4.3 Mercruiser submerged - Perplexing problem

[Alabamangler]

Boat Background:
2018 Chaparral H20 Sport with 4.3 Mercruiser MPI ECT with 36 hours
The rear of the boat was partially submerged in fresh water for approximately 12 hours in December 2022. It was immediately taken in for service where the following steps were taken, and parts were replaced:

1. Oil and Filter
2. Starter
3. Alternator
4. Distributor Cap

The boat cranked and ran with muffs. We then took it for a water test where it cranked, ran, but then quickly stalled out. It may be coincidental, but the motor stalled when I attempted to trim the motor down. At this point, the starter would engage, but it would not crank or run.

At this point, I did the following:

1. Installed new batteries (2 x Deka Marine Master 27 series Deep Cycles)
2. Replaced fuses
3. Drained the gas tank
4. Replaced the fuel filter
5. Refilled with 20 gallons of non-ethanol fuel

Note, that during this time, the boat would not take fuel well from the gas pump and would overflow easily. There was also water coming out of the vent line during fueling. I found that the carbon filter was saturated with water and was hoping it was the culprit causing fuel starvation. I disconnected it temporarily to test.

While testing, I noticed the battery draining excessively after 1-2 starting attempts, and it appeared that there was not enough power to turn the starter. Now, the starter will not engage at all, even with a full charge on the batteries.

I'm absolutely perplexed at this point and have taken it to another dealer. Any advice or ideas are welcome.

 

[Scott06]

Boat Background:
2018 Chaparral H20 Sport with 4.3 Mercruiser MPI ECT with 36 hours
The rear of the boat was partially submerged in fresh water for approximately 12 hours in December 2022. It was immediately taken in for service where the following steps were taken, and parts were replaced:

1. Oil and Filter
2. Starter
3. Alternator
4. Distributor Cap

The boat cranked and ran with muffs. We then took it for a water test where it cranked, ran, but then quickly stalled out. It may be coincidental, but the motor stalled when I attempted to trim the motor down. At this point, the starter would engage, but it would not crank or run.

At this point, I did the following:

1. Installed new batteries (2 x Deka Marine Master 27 series Deep Cycles)
2. Drained the gas tank
3. Replaced the fuel filter
4. Refilled with 20 gallons of non-ethanol fuel

Note, that during this time, the boat would not take fuel well from the gas pump and would overflow easily. There was also water coming out of the vent line during fueling. I found that the carbon filter was saturated with water and was hoping it was the culprit causing fuel starvation. I disconnected it temporarily to test.

While testing, I noticed the battery draining excessively after 1-2 starting attempts, and it appeared that there was not enough power to turn the starter. Now, the starter will not engage at all, even with a full charge on the batteries.

I'm absolutely perplexed at this point and have taken it to another dealer. Any advice or ideas are welcome.

I suspect that you need a new starter which is to be expected after being dunked. You may have corrosion in wiring harness that is shorting and draining the batteries. Would start with a new starter and clean battery connections.

Doesn't sound like you got it running ? Did you get the water completely out of the engine and out of the crank case? if engine has had water in it from December it may be toast.

Also you likely have water in bellows unless drive was pulled (was not mentioned) if water sat in there gimbal and u joints are probably rusted up.

Can you confirm they took spark plugs out and expelled water before trying to start? otherwise may have bent a connecting rod or two...

Salt or fresh?

 

[Alabamangler]

I suspect that you need a new starter which is to be expected after being dunked. You may have corrosion in wiring harness that is shorting and draining the batteries. Would start with a new starter and clean battery connections.

Doesn't sound like you got it running ? Did you get the water completely out of the engine and out of the crank case? if engine has had water in it from December it may be toast.

Also you likely have water in bellows unless drive was pulled (was not mentioned) if water sat in there gimbal and u joints are probably rusted up.

Can you confirm they took spark plugs out and expelled water before trying to start? otherwise may have bent a connecting rod or two...

Salt or fresh?

Thanks for the response. It was submerged in fresh water for about 12 hours and was immediately serviced. The following items were replaced or performed at that time:

1. Water drained
2. Oil and filter replaced
3. Starter replaced
4. Alternator replaced
5. Distributor Cap replaced
6. Gas tank drained
7. Water separator replaced.

The engine cranked and ran after these services were performed, but the problems described have developed. I suspected a fuel delivery issue originally, but after the battery and starter problems, I'm thinking it is a short/voltage issue. I'm not sure of anything at this point.

 

[stresspoint]

check there is no water in the cylinders (hydro locking).

normally a fresh water dunking does very little damage to electrics , 12 hours under water even in fresh with battery's connected could have damaged the wiring harness or some connectors .
break out the multy meter and start checking continuity over the entire harness.
its time consuming but an efficient way to trace your issues.

 

[kenny nunez]

As Scott06 said the wire harness “cooked” internally from being submerged with the battery being connected. You most probably need new battery cables. Also the feed wires to the trim pump could be damaged.
Also the drive needs to come off and the gimbal bearing , universal joints and input yoke need to be inspected.

 

[Scott06]

Thanks for the response. It was submerged in fresh water for about 12 hours and was immediately serviced. The following items were replaced or performed at that time:

1. Water drained
2. Oil and filter replaced
3. Starter replaced
4. Alternator replaced
5. Distributor Cap replaced
6. Gas tank drained
7. Water separator replaced.

The engine cranked and ran after these services were performed, but the problems described have developed. I suspected a fuel delivery issue originally, but after the battery and starter problems, I'm thinking it is a short/voltage issue. I'm not sure of anything at this point.

Ok missed starter replacement.

@alldodge may have some ideas as I don't know MPI's very well

 

[Alabamangler]

As Scott06 said the wire harness “cooked” internally from being submerged with the battery being connected. You most probably need new battery cables. Also the feed wires to the trim pump could be damaged.
Also the drive needs to come off and the gimbal bearing , universal joints and input yoke need to be inspected.

Woud this cooking occur if the engine wasn't running? It slipped off the end of a dock lift when a cable snapped. The trim pump appears to operating normally.

 

[stresspoint]

even without the motor running cables can get cooked.

 

[Fun Times]

Is the engine digital throttle & shift?

There's a possibility there is water inside the PCM if the water got that high.

If used on your engine, the clean power wire harness might be affected too.

 

[alldodge]

Events as I understand after being serviced

Ran for a short time then stalled out
Stalled out when trimming down then would crank but not start (Bad connection)

Then starter would engage but not crank (Not enough power being transferred, bad connection)

At this point, I did the following:

1. Installed new batteries (2 x Deka Marine Master 27 series Deep Cycles)
2. Replaced fuses
3. Drained the gas tank
4. Replaced the fuel filter
5. Refilled with 20 gallons of non-ethanol fuel

Water in fuel rail and pump

There was also water coming out of the vent line during fueling. I found that the carbon filter was saturated with water

Might get some of this water back in in tank

While testing, I noticed the battery draining excessively after 1-2 starting attempts,

There is a short somewhere

 

[alldodge]

If starter engages but doesn't crank and Bat cables get hot, then could also be bearings are seized or its hydrolocked

 

[nola mike]

Gimbal could have seized as well preventing cranking.

 

[tpenfield]

I've learned the hard way that as soon as an engine does not crank, pull the spark plugs check for water and see if it cranks with the plugs out.

Also, you can pull the outdrive for further isolation of the issue.

 

[tpenfield]

BTW - got a serial number for the engine? (I might have missed it)

Is it really the 4.3 and not the 4.5?

 

[Alabamangler]

BTW - got a serial number for the engine? (I might have missed it)

Is it really the 4.3 and not the 4.5?

The dealer showed it to be model number 42410PLUU which is a 4.3L Alpha MPI. How did you learn the hard way about the spark plugs? What were your symptoms?

 

[tpenfield]

The dealer showed it to be model number 42410PLUU which is a 4.3L Alpha MPI. How did you learn the hard way about the spark plugs? What were your symptoms?

Hydro-lock - symptoms were similar to a bad starter. But the engine was actually hydro-locked.