1995 Mercruiser 5.0 low oil pressure

[crawleym]

I have a 1995 Mercruiser 5.0 that I had stored in a garage over the winter. Where I live the temperature does not get to freezing so I did not winterize the boat and I store it in the garage. I had just acquired it used before the end of last season in August had had all the maintenance done on it at that time (new fluids, plugs, etc) and had the bellows replaced due to a loss of drive oil. The last time I had it out for a full run was at the end of October and I figured I ran it no more than 20 hours (I don't have a hour clock on the engine so this is an estimate). Since then I was turning it over every couple of months. I notice now that my oil pressure is not coming up until the engine warms up. I know the engine has the correct grade of oil since it was done by a reputable shop. I found the wire to the oil pressure sender. When reading low pressure, I connect and disconnet the wire, the needle on the gauge moves slightly.

Any thoughts on possible problems?

 

[Bt Doctur]

Re: 1995 Mercruiser 5.0 low oil pressure

Try grounding that wire and see if it goes full scale,
Yes, replace sender
No , check wiring to gauge, check gauge, check all grounds
remove sender, install a T fitting with a mech gauge to verify electrical one

 

[zbnutcase]

Re: 1995 Mercruiser 5.0 low oil pressure

The oil pump and drive setup on Chev engines is very reliable, could be a sender/gauge issue, the only way to really know is by connecting a mechanical guage to engine and run it. Chevs need bout 10psi per 1000 rpms of pressure to survive, at the minimum. 'nutcase

 

[Black as]

Re: 1995 Mercruiser 5.0 low oil pressure

I have a 1995 Mercruiser 5.0 that I had stored in a garage over the winter. Where I live the temperature does not get to freezing so I did not winterize the boat and I store it in the garage. I had just acquired it used before the end of last season in August had had all the maintenance done on it at that time (new fluids, plugs, etc) and had the bellows replaced due to a loss of drive oil. The last time I had it out for a full run was at the end of October and I figured I ran it no more than 20 hours (I don't have a hour clock on the engine so this is an estimate). Since then I was turning it over every couple of months. I notice now that my oil pressure is not coming up until the engine warms up. I know the engine has the correct grade of oil since it was done by a reputable shop. I found the wire to the oil pressure sender. When reading low pressure, I connect and disconnet the wire, the needle on the gauge moves slightly.

Any thoughts on possible problems?

Normally on start up the oil pressure starts high and when warm starts to drop, you may have a faulty oil pressure switch.

 

[crawleym]

Re: 1995 Mercruiser 5.0 low oil pressure

I understand the function of the Sender. What is the function of the Oil Pressure switch?

I believe I found both but they are not located where the Seloc manual said they would be. It said the sender would be on Starboard side above starter. It is on port side not too far from where the oil filter is mounted. I found it by finding the light blue wire.

I think I found the Oil Pressure switch by looking for the Tan/Blue wire. It is also close to the oil filter. But there are several other items that are connected to the Tan/Blue wire. What is the purpose of the Oil Pressure switch? What would/should happen if I disconnect it while the engine is running?

Also, thanks to all. I'm new to boating and these forums are really great!

 

[Don S]

Re: 1995 Mercruiser 5.0 low oil pressure

The oil pressure switch is just that a switch. On or OFF..
With typically oil pressure of 5-7 psi, the switch will turn off, which like a light switch opens the circuit. If the pressure drops belows that pressure the switch is closed and the alarm goes off.
The switch has NOTHING to do with the gauge.

I believe I found both but they are not located where the Seloc manual said they would be.

That is what you get for using knee pads for a manual. Go up to the adults only sticky at the top of this forum and download the proper OEM manual for your engine. Then you sand some kind of a chance of getting it fixed.