Just finished up the install on my "New to Me" Yanmar 4LH-DTE engine. After a couple of trials on the local lake, I realized my oil pressure seemed high. I put in a mechanical gauge, and verified that it was idling hot at about 60 psi, and goes up to 80 when I surpass 1800 RPMs. I had changed the oil and filter while it was on the bench in my garage. I had put 15W40 in it and a factory oil filter. After seeing the high oil pressure, I put half a can of Seafoam in the oil, and ran it for about an hour a day 5 days in a row, then changed the oil to 10W30 and put a new oil filter in. The oil pressure is now about reading about 50 PSI hot idling, and now hits 80 at about 1900 rpms, so I saw a difference, but not enough to make me comfortable. Does anyone have any ideas what might be going on here? Does that oil pressure seem excessive to you? Thanks in advance.
What weight oil does yanmar call for vs your outside air temp? Do they have a oil pressure spec at certain rpm?
I am struggling to find a service manual with the required PSI specs, but the 10W30 I put in is what the operators manual calls for in this temperature
Boatdiesel.com has manuals for download i think it's $50 a year for a subscription well worth it to me. I didn't see any oil pressures range listed but they might have the manual your looking for.
Those numbers sounds fine to me. There is a service manual here. http://rhinomarineboats.com/PDF/4LHA-Service.Manual.pdf
Thanks for that Bach. This is for a 4LHA, not sure if it would be different than the 4LH that I have. I ordered one from TOAD supply. Should be here this week. I am starting to feel more comfortable with my numbers.
I believe when I took out my thermostat and tested it it was 162d thermostat and seemed to work properly in the pan
Finally got the factory service manual. It says 50 to 64 psi at max rpm. I hit 80 psi all the way from 1800 rpm to 2800 rpm, which indicates to me that the oil pressure control valve is functioning, just not set correctly either due to a shim, or possibly a stiffer spring. Problem is I can’t take it apart and look for a shim without pulling the engine
