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Marvin Gardens

oil pressure

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Marvin Gardens

I have a 1991 Malibu Sunsetter 201 with rebuilt 350. What should oil pressure be when cruising at 3000 rpm, 30 mph?

Thanks

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Woodski

Approximately 45-50 psi.

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Marvin Gardens

If I am low on oil will pressure be down that low, or is there another problem?

Approximately 45-50 psi.

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Marvin Gardens

Cruing back to marina at 30 rpm and 30 mph oil pressure dropped to a little under 20 psi and low oil light came on. I had to leave right away and did not have time to wait to check oil level in slip. Would the pressure be low just because oil level was low?

Approximately 45-50 psi.

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Marvin Gardens

I found alittle brass fitting in bilge. Not the 1 at the end of the oil drain hose. Any ideas?

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JasonK

Could be a drain plug. A new one would be used if the old one was lost in the bildge.

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Marvin Gardens

could the low oil pressure and the presence of oil in the bilge be due to a leak in the oil line leading to the gauge? get oil pressure gauge kit and replace?

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electricjohn

The oil pressure gauge is an electrical type gauge getting its signal from a sender threaded into the motor. Unless someone changed it to a direct pressure reading gauge.

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Marvin Gardens

thanks. if pressure dropped to 18-20 psi would i notice difference in performance? she ran strong back in to marina at 30 rpm, 30 mph, at that pressure for about 10-15 minutes

The oil pressure gauge is an electrical type gauge getting its signal from a sender threaded into the motor. Unless someone changed it to a direct pressure reading gauge.

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Marvin Gardens

i'll check oil level friday night, add to full, take out and see how pressure reads.

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wanttoski

Is there too high of a pressure? Sunday mine was running 60-80

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wienrdog

Is there oil in the bilge too? Your first post didn't mention it.

If not obvious oil leak, low oil pressure could be because of low oil level. If there's oil in the bilge, then it could be because of a leak somewhere letting the pressure drop.

You would not likely notice a difference in performance while you have a reasonable oil pressure, but it is something you need to be pretty careful about.

If it's not oiling well, it will likely run OK right up until you need a new motor.

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Marvin Gardens

yes, there is oil in the bilge.

there is only 1 season on rebuild of engine

Is there oil in the bilge too? Your first post didn't mention it.

If not obvious oil leak, low oil pressure could be because of low oil level. If there's oil in the bilge, then it could be because of a leak somewhere letting the pressure drop.

You would not likely notice a difference in performance while you have a reasonable oil pressure, but it is something you need to be pretty careful about.

If it's not oiling well, it will likely run OK right up until you need a new motor.

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Sixball

My oil pressure sits at 52 psi @ idle and 62 psi running above 1800 rpm. This will very some with temp but only 2 to 4 psi other then very cold like near freezing. What grade oil are you using?

20 /50? Under 20 psi is not good. You need to verify the gage and sending unit are correct. If so you need to look deeper. They always run good just be for they go Blowup.gif If you want to do a dirty Little check pull your oil filter and open it up look for any metal or Foreign substance. check the color of your oil. Not brown or milky? drain the oil do a oil change feel the used oil any particles run it through a fine cloth no metal I hope. If it is truly running as low as indicated you are going to have trouble.

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Marvin Gardens

Checked oil level as soon as I got to marina Friday evening. Oil barely touching tip of dipstick. I added to "full" and fired her up. oil pressure went right to 40+ psi. Cruised around for while and she maintained 40-50 psi entire time. Moderate use of boat all day Saturday, oil pressure never dropped, low oil light never came on. Sunday morning I checked oil level and it was a bit down. Looking carefully all around engine it appears as though the leak is at the sending unit. At first glance I thought it might be distributor shaft, but closer inspection, some cleaning of all areas, some more engine run time, and I feel confident it is sending unit leaking. I took it off and will replace with new 1 this Friday night. Hope that's all it was. Thanks very much for all of your help and input. Give me thoughts if you think/don't think sending unit is sole culprit.

Thanks

Gary

Edited by Marvin Gardens

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wienrdog

Glad you found it & that it was a relatively inexpensive fix!

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EZSnow

Glad you seem to have found the problem. To add a little information to the thread, you generally want to see 10psi of oil pressure for each 1,000rpm of engine speed.

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Marvin Gardens

went to a few auto parts stores after work and could not find exact sending unit. 1 that was same size and had same diamteter threaded stud on the engine side of unit had a different top end. 1 i took off had a small threaded stud that took small nut. this 1 has an end for a slide on clip. i guess i can still use it and cut/strip wire, crimp on clip and fit onto end of unit. any difference?

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electricjohn

No difference. Same ohms at same pressures. I went with a Mercruiser sender, has the same electrical connection as the original.

Edited by electricjohn

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