Personal opinion: What caused a dead cylinder

Yamaha V6 2-stroke injected CDI with about 1K hours.

Last year the boat flipped and sat for 24 hours in water. Taken out and "serviced" by a Yamaha mechanic. The boat ran perfect all year but at the end of the year developed a hard knock that you couldn't even run the motor with.

I did a compression test, came up with 40PSI on one of the cylinders (the bottom one on the port side). Pulled the head to find a great deal of inward and outward movement (not side to side). Also pitted head and metal stuck in one of the side ports. I'm suspected that the big end of the rod bearing has failed causing the movement.

There is good compression on all the other cylinders with no scoring of any kind to intake oil starvation.

What is your personal opinion of this issue? cause and effect?

Thanks!!!

Re: Personal opinion: What caused a dead cylinder

Caused by water damage incurred during submersion. One or more needles in big end of the rod eventually disintegrated.

Had exactly the same thing happen to a Yammy 130 V4. After servicing ran fine for about a year, then threw a rod.

Re: Personal opinion: What caused a dead cylinder

That's what my thoughts were as well.

Cost $6K and now the motors gone, not a good start to the season.

Re: Personal opinion: What caused a dead cylinder

Should have taken the insurance money and bought a different boat and motor to start out with.
I have never heard of one going under and not ending up with problems in the long run.
Kind of like I would never buy a car that was in a flood

Re: Personal opinion: What caused a dead cylinder

My personal opinion on this, is the motor should have received a new/reman powerhead instead of the service that was performed. All of the electronics were replaced on the motor and carbs rebuilt. realistically, the electronics would have been fine with a fresh water flush and cleaning all connections. Since the stator windings are seals, along with the CDI and voltage R/R (all sealed units). With a new/reman powerhead the electrical issues that arose would have been simpler to repair then having to deal with this issue now.

As for the flooded vehicles, that's a little different as water in an automotive engine get's flushed out with the oil pressure. With a 2-stoke motor you don't see oil pressure at the main and rod bearings thus not being able to remove salt or sediment from the bearings unless a full crank rebuild took place.

Feel free to correct me if I'm wrong in any of my above statements.

Re: Personal opinion: What caused a dead cylinder

Update: Looking for a new/used motor OR a powerhead...

What is the average time to swap a power head on this motor? it's a 1999 175HP V6..

Also is it worth messing with a powerhead? or just get a used motor...