Volvo Penta Water in pistons
 

I have a 2017 Cobalt with 300HP Volvo Penta motor with 70 hours that has water in the pistons. I have been without the boat for 6 weeks while Volvo and the marina try to figure out how water got into the pistons. There are 2 other boats at the marina with the same issue. One is 2016 and other is 2019. I'm told there are many others throughout the country with the same issue. Volvo has no answer as to how the water is getting into the pistons and has decided to replace a bunch of parts in hopes of solving the issue. I was wondering if anyone has had or is having the same problem.

Had that happen once when I was running at 30mph and the kill switch was enacted causing the boat to come to rapid halt and large backswell against the transom. Boat would not start. Called buddy and he said water lock. Pull all plugs and crank her until the water blows out. Been running fine since. Maybe not your issue but figured I’d mention.

Is what in the actual engine cylinders? Or has water infiltrated the trim pistons?

I believe the water is actually in the engine cylinders. They replaced many parts including the manifold, catalytic converter, all the gaskets etc. They also replaced the flywheel and starter both apparently damaged while they were trying to start it prior to finding the water in the cylinders.

I had the same thing happen with a Volvo engine in about 1990.

My boat was in a boathouse in an area that continually gets waves. Somehow the waves against the stern allowed water to go in through the drive, through the exhaust headers, and get into the engine. When I attempted to start the boat, the bolts on the starter broke from the torque because the motor wouldn't turn. Water doesn't compress easily.

They had to replace the starter but eventually put different exhaust headers in with a hump in them. That prevented the water from entering the engine.

In my experience as an automotive mechanic of 30 years I had a volvo engine do the same thing and after days of trying to figure it out I found that the aluminum block had a casting issue and was seeping through the block and I have seen it in the aluminum heads as well. I would think that if the engine is hydro locking the water is coming in to the cylinders through one of the cooling jackets in the heads . Not saying that's the problem but a good place to check.

If this the motor.... I would be looking at the design of those catalyzed exhaust manifolds! Any leak at all and the motor will ingest water and possibly hydrolock!

Woodsy

Woodsy, I'm not sure if those are the same manifolds, that looks to have a coolant reservoir on it which would suggest a closed cooling system. I am guessing the OP's motor is raw water cooled. I'm not sure what those manifolds look like, but I would think it is a different design. The only way water can get into those cylinders would be through a leaking head gasket or leaking riser manifold gasket, or a wave hit the back of the boat with enough force to flow up the exhaust system and into the cylinder. I'm not sure how else it could get in.

Is it a closed cooling system or raw water? If it is a closed system it would have coolant in it in that tank on the front of the motor in Woodsy's picture. I believe those are set up to pass the coolant through a heat exchanger that is cooled with raw water. The marina should be able to run a pressure test on the cooling system to determine where the leak is though.

Thank you all for your comments and suggestions. It is an uneasy feeling not knowing the cause I would be more comfortable if the cause had been identified and fixed. I am worried this could happen once again next season when the engine is out of warranty and once again lose 1/3 of the season.

exhaust
 

If they have not identified it, it was probably through the exhaust. My Bravo 3 (essentially a copy of VP) Mercruiser 6.2 MPI ingested through a bad flapper coming off plane into the hole in the wall a few years back. Fun place to wait for a tow!

Regardless of warranty, your issue is documented. I would take it easy coming off plane. I have notice a lot of people pulling tubes/ skiers will pull off throttle a little too fast and their wake will catch them.

Best of luck!

GTO....
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Even if it is a closed cooling system... they need to pump raw water thru the heat exchanger and that hot water gets dumped out the exhaust.

Woodsy

Bad riser gasket then maybe, or just bad design allowing reversion up through the manifold when slowing down?

I've never had a closed cooling marine engine apart so wasn't sure what they did with the heat exchanger water.

VP used to use exhaust flappers/water shutters in the exhaust system just downstream of where the cooling water mixes in with the exhaust gases. For some reason they stopped about 20 years ago. They were there to prevent water from coming up into the exhaust when the boat decelerates rapidly.

I would guess that your engine is a bit too low relative to the water line of the boat and water can make its way up too easily. Risers between the manifolds and elbows were a common fix for this, but some new exhaust designs don't allow for this because the manifolds and risers are one piece. I'm not sure what can be done for your boat, but you should never ever pull the throttle lever to idle while on plane, always slow down gradually unless there's an emergency.

Your starter (likely a Delco PG260M) has a planetary reduction gear set with a plastic ring gear that will fail if the engine is hydro-locked. You can usually just replace the $10 gear https://www.walmart.com/ip/New-Gear-...E&gclsrc=aw.ds to fix the starter.

Figure it out?
 

Maddie. Did you figure out where the water was coming from?

No. Volvo had no idea and neither did the marina service. They replaced a bunch of parts after being pulling the engine and the boat being out of service for 6 weeks in the middle of the Summer. When I finally got the boat back I put about 10 hours on the motor without any issues.