1993 Mercruiser 4.3LX - Dies in Water then Won't Start

[mtsumedi]

Okay, I was test driving a boat and while we were out the motor suddenly shut down. When we tried to start it back it turned over very sluggishly and in some cases it wouldn't turn over at all. After trying to get it to start for a minute or so there was some smoke coming out of the carb. We ended up getting towed back in and I used it to negotiate a lower price.

A couple hours later that same evening, I went out to the boat and it started right up and hums like nothing is wrong.

The guy told me that it had done this to him once before. He said someone told him was a timing issue possibly.

Anyone have any insight?

 

[CaptainMak]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

I'd pull the plugs first to see if there's water in cylinders.
How's the engine oil lookin' like ?

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

I'd pull the plugs first to see if there's water in cylinders.
How's the engine oil lookin' like ?

Nice and clean. Not milky at all.

 

[81 Checkmate]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Did you happen to remember what the temp gauge said?

Were you at idle or WOT?

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

I was back by the motor when it happened and didn't even think to check the gauge but the engine was not hot at all when i was investigating it.

 

[CaptainMak]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Nice and clean. Not milky at all.

Did you see if there's water/oil or both in the cylinders ? I know it's possible to hydrolock the motor with water OR oil.
I'd still pull the plugs and inspect.

The other thing that comes to mind is possibly a faulty coil. When they heat up (while running), the bad ones lose their ability to throw a good spark. Once cooled down, they work good again. Search YouTube for videos showing how to test an ignition coil. Hope this is the problem, not the block. :cold:

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

I certainly hope it's something as simple as the ignition coil but do you think that would cause it to turn over slowly after it shut down??

 

[alldodge]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

For the engine to shut down and then have difficulty turning over, I don't see this as an ignition issue. As previously mentione I recommend pulling all plugs

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Now, I've had it running a few times (all short 10 second or less durations) since it shut down. Will I be able to tell something from the plugs as it sits or do I need to recreate the shut down and then pull the plugs. I almost feel like if there was any moisture or residual oil in the cylinders it would have been cooked out by now.

 

[alldodge]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Now, I've had it running a few times (all short 10 second or less durations) since it shut down. Will I be able to tell something from the plugs as it sits or do I need to recreate the shut down and then pull the plugs. I almost feel like if there was any moisture or residual oil in the cylinders it would have been cooked out by now.

Why just 10 seconds or less? I'm thinking you would see some water.

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

10 seconds or less because it was not on the muffs.

Okay, would being able to turn the distributor easily by hand possibly cause this problem?? Lol

 

[alldodge]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

10 seconds or less because it was not on the muffs.

Okay, would being able to turn the distributor easily by hand possibly cause this problem?? Lol

You burned up the impeller, needs replacing now

If you can move the distributor without loosing the bolt, yes that could cause the issue.

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

It is a new to me used boat so the plan was always to change the impeller out.

 

[Maclin]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

For future reference, even if an impeller change is planned do not run it without water, or go thru the motions and take the impeller out. Running dry can be cumulative, like for the impeller vanes. Even running a short time dry can break pieces of the vanes off, and those lay in wait until water flow is present then go as far as they can then stop and probably clog a passage.

 

[CaptainMak]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

one thing to remember is never to do things half-***. If you cut corners or too lazy to do it the right way the first time, you'll have sime big expenses ahead.

get the engine to the point where it shuts off, pull out all the plugs at once, then crank again. see if any water or oil comes out of the plug holes.


Also, I'd suggest adjusting the timing and tightening down the distributor clamp

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

one thing to remember is never to do things half-***. If you cut corners or too lazy to do it the right way the first time, you'll have sime big expenses ahead.

get the engine to the point where it shuts off, pull out all the plugs at once, then crank again. see if any water or oil comes out of the plug holes.


Also, I'd suggest adjusting the timing and tightening down the distributor clamp

Who said anything about doing something half-***? I'm a little confused as to why this comment came about.

My thoughts were to do the exact thing you just mentioned. Run it until it shuts down then start digging into it.

 

[CaptainMak]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Who said anything about doing something half-***? I'm a little confused as to why this comment came about.

My thoughts were to do the exact thing you just mentioned. Run it until it shuts down then start digging into it.

Just the first thing that came to mind when you stated you ran the thing without muffs... but if you were to change it anyways, it's your call.
I learned this the hard way too.

 

[mtsumedi]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Update:

Finally got some time to mess with this thing today and here's what happened. I hooked the muffs up and got it running. I took the timing light out and got it set up. Let the engine run until it got up to normal (About 160-170) operating temperature. Set the timing to 8 degrees before tdc. It was running and idling fine at that point for a few more minutes and then it started running a little off. Not really rough just off and I started to smell fuel and see a small bit of smoke from the carb. I let it run until it shut down and it did the same thing as it did the day we ran it on the water. Wouldn't hardly turn over after that.

I pulled all the plugs and saw nothing "wet" on them. No fuel or water to be seen. The cylinders appear to have a fuel smell but no actual wet fuel in them. I turned it over for about 5 seconds after I pulled them all and looked and felt for moisture and nothing.

Here are pics of the plugs:

From left to right is 5, 3, & 1.


From left to right is 2, 4, & 6.


Does anyone know what my next step should be?

 

[Bondo]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

Update:

Finally got some time to mess with this thing today and here's what happened. I hooked the muffs up and got it running. I took the timing light out and got it set up. Let the engine run until it got up to normal (About 160-170) operating temperature. Set the timing to 8 degrees before tdc. It was running and idling fine at that point for a few more minutes and then it started running a little off. Not really rough just off and I started to smell fuel and see a small bit of smoke from the carb. I let it run until it shut down and it did the same thing as it did the day we ran it on the water. Wouldn't hardly turn over after that.

I pulled all the plugs and saw nothing "wet" on them. No fuel or water to be seen. The cylinders appear to have a fuel smell but no actual wet fuel in them. I turned it over for about 5 seconds after I pulled them all and looked and felt for moisture and nothing.

Here are pics of the plugs:



Does anyone know what my next step should be?

Ayuh,.... Right Then, at That point, when it Stalled,....

Was there power to the (+) terminal of the coil,..??
Were the spark plugs, Sparkin',..??

Was there visible gas in the carb,..??

The plugs look like it's runnin' Rich,...

 

[dingdongs]

Re: 1993 Mercruiser 4.3LX - Dies in Water then Won't Start

compression test the cylinders as valves may not be closing giving your symptoms.