Low Oil Pressure..... safety/restrictor?????

[KetchiMan]

So, I just had my leaky oil pan replaced (cost over $1000 with the pulling of the the engine...) and now my oil pressure is low, like around 20.

Boat idled fine, putted around for a bit before giving her throttle. She came "almost-just-barely up on step" and the engine started sputtering. I idled her down and she sounded just fine, so I repeated the process. Same thing. Looked at the gauges and noticed that my oil pressure was low (...and temp gauge was completely dead). NO knocking/rattling noises or anything. This almost-on-step-sputtering-thing is EXACTLY what the engine did once before when it was legitimately low on oil (2 qts low... due to the leaky oil pan) and the engine had low oil pressure. Last time, I added 2 qts and the engine ran just fine. This time, the oil wasn't low, it was actually a bit high.

"Joe-expert" at the dock seemed to think that there is a safety mechanism that restricts the throttle when the oil pressure is low and says that if you have a bad pressure gauge/sending unit, it will restrict the throttle even if you have oil and good pressure. Anybody know if this is the case???? Could a simple sending unit/gauge issue cause this?


***More info.....

The oil is overfilled... could that cause the problem? It's about 1/2 inch above the "full" line on the dipstick. (For reference, there is about 1/2 inch between the full line and the add line)

It was filled with 10-30 (is that too thin???).

Also, my oil pressure gauge stays at 20 even when the key is turned off. Shouldn't it read zero with the key off???

Thanks

 

[mboudre1]

Re: Low Oil Pressure..... safety/restrictor?????

You have what is called an oil pressure switch. I will shut off power to the fuel pump if it detects that you have no oil pressure. Boat won't even start without oil pressure unless you bypass the switch. You can try a jumper cable to bypass the switch and start diagnosing by process of elimination. When was your last tune up, sounds like the engine is missing. IE.. spark plugs, wires, distributor....coil.....

 

[04fxdwgi]

Re: Low Oil Pressure..... safety/restrictor?????

Too much oil can make it so high that the cranckshaft will slop through it, causing the oil to foam up, which will show as low oil pressure. This usually shows up after running at a decent RPM for a while at temp.

Some gauges will stay at last known value when turned off, but it's not common. You stated your temp gauge is dead, too. I would be suspect of the 2 happening at the same time be begin looking for possible miswiring, since the engine was removed.


Sudden appearance of a misfire, dead temp gauge, flakey oil pressure gauge ????? I would concentrate especially on the possibility of a ground that didn't get connected correctly.

 

[achris]

Re: Low Oil Pressure..... safety/restrictor?????

How to Ask a Question.... Please Read This Before Posting A Question...

If the engine is an MPI, then yes, low oil pressure will bring 'Guardian' in, and restrict the amount of power available.

Chris.......

 

[mr300z87]

Re: Low Oil Pressure..... safety/restrictor?????

This sounds electrical. What does the oil pressure gauge read with ignition on but engine off. It should read 0 oil pressure. If it still read 20 I would start looking at that circuit. Coincidence that after engine removal gauges not functioning?

Mike

 

[Eric 3.7LX Alpha 1]

Re: Low Oil Pressure..... safety/restrictor?????

We need: Year of engine, size of engine, boat manufacture and length of boat is irrelevant.

Mercruiser used over 50-different engines thru the years.

 

[KetchiMan]

Re: Low Oil Pressure..... safety/restrictor?????

We need: Year of engine, size of engine, boat manufacture and length of boat is irrelevant.

Mercruiser used over 50-different engines thru the years.

Of course...
2004 Merc 5.0L MPI, serial # 0W018920 in a Trophy 2359

 

[Don S]

Re: Low Oil Pressure..... safety/restrictor?????

You have what is called an oil pressure switch. I will shut off power to the fuel pump if it detects that you have no oil pressure.

Not exactly. There is an oil pressure switch on carbed engines that keeps the fuel pumps from running with just the ignition key on and the engine not running.
The OP has an MPI engine and does not have that switch as the ECM controls the pump.

The oil pressure sender is showing no oil pressure will drop the rpm to idle or just above it.

Get the oil to the proper level and see how it runs. If the crankshaft is hitting the oil, it will areate the oil, and make it read low, but it also makes the lifters soft. Usually noisy as well.

As far as being 20psi on the gauge with the key off, doesn't matter, turn the key on and see what it says. Then there is power to it.