2007 RZ2 low oil pressure

[LalaRN]

We changed from the manufacturer recommended 5w-30 oil to straight 30 on advice from our Tige authorized mechanic. With a new pair of the "high capacity" oil filters we are only getting about 30 psi at 2500 RPM. That is much lower than when we put her away for the winter last year after installing new oil lines and we are trying to solve the mystery. In calling around we have had varying advice about how "full" of oil we should be running. Some say full and others say 3/4 full. I've been reading lots of posts this morning and see a lot of variation around the weight of oil. I've also read that we need to confirm the low pressure concerns with a mechanical gauge. I'd love to hear what type of oil and oil filters folks are running in their 2007 RZ2 400HP 6.0L Vortec engines. How full is ideal if we are trying to avoid starving the engine? Any other theories for where our pressure might have gone? One mechanic suggested that psi drops as the engine hours increase as a reflection of natural engine wear. I'd buy that except she was running between 45-60 last season. Thanks!

[gumby]

Filters can change the oil pressure. Oil weight can change pressure. I don't have this boat(2007 RZ2) Why did you make the change to this new pair of Filters? Are they OEM or were you trying to get some performance up grade? Also not sure why you wouldn't run the oil level full.(On the stick) Are you getting blow by? Dose the boat have excessive hours? Did you change from a single filter to duel filters?

[Jetdriver]

Are you sure he didn’t mean 30 weight in your drive? I’ve never heard of anyone running 30 weight in that engine. I would think the oil change could definitely be responsible for the pressure change.

[LalaRN]

Good Morning and thank you so much for responding! I meant that we had recently replaced the filters. The mechanic replaced a pair of high capacity filters with a new set so unless they aren’t equivalent that shouldn’t be a problem unless filters take time to wear in? No blow by that I know of. The engine compartment is oil free and the bilge water isn’t oily. Boat has about 340 hours.

[LalaRN]

Interesting! The advice was for the engine oil but I question it too because our owners manual says 5W-30 not straight 30. We just weren’t sure if the weight of the oil would have this kind of impact on psi. I saw some posts where tige owners were really experimenting with different weights. If our goal is to keep psi up should we go back to manufacturer specs? I don’t know what oil was in it last year when we had the good pressure...

[boatwakes]

Go back to 5w-30. The first number of an oil weight represents its cold flow properties and 5w flows quickly, necessary when feeding all the oil galleries inside the engine. The second number represents the oil's temperature protection rating. The 6.0 LS based marine engine is a solid workhorse with very tight internal clearances which require the use of a quality 5w-30. Use a semi-synthetic blend of your favorite brand and stay away from full synthetic oils unless using Amsoil. Recent discoveries using full synthetic oil has found the oil to completely fall away from cylinder walls and valve stems leading to extreme wear upon cold start up. The aviation industry discovered this recently due to several small aircraft engine failures.

Secondly, instal a temporary mechanical oil pressure gauge to check for actual pressure. Also, Marine Power is the only engine company using dual filtration mounts. GM found this to be a detriment to oil flow and has a TSB on it somewhere I need to pull up for you all. Basically, there are several issues you need to address but start with changing the oil back to factory recommended, change the filters and then check for accurate oil pressure with a mechanical gauge. Keep in mind, idle oil pressure will fall with its temperature rise so if your oil is 150* or more, it will be much less at idle than when its cold.

[LalaRN]

Will do. Studying now about semi-synthetics. We CLEARLY have not paid enough attention to the type and quality of oil we are running. Lesson learned! Thanks so much!

[LalaRN]

Hi All,
We got the mechanical oil pressure gauge installed as advised. The oil pressure on that gauge matches the dash. The advice we have over the phone from our Tige mechanic is that we need a new engine either due to bad bearings or internal oil leak. No smoke in the exhaust and the engine sounds like it is running perfectly. No banging or hammering. Any other ideas from this group less extreme than a new engine. If folks agree we need a new engine, thoughts on rebuilt versus new? Remember that this engine has 340 hours on it and was running perfectly at the end of last season.