Lehman Oil Pressure

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Oct 19, 2007
Need some advice from you Lehman gurus:*

I have two SP135's with about 6300 hrs on them. Port engine oil pressure is 20 psi at 1500 rpm, starboard is 30 psi--both read at the engine mounted gage.

Engines run fine, don't use much oil, very little smoke at startup, and water temps are normal.

Is the low oil pressure a problem?
I have twin 80 hp Lehmans, I normally see about 40 psi.*Do your upper and lower helm instruments read the same?*
"Is the low oil pressure a problem?"

No way to know with out replacing the gage with a QUALITY mechanical gage AT the engine.

S-W has fine 270deg sweep gages that will tell the tale for about $50.

Temporarily install the gage , chart the oil pressure at start with cold oil and then again at various RPM's underway. The warm , cold difference is valuable information

A set of shooters head gear makes the Hell Hole more comfortable for the min spent reading the gage.
Electric "remote" gages are really only fancy IDIOT lights , not very accurate .

For accurate remote gages get Murphy Gages , which are mechanical.

When you have the numbers call Bob Smith , he may need to send you a crank , and rod bearing set.
Pressure is being measured by gauges at the engine--remote gauges agree with engine gauges. Had a mech check it and he verified 20 psi on one and 30 on the other, said they should both be 40 at idle although my operating manual says minimum of 30 psi.

He said problem could range from pressure regulator valves to weak oil pumps to major bearing wear. (Minor $$ to unlimited $$)

Oil is off to analysis--I'll keep you posted.

Thanks for the advice!

-- Edited by GeorgeW at 09:07, 2007-10-31
I installed mechanical gauges on my SP135's a couple of years ago just because i didn't trust the electric gauges. The good mechanical gauges on the engines both read about 45lbs at idle and 65 at 1800 rpm. The engines have about 2100 hours on them. Just for comparison.
I also have 135's with ~3000 hours.* They have 50 and 55 psi at 1900 rpm measured by mechanical gauges.
Thanks for the input, guys. Still awaiting analysis results. Meanwhile taking medical merlot to keep the nightmares under control!
I also have 135's with ~3000 hours.* They have 50 and 55 psi at 1900 rpm measured by mechanical gauges.
Is there an echo in here?*
Well, the verdict is in: nothing at all wrong with my 6300 hr Lehman 135SP's.
New oil pressure sensors properly*installed show 45-50 psi at the engines. A slight difference on pilothouse gauges but they're as old as the boat.*The oil analysis was clean.
Thanks to all for your help, and Happy Thanksgiving!
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