engine starts, but stalls after 1 or 2 mins, just changed impeller

[pocoloco]

Hello all,

Have a 4.3LH 1998 Mercruiser I/O.
I just finished putting the outdrive back on the boat after having changed out the impeller/water pump. I also changed the U-joint bellow while I was at it.
As I went for a test run my engine had a little difficulty starting, when it did it ran for a minute or 2 before stalling and quitting. It was worse when I reved the engine up to say 2000-3000 rpm in neutral, Iwould keep it at say 2000rpm and it would then start dropping in rpm before it suddenly died.

I don't know if this could be related to the work I did in changing the impeller and seals. I have a manual I went by and the only thing I think I did differently is add a lot of grease to the gimbal bearing and u-joints, which were like new.

Could the problem I have with the engine stalling be something toptally different from the service work on the drive and how can I narrow down the problem. Just changed out the spark plugs. I am considering taking the outdrive off again to inspect it, although I am not confident this will solve ar halp anything...

Any advice would be appreciated.

 

[Don S]

Re: engine starts, but stalls after 1 or 2 mins, just changed impeller

Are you sure about the 1 or 2 minutes, or could it be 15 or 20 seconds. Big difference in the answer.

 

[pocoloco]

Re: engine starts, but stalls after 1 or 2 mins, just changed impeller

Hi Don,

Well, nope not sure on the time, it may even be 1/2 a min. You may however be insinuating checking a sensor or something. Oil pressure sensor perhaps? If so, how do you jumper the sensor out? Any other sensors I could jumper out?

Would you go back into the stern drive to see that all is OK?

cheers.

 

[Don S]

Re: engine starts, but stalls after 1 or 2 mins, just changed impeller

I doubt the stern drive work had anything to do with your problem.
What can happen since you have an electric fuel pump is the oil pressure switch or the wiring to it may be the problem.
When you start the engine, the pump gets it power from the starter which fills the carb. After the starter is released, you would have oil pressure and the switch would close putting ignition voltage to the pump. IF that doesn't happen, the engine will run till the carb is empty, usually 15 to 30 seconds I would guess.
The switch is usually located on a tee with the oil pressure sender or sometimes all by itself on the port/aft side of the engine below the exhaust manifold, and has 2 wires going to it.

 

[pocoloco]

Re: engine starts, but stalls after 1 or 2 mins, just changed impeller

so.... if I connect the 2 wires that lead to the pressure switch together, the engine should not stall on me, provided the pressure switch is the cause of the problem, right?

You can rule out that something is a little tight or binding in the drive that could stop the engine? I guess I am really looking for a connection here (& at the same time hoping that it is unrelated), because the week before I took the drive off, I had the boat in the water and the engine ran fine...

 

[pocoloco]

Re: engine starts, but stalls after 1 or 2 mins, just changed impeller

It turned out that I never knew what kept the engine from running. Once out of the water I retried the engine, took the clock to see how long before it shuts down... It took over 1 min, the second time it did't stop.
Put the boat in the water, no problems. Strange it would always stop on me the other day.
I figure I must have had bad fuel or much water in the fuel tank and it just took many starts until the engine ran smooth again. In any case, we're running good.
thanks for all ideas.