Low oil pressure question

majoma

Member
Oct 10, 2008
284
San Francisco
Boat Info
2000 340, V drive
Engines
Twin 7.4
On my 2000 340 with Mercruiser 7.4s, the oil pressure never gets higher than 35 psi on both engines. Although Mercruiser specs say that the pressure should be between 30 and 70, I am very concerned. Does anyone know what could be the possible cause of low oil pressure?
On my old Sea Ray the pressure always was between 50 and 60 psi.
Thanks
 
My 1997 7.4's usually hang around 40psi. They go up a bit when on plane but never to 70 psi.
 
The sender and gauge aren't that accurate either. Are the rockers making a clatter ? Usually the first parts to suffer if in fact your pressure is low
 
Check the wiring to be sure everything is tight / grounded. If both engines are the same I would lean toward there is not a problem. If you want to be certain put a manual gauge on it.

Also, what oil are you using? Oil pressure will be different with different viscosity oils.
 
If it's been the same for a while and the engines sound and run good, I wouldn't worry about. Gauges are best used for tracking trends, not actual numbers.
 
Thanks, You made me feel better. Just to make sure, I am going to have a mechanic verify the pressure with a mechanical gage.
 
Just repowered both dyno sheets said motors in the 50’s at cruise..... reinstalled motors gauges never read above 40
 
C26BB3DF-3111-4D22-AB83-EDA4B1CB052D.jpeg
 
I wish I had that in real time on my boat that’s the engine Dyno data from when my motors were rebuilt at the shop... lol

Great display. Which software would give you this type of data display?
 
My point was I know the engines are pumping at 50+ PSI but when we hooked up to the boat the analog gauges don’t really get any higher than 40 and usually hover between 35 and 40
 
I want to report an interesting finding. The oil pressure when I started the engines according to the electrical gages was about 30 psi at 1,500 RPM (which is the one they always read). The mechanic connected the manual gages and the pressure read about 40 psi at the same RPM. After that, he reconnected the electrical gages and the pressure now was about 40 psi on both engines. He could not explain why, after the test, the pressure went up from 30 to 40 psi at the same RPM.
 
[ sounds like corrosion to me something that I guess we all fight on our boats basically by disconnecting the connection on your oil pressure sending unit and hooking up his mechanical and then re-connecting everything cleaned up the bad connection



QUOTE="majoma, post: 982843, member: 5164"]I want to report an interesting finding. The oil pressure when I started the engines according to the electrical gages was about 30 psi at 1,500 RPM (which is the one they always read). The mechanic connected the manual gages and the pressure read about 40 psi at the same RPM. After that, he reconnected the electrical gages and the pressure now was about 40 psi on both engines. He could not explain why, after the test, the pressure went up from 30 to 40 psi at the same RPM.[/QUOTE]
 
Agree with Joey. The simplest answer is loose/dirty connections.

FYI, I meant to add this earlier... the 30-70 PSI you mentioned (in case you didn't know) is at 2,000RPM. The idle spec min is 4psi.
 
I don’t have my manual handy, but I had this concern at one point with the same engines.

I was really surprised at how low the spec range was compared to what I was thinking.
 

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