70+ psi Oil Pressure? Is that a problem

[RidgeRunner]

Short version- Only after an oil change did I see a rise in Oil Pressure.
70 psi verified via analog gage at cruise speed. 45-50 at idle, depending on temp.:huh:


Another oil and filter change, same results. PCV replaced as well.
Standard M/C Oil (25-40w) w/ large capacity M/C filter.
Correct oil level.

QUESTION FOR THE MASSES-
IS THIS A CONCERN OR NOT ?

 

[Steve195]

I had a similar issue late last year when I suddenly noticed the gauge going to 75 at cruising speed, and pegged at WOT. Motor is 2008 Merc V8 5.0. I bought it early last season and it had a "certified used boat" warranty. I took it to my dealer, and they initially thought it would be the gauge or the sender, but found the same high pressure with a mechanical gauge. They replaced the oil pump. Same result. They tore apart the engine, looked for a spun bearing, restricted oil path or anything else. They even brought in a rep from Mercruiser to look at it but couldn't find anything out of the ordinary. When they put it all back together, it still had the same high pressure. Merc said there isn't a high pressure spec, so not to worry about it.

Other than the high pressure, it's always run great, but I'm still leery that something could fail. I have one year left on the warranty, so I'll see how it goes this season. The good news is the warranty company covered the repairs even though a problem wasn't really found. Once the warranty is over, I'm likely to sell it just because I just feel a little uneasy about it.

 

[RidgeRunner]

Thanks for the reply-
"More is better" has to have a limit.
So I'm left poking around the harbor at 1500 rpm (55-60 psi) for fear of blowing something out...:smt021

 

[hottoddie]

Why not try a thinner weight oil such as 5-30. I'd also switch to a oil filter with a heavy gauge housing such as K&N.

 

[hottoddie]

Why not try a thinner weight oil such as 5-30. I'd also switch to a oil filter with a heavy gauge housing such as K&N. I've also seen a few cases of defective oil filters from Mercruiser causing both high and low oil pressure. Nothing special about MC filter other than the price. Personally I use K&N as both my rebuilt 454's have high output oil pumps.

 

[Lazy Daze]

You're fine. Go boating. You're good to go with your oil and filter. It's higher than what most will see, but it's not unheard of, either. You might find that it comes back down a bit in the Summer.

The big question... what was different about before that first oil change to after? It seems pretty clear that whatever changed there is the missing link in the equation. But again, just go boating! 70 is nothing, AT ALL, to worry about. It could be as simple as the pressure sender (sensor) being a bit flaky.

EDIT: When you say "verified with analog gauge"... are you referring to the dash gauge? That is a dummy gauge - it reads whatever the Smartcraft tells it to. To verify, correctly, temporarily install a mechanical gauge at the engine.

 

[Steve195]

Thanks for the reply-
"More is better" has to have a limit.
So I'm left poking around the harbor at 1500 rpm (55-60 psi) for fear of blowing something out...:smt021

I sort of feel the same way, but I have probably 20 hours on it since I noticed the issue and I've been running it normally, so I'm just going to keep treating it like I always have. The warranty does give me some piece of mind though in case something does go wrong.

 

[RidgeRunner]

Thanks for the piece of mind.
By "verified" I mean I plumbed in a Stuart-Warner ANALOG gage, tee'd off the block to incorporate the orig,. sensor and dash gage. BOTH read the same pressure. I'm going to permanently install the S/W gage, while still having the dash mounted one. (Having line made to reach the front of motor, I fab'd an Alum bracket for mounting-gage face should be visible with hatch open. Obviously, that Still that doesn't change the pressure.
BUT, I AGREE, what's happened since the oil change ????
I rechanged the 'new' oil, replaced the 'new' filter with a larger capacity version. Re-verified oil level. Replaced PCV-. Same. the ONLY variable would be the WEIGHT of the previously used oil. I've replaced everything except for putting back in the old oil!! I didn't do the 1st oil chance, so I don't know. Lastly, I'm hesitant to stray away from the recommended oil weight.
Thanks again for all who chime in-RR

You're fine. Go boating. You're good to go with your oil and filter. It's higher than what most will see, but it's not unheard of, either. You might find that it comes back down a bit in the Summer.

The big question... what was different about before that first oil change to after? It seems pretty clear that whatever changed there is the missing link in the equation. But again, just go boating! 70 is nothing, AT ALL, to worry about. It could be as simple as the pressure sender (sensor) being a bit flaky.

EDIT: When you say "verified with analog gauge"... are you referring to the dash gauge? That is a dummy gauge - it reads whatever the Smartcraft tells it to. To verify, correctly, temporarily install a mechanical gauge at the engine.

 

[Ozshadow]

My 7.4 MPI does that from launch (with new oil/filter) but as mentioned, slowly comes down throughout the season. I use 40w Rotella and only boat above 50 degrees. Higher oil pressure is typically a good thing.

 

[Lazy Daze]

BUT, I AGREE, what's happened since the oil change ????

Maybe the question that should be asked is, "What oil was originally in there that caused a lower PSI?"

 

[JVM225]

I would stick with the 25W40 oil. A high reading usually indicates a clog someplace.
If you haven't swapped out the filter, then try that. A clog in the filter could cause a high reading.
If you've changed the filter and still have the same reading then the next easiest thing to do is use one of those over the counter oil flush products you can buy in most auto parts stores and big box stores that sell those kinds of things in their automotive additives aisle.
They're cheap and easy enough to use. Usually you pour the contents of the bottle in the oil, run the engine for a specified period of time (5 or 10 minutes) at a prescribed RPM range, change the oil and filter and you're done.

 

[Thornton69]

How far above 70 are you going? Has your operating temp dropped? Is this boat new to you?
If it was mine, I would be concerned with the unnecessary additional strain being put on the pump drive and cam gears.
I would consider trying 15/40 or even a 10/30 if required to get it in the recommended operating range.

 

[fwebster]

The only concern I see here is that the 7.4 engine uses a gravity return oil system. The oil leaves the pump, goes thru the lower bearings first then thru the cam bearings then exits the oil system into the head and uses a splash system for oiling t he rocker arms. From there is collects in the head and run down drain holes back to the oil pan. If the holes aren't large enough to handle all the oil 70 psi delivers to the top of the engine, the oil just pools under the valve cover. The risk is that the oil pick up in the pan may not pick up the reduced oil level because the oil is in the valve covers. The usual indication of this occurring is burning oil and blue smoke because the valve guides are under the oil level collected in the valve covers and fluctuating oil pressure at high rpms.

I ran a pair of 7.4's for 9 years with 65 psi oil pressure at cruise .......from day 1 (w/125 hours on the engines) to the day I sold her 950 hours later. The high oil pressure was a concern for the mechanics at the marina but none of us knew what to do other than watch it. While the above scenerio is a potential effect of too much oil pressure, it is highly unlikely. So, watch for oil burning and fluctuating oil pressure at cruise speeds......go boating and have fun.

 

[johngus]

what happens after hot.my small blocks will be 60-80 on the gauge when cold but after a decent cruise and oil hot/thinned out will be around 45-50 3000rpm to about 20 at 600 rpm's.at 70 I would be happy,sounds like a healthy engine with tight clearances.though I do run straight 40W as recommended in the owners manual from 1988.

 

[techmitch]

The only concern I see here is that the 7.4 engine uses a gravity return oil system. The oil leaves the pump, goes thru the lower bearings first then thru the cam bearings then exits the oil system into the head and uses a splash system for oiling t he rocker arms. From there is collects in the head and run down drain holes back to the oil pan. If the holes aren't large enough to handle all the oil 70 psi delivers to the top of the engine, the oil just poplyols under the valve cover. The risk is that the oil pick up in the pan may not pick up the reduced oil level because the oil is in the valve covers. The usual indication of this occurring is burning oil and blue smoke because the valve guides are under the oil level collected in the valve covers and fluctuating oil pressure at high rpms.

Tired, reply ASAP.

I ran a pair of 7.4's for 9 years with 65 psi oil pressure at cruise .......from day 1 (w/125 hours on the engines) to the day I sold her 950 hours later. The high oil pressure was a concern for the mechanics at the marina but none of us knew what to do other than watch it. While the above scenerio is a potential effect of too much oil pressure, it is highly unlikely. So, watch for oil burning and fluctuating oil pressure at cruise speeds......go boating and have fun.

Tired, reply ASAP.

 

[Thornton69]

The only concern I see here is that the 7.4 engine uses a gravity return oil system. The oil leaves the pump, goes thru the lower bearings first then thru the cam bearings then exits the oil system into the head and uses a splash system for oiling t he rocker arms. From there is collects in the head and run down drain holes back to the oil pan. If the holes aren't large enough to handle all the oil 70 psi delivers to the top of the engine, the oil just pools under the valve cover. The risk is that the oil pick up in the pan may not pick up the reduced oil level because the oil is in the valve covers. The usual indication of this occurring is burning oil and blue smoke because the valve guides are under the oil level collected in the valve covers and fluctuating oil pressure at high rpms.

I ran a pair of 7.4's for 9 years with 65 psi oil pressure at cruise .......from day 1 (w/125 hours on the engines) to the day I sold her 950 hours later. The high oil pressure was a concern for the mechanics at the marina but none of us knew what to do other than watch it. While the above scenerio is a potential effect of too much oil pressure, it is highly unlikely. So, watch for oil burning and fluctuating oil pressure at cruise speeds......go boating and have fun.

Not trying to argue with what you are saying nor what you have found with your engines. The real concern for the OP is why was there a sudden rise in oil pressure. Only 2 things can cause a rise in pressure. Unless the tolerances have been reduced (which is worse case), the oil has got thicker (by viscosity or temp) or the volume of flow has gotten greater. The only way the flow can increase is if the regulator (relief) is stuck. There is no advantage to running higher pressures. It unnecessarily adds load to the pump drive and can increase the possibility of a failure with it and even the lube filter as someone else brought up. If the viscosity is too high, then the time it takes the oil (and pressure) to reach the top end is also increased during cold startups.

 

[boatman37]

Have to agree with the higher pressure/volume comment. When I raced and built my engines I absolutely would not use high volume pumps. Too much torque required to spin them. I have heard of 3/8" drills being burned up trying to prime a high volume pump. There are high pressure pumps available but they seemed to be a little higher pressure than I needed so I would buy a stock pump and remove the spring and insert a small washer to help stiffen the spring.

A little off topic but just to explain the negative effects of too high of pressure or volume.

Did you change brands of filters? Some filters have a check valve to avoid drain back. It is possible this valve may have malfunctioned. Probably not extremely likely but cheap and easy enough to replace to see if it may be the problem.