Oil pressure for mercury (GM 350) 260 hp alpha 1 drive

ernaldamerican · #1 July 26th, 2007, 01:02 PM

I have a 1985 chris craft and am assuming the motor is of the late 80's early 90's vintage. I have put an oil pressure gauge tee'd into the oil pressure sending unit line (up stream0. At idle I am getting around 60 psi for oil pressure.

What is the acceptable or normal range for oil pressure at idels for 350 motor?

Haut Medoc · #2 July 26th, 2007, 01:11 PM

Welcome to iboats.....

I would think it would be lower......
The min. psi is about 5......
The max should be 70 or so......
What is the PSI @ 2,000 RPM?........

Silvertip · #3 July 26th, 2007, 02:16 PM

60 PSI is not overly high on a "cold" engine. At idle, after fully warmed up it will typically be in 35 - 40 PSI range. After a hard run at WOT it may drop to 20 when returned to idle but it will gradually rise again after the engine has cooled a bit.

ernaldamerican · #4 July 26th, 2007, 02:53 PM

Thanks for the replies. I need to state that the gauge on the console will read 40 ish at idle (cold) but the gauge at the T I have back at the sending unit is reading 60 ish. I think it might be the a problem with gage at the T. i am going to take some numbers tonight (from both gages) at 1000 rpm intervals up to WOT, and then back at idel and reply back with those to see if any one thinks they are out of the normal range.

Again appreciate the advice.

tommays · #5 July 26th, 2007, 02:55 PM

what weight oil your useing and how warm it is will also have an affect on pressure

Tommays

ernaldamerican · #6 July 27th, 2007, 09:17 AM

All

I am using quicksilver 10w 40 motor oil. Took the boat out last night and have the follwoing data:

Initial start up on lake

RPM oil pressure

1200 (throttle in neutral) 45 psi
700 (throttle in fwd gear) 42 psi
1500 42 psi
2000 42 psi
2500 62 psi
3000 62 psi
3500 62 psi
4200 58 psi

WTO 4200 - 4300 rpm water temp 160 deg f, oil press. 58 psi

came back from WTO to 2500 rpm and oil pressure was 42 psi

came back to idle (throttle in fwd) and Oil pressure was 22 psi

tommays · #7 July 27th, 2007, 09:49 AM

I believe the quicksilver 10-40 is a 4 stroke outboard oil as merc recmonds there 25-40 or ST-30 ,ST-40 or ST-50 depending on temp where you boat

Tommays

ernaldamerican · #8 July 27th, 2007, 10:28 AM

My apolgies, I need to double check the oil viscosity. I got it from boat dealer for inbaord 4 stroke but could have grapped the wrong one. i will check.

ernaldamerican · #9 July 30th, 2007, 09:47 PM

Sorry for getting back so late. you were absolutely correct its 25w-40.

Do the pressures look correct for this weight of oil?