Merc 4.3 oil leak from sensor?

[Nucklez]

I've noticed a oil leak coming from a sensor on the port side of my Merc 4.3. The boat is from 1996, but the engine isn't the original. I'm just curious if you guys know what this sensor is? I've heard it could be the oil sending unit, or possibly a sensor for it. I've been looking for it in the service manual without any luck yet, but I'll keep trying. If you guys know what this thing is, that would be great. The leak is coming from around the black/yellow wire. Thanks for your help!

 

[Don S]

Re: Merc 4.3 oil leak from sensor?

It's the oil pressure switch for fuel pump control.

PN 87-805605A1

 

[Nucklez]

Re: Merc 4.3 oil leak from sensor?

Great! I imagine that just butts up against some fresh oil then and leaking through a bad rubber seal. So, draining the oil from the engine and replacing that switch should be all I should be concerned with I'd imagine. Thanks for the quick response!

 

[achris]

Re: Merc 4.3 oil leak from sensor?

You don't need to drain the oil. That switch is in a gallery, so only sees any pressure when the engine's running. One thing I did notice, it looks like those exhaust manifolds are the notorious 'batwing' single piece units. If you love your engine, toss 'em... Convert to 2 piece, preferably dry-joint.

Chris......

 

[Nucklez]

Re: Merc 4.3 oil leak from sensor?

You don't need to drain the oil. That switch is in a gallery, so only sees any pressure when the engine's running. One thing I did notice, it looks like those exhaust manifolds are the notorious 'batwing' single piece units. If you love your engine, toss 'em... Convert to 2 piece, preferably dry-joint.

Chris......

Wow, good eye there! I did not know about the bat wings, I did think they looked cool though. I just got the boat about two weeks ago, and have dove in strong. Thanks for the info, and I'll dig it all up. Thanks for your help!

 

[Don S]

Re: Merc 4.3 oil leak from sensor?

You don't need to drain the oil. That switch is in a gallery, so only sees any pressure when the engine's running. One thing I did notice, it looks like those exhaust manifolds are the notorious 'batwing' single piece units. If you love your engine, toss 'em... Convert to 2 piece, preferably dry-joint.

Chris......

If he boats in fresh water only, it's not a big deal. Those manifolds will last for years in fresh water.
I've pulled elbows off boats that are 25 years old and they look like new in the water passages. If he was in salt water, they would have already killed his engine.

 

[Nucklez]

Re: Merc 4.3 oil leak from sensor?

Yea, I only boat in fresh water. I was looking at the sensor last night. My original thought was that oil was coming out of the wires, that doesn't seem very possible. I couldn't crank it because my ears are missing. I looked everywhere! I've come to the conclusion that my newbie experience self left them on the foot when I left for the lake and they fell off on the way. I'll stop by and pick some up soon, I really need another pair. It really looked like the oil was coming out that hole in the plug around the wire. Only thing that appears to be able to "drip" on it would be the valve cover, or heaven forbid a possible head gasket. I'll update what I can when I get to crank it again. Thanks for everything guys!

 

[FishHog]

Re: Merc 4.3 oil leak from sensor?

I pulled my batwings off my 99' last year, and from what I saw I was glad I did. that was all freshwater boating. they might be fine, but probably worth pulling them and having a peak.

 

[BRG25]

Re: Merc 4.3 oil leak from sensor?

If he boats in fresh water only, it's not a big deal. Those manifolds will last for years in fresh water.
I've pulled elbows off boats that are 25 years old and they look like new in the water passages. If he was in salt water, they would have already killed his engine.

Don...that is contrary to advise you have given in other posts...like this one...

http://forums.iboats.com/mercruiser...-3l-exhaust-manifolds-intake-both-573310.html

My engine is a 1998 and I boat in fresh water. I replaced my 1-piece exhaust manifolds last year because a big chunk of metal came out of the exhaust when we pulled the drive. I personally think you are rolling the dice...

 

[Nucklez]

Re: Merc 4.3 oil leak from sensor?

Back on topic, That sensor really was leaking oil out of one of the wire prongs. My local marine shop had the Mercruiser replacement part, which includes a plug with new wires to connect to the existing wires. It's part number 87-864252A01. The oil pressure safety switch. No more oil leak at all! I felt like Exxon Valdez when I ran my bilge from time to time. I'm glad that's taken care of. Thanks guys, and I'll check on those bat wings.