What kind of motor oil do you use?

[hanleyclifford]

We have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.

[hanleyclifford]

What's with all the dotted lines in the posts lately?

[JOHN COOKSON]

so are you guys seeing higher pressure at start up and then a decrease after the engine warms up?

Another yes.
This is why it is recommended that oil pressure be adjusted when the engine is fully warmed up at cruise RPM.

TRUE GRIT

[jbsoukup]

I could have sworn I saw higher pressure with lower viscosity oil and it seemed counterintuitive to me also.
I assumed lower viscosity = lower pressure = higher flow rate but my observation (as I remember it) was opposite, pressure wise.
I don't really worry about it as I never see pressure drop below 20 or so at any time.
not sure how we could measure flow rate anyway

[jbsoukup]

Mo, same with me. I try to be in around April 15, and water temps are high 30s to low 40s. Got a big fur hat and an Irish wool sweater for those days.

[JOHN COOKSON]

I Assume You Have An Electric Gauge?

I could have sworn I saw higher pressure with lower viscosity oil and it seemed counterintuitive to me also.
I assumed lower viscosity = lower pressure = higher flow rate but my observation (as I remember it) was opposite, pressure wise.

Try a new sending unit. Or something. With this weird stuff going on how can you be sure what your OP really is?

TRUE GRIT

[joe_db]

I see them in IE but not in Firefox.

What's with all the dotted lines in the posts lately?

[joe_db]

My current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.

My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.

We have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.

[hanleyclifford]

My current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.

My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.

Next time you have your oil pan down have a look and a measure of that fitting. On my engine the ID of the ell was significantly smaller than the oil pump discharge channel. I posted the figures here a while back. I'll look for the post.

[hanleyclifford]

This thread has some useful info: http://www.moyermarine.com/forums/sh...=9581#post9581

[edwardc]

What's with all the dotted lines in the posts lately?

They're ToolTips, another great feature our Admin has set up. Commonly used, but sometimes obscure, acronyms get underlined. Hover over them with the mouse pointer to see the the full text for things like UHS, IMHO, and IIRC.

I see them in IE but not in Firefox.

Interesting. I see them fine in Firefox (on a Mac).

[hanleyclifford]

My current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.

My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.

Here are the measurements I made at the time I switched to 1/4" NPT ell for the oil pickup. The oil channel thru the bearing cap measures .285". The hole thru the strainer frame measures .266". But the 1/8" NPT street ell connecting the pump to the frame only has .187" ID! That was enough to sell me on making the change.

[BadaBing]

After my partial rebuild early spring 2015 & having done at least 6 serious lil system flushes, I adjusted the oil pressure bypass in because i was seeinf pressure holding at about 25 - 30 lbs. After the adjustment I saw 35-40 lbs. Then I drained my last clean oil , something cheap and common, 10-30 and filled her up with 15-40 Rotella. Did a few more odds and ends which allowed the engine to cool down and give her a start.
The start up pressure shocked me at 70lbs right off the bat. Then quickly drolped to 60. I thought I waz going tl need to adjust the.pressure down. However, after warming up the pressure dropped back to hold.between 30-40 under normal opperation .
Obviously 60-70 is way too much but Im now wondering if opperation 30 & 40 is ok.

[JOHN COOKSON]

Mr. Bing
Here is what Don M. recommends on page 5-4 & 5-5 of the Moyer Manuel.
Dress up the seat of the regulating valve every 5 years or more often if necessary. Did you dress the seat as part of the rebuild?
Then readjust the OP to ~ 50 PSI cold idle then (more importantly) 40 PSI with the engine warmed up at your cursing RPM.
And on page 5-4: "As long as the OP at idle is ~ 1/2 the OP at normal cruise all bearings as well as the oil pump are in reasonably good condition."
Hope this helps.

TRUE GRIT

[jbsoukup]

I replaced all the engine wiring for the 2014 season so I know that is good.
I'm thinking the only way to be sure of correct oil pressure is to install a new gauge and matching sender.
Catalina Direct has a nice oil pressure gauge which matches the fuel gauge I installed last season, but the sender is metric thread.
Will any sender work?