleymarine.com/mercury-outboard/parts/7801_90.cfm <---GM cyl head

 

[aimlow]

Too much oil pressure can wear the distributor drive gear from too much force on the gear drivingthe oil pump. Besides, it's not pressure but flow. Too much pressure is unnecessary and undesirable. The oil temperature should also be over 200 degrees.

My standard response..when was the last time you saw an engine damaged from using the wrong oil?