4.3 L Mercruiser stalls repeatedly

[scoathy]

I just purchased a 2000 Q3 Tahoe a few weeks ago and after replacing the p/s pump yesterday at the shop I took it out for a spin. My daughter and I were on the water for about 30 minutes when it just died. We were at 3/4 throttle and the motor just shut down. I thought I had hit the kill switch but after verifying that and restarting, the motor died again after about 10 seconds underway. This went on for 45 minutes while I worked us back to the landing. I have had the boat out only a handful of times in the past month but never this problem.

The motor would simply shut down. Whether I let it sit longer or shorter before restart it did not matter, it might push me slowly for 20 seconds or fast for 30 seconds but the end result was the same...

I aslo noticed today that my temp gauge is no longer functioning after getting it back from the shop. I should be able to figure that out tomorrow though.

Any thoughts on the irregular shutdown? Do I need to give more info to help the forum help me?

2000 Tahoe Q3
4.3L I/O carb mercruiser
opening the engine compartment I never noticed any excessive heat but we were smelling a lot of gas fumes it seemed. It almost seemed as if the motor was flooding out but then would start right back up after it sat for 30 seconds to a minute and run a little bit... any help is greatly appreciated. I just bought this boat and already have invested more money than I had hoped into just making it reliable only to find that once again it is not. Getting closer though!

 

[Haut Medoc]

Re: 4.3 L Mercruiser stalls repeatedly

Try this.....
Fuel pump will run with the key in the 'start' position, but only will pump in the 'run' position if the oil preesure switch is operating.......
It is a safety feature.....
Hope this is your problem as it is an easy fix.....
Re: V8 Cutting Out​

You have an electric fuel pump. The oil pressure switch that gives power to the pump when it's running may be bad, or the connections are loose or corroded. The switch is located above the engine mounted oil filter boss.
You can jump the 2 wires together with a jumper and see if the pump runs when the ign. switch is in the run position.

Pic courtesy of Don S.....
__________________

 

[scoathy]

Re: 4.3 L Mercruiser stalls repeatedly

I jumped the wires together and the fuel pump kicked on... started pumping out too since I had earlier disconnected the fuel line to the carb to verify the little filter...Ooops!

I noticed the connector for the purple wire (located on the bottom side of the pressure switch) is full of oil. The bottom side of the entire switch had a nice little coating of oil for that matter... when I cleaned out the connector and reconnected the switch the fuel pump did not make any noise at all. Should I have heard something when I switched the motor on if the oil pressure switch is good?

You mentioned it would run but no pump with ign. in the start position so I guess my next question is will the fuel pump make any noise when running but not pumping?

Thanks!

scott

 

[Haut Medoc]

Re: 4.3 L Mercruiser stalls repeatedly

I jumped the wires together and the fuel pump kicked on... started pumping out too since I had earlier disconnected the fuel line to the carb to verify the little filter...Ooops!

I noticed the connector for the purple wire (located on the bottom side of the pressure switch) is full of oil. The bottom side of the entire switch had a nice little coating of oil for that matter... when I cleaned out the connector and reconnected the switch the fuel pump did not make any noise at all. Should I have heard something when I switched the motor on if the oil pressure switch is good?

You mentioned it would run but no pump with ign. in the start position so I guess my next question is will the fuel pump make any noise when running but not pumping?

Thanks!

scott

You read it wrong.....
The pump will work when the key is in the 'start' position.....
That's how you got back to the dock.....
But it wiil not run in the ''run' position if the switch is faulty.....
Now, the question is:......
When you jump the switch will the engine stay running ?......
If it will, you've located the problem.....

 

[scoathy]

Re: 4.3 L Mercruiser stalls repeatedly

Ahaa! Gotcha. Pump runs on voltage from the starter at startup and from pressure switch at some point afterwards.

Now let me ask you this. Could the switch work for a while until the engine gets to a certain temperature? The reason I ask is because we had to run the motor for quite some time this morning to get it to duplicate. Once it started though we had no problem duplicating.

I understand how to complete my troubleshooting on the pressure switch now I believe.

I will post the results later on.

Thanks for your time!

Scott

 

[Don S]

Re: 4.3 L Mercruiser stalls repeatedly

Anything is possible, after you get it to quit check both sides of the switch with a meter and find out for sure. After it warms up and the engine dies, start it up and check the voltage on the terminals with the engine running (you have about 15 to 20 seconds)

 

[scoathy]

Re: 4.3 L Mercruiser stalls repeatedly

Hey Don,

I believe I have a different problem... when I started it up it ran for less than a minute and then shut off. I restarted and before I could even jump the wires it shut down. Tried that several times and got to the point that it would not even start...

With the amount of oil on the pressure switch there is certainly something wrong there so I will replace the switch anyway I believe but not sure where to go from here. Maybe I will replace the big fuel filter when I swap the pressure switch on Monday and see what ahppens. The repair guy I went to this morning believes it is the carburetor but I am not sure about that as the boat ran fine the past 3 weekends for several hours and was running fine yesterday up to the point it shutoff...

I gotta start reading up on this motor so I can be a little more knowledgeable than I am at present.

Hell I can't even find the serial number for the motor... the flame suppressor is not the original and not sure how to get down to the starter to find the serial number down there...hehehe

Thanks for all your help Don!

Scott

 

[Don S]

Re: 4.3 L Mercruiser stalls repeatedly

Just jump the wires on the switch and see if it keeps running. If it does, the switch is bad. If not, you have other issues.

not sure how to get down to the starter to find the serial number down there...hehehe

Mirrors and flashlights and patience.

 

[scoathy]

Re: 4.3 L Mercruiser stalls repeatedly

Patience...hehehe...gotta remember patience...