Fuel pump not getting voltage, low oil pressure?

[Dazzed]

Hey there, here's the situation. I recently replaced my cracked case 4.3l mercruiser 90-92 model, with a lightly used 100 hours quicksilver remanufactured 4.3l that came with an electric fuel pump.(1992) The boat starts up and runs great for about 3 minutes then shuts off. I've tested the oil pressure switch, and all the leads for continuity to the pump. Still no voltage to the pump. I've narrowed it down to the fact that I am not getting enough oil pressure to activate the oil pressure switch. The dash gauge isn't reading any pressure either. The oil and filter were changed just before I purchased it. I did notice the oil level was high on the dipstick. Can anyone chime in?

 

[alldodge]

Unplug the oil switch and jump across contacts which will keep the pump running and the motor.

Connect a mechanical gauge to either the oil switch port or the oil gauge port and see what pressure you actually have.

Hope you have a bad gauge and switch, otherwise you need to rebuild the motor

 

[Dazzed]

Ok I'll give that a try. What do you mean by rebuild the motor? That makes me nervous.

 

[Bt Doctur]

running a motor with no oil pressure destroys it, thats why you have to test with a mechanical gauge screwed in where the sender goes

 

[Dazzed]

Jumped the switch, motor runs great, fuel pump is running. Checked the oil pressure with a mechanical gauge and got no oil pressure whatsoever. What do I have in store?

 

[alldodge]

If there is oil showing on the dipstick and your sure its oil, then need to pull the motor. Either the oil sump has come off the pump, or the oil pump and/or bearings are gone. Need to rebuild or replace the motor.

Cheapest route is normally a truck motor out of a junk yard and change over stuff to marine type

 

[Bt Doctur]

Not poking a stick but exactly how did you go about checking it? wondering if it was installed in a blind hole

 

[Dazzed]

As you can see in the picture, the oil does come up a little ways along the pickup tube to the gauge. I installed it where the oil switch was, just above the oil filter.

 

[Bt Doctur]

 

[Dazzed]

That's the spot

 

[Bt Doctur]

pull the motor and drop the pan.replace the oil pump.IF and its a very big IF the bearings have not been damaged you could still have a viable motor by replacing the oil pump.Drop the pan, remove the oil pump body bolt and it drops down. Install a new one matching the tang to the dist bottom.

 

[Dazzed]

How is this even possible? I mean the motor only has 100 hours on it

 

[Scott Danforth]

Its man made....everything man mad will fail

 

[alldodge]

How is this even possible? I mean the motor only has 100 hours on it

Said it was replaced with a reman which had 100 hours, there was a problem with the motor when you bought it. Maybe this is why it was being sold

 

[Dazzed]

No doubt, another expensive lesson learned. I'll keep you guys posted and report back once I get it figured.
B.O.A.T. Bring out another thousand!

 

[Dazzed]

Turns out I have gas in the oil. I can smell it, and that would explain the high level reading on my dipstick and also low oil pressure. I wonder if I heavily flooded the motor trying to prime the fuel upon first start. I'm going to do an oil change today and see if I dodged a bullet.

 

[Fishermark]

Jumped the switch, motor runs great, fuel pump is running. Checked the oil pressure with a mechanical gauge and got no oil pressure whatsoever. What do I have in store?

No pressure whatsoever would not be from simply having gas in the oil. And there's no way you can have that much gas in the oil simply from flooding the engine trying to start it. If you truly do have "0" oil pressure, I would suspect the oil pickup has fallen off of the pump. When I rebuild an engine I usually tack weld the pickup onto the pump. Especially if it is the type that is simply a press fit.

 

[Scott Danforth]

I agree, I would still pull the motor to pull the pan, then spend $35 on a new pump and $10 on a new pickup

 

[alldodge]

Turns out I have gas in the oil. I can smell it, and that would explain the high level reading on my dipstick and also low oil pressure. I wonder if I heavily flooded the motor trying to prime the fuel upon first start. I'm going to do an oil change today and see if I dodged a bullet.

I doubt s the carb, and if it has a fuel pump mounted on the block, then thats the issue. I'll bet a beer that its the fuel pump has a ruptured diaphragm.

https://www.mercruiserparts.com/bam/subassembly/31478/951/90

 

[Fishermark]

I'll bet a beer that its the fuel pump has a ruptured diaphragm.

That was my first guess, but then remembered he said it has an electric fuel pump