Engine water Lock?

CAn anyone tell me what exactly a Water Lock is on and Inboard engine. I bought a bot and the engine was replaced last year due to a water lock. At least that's what it said on the receipt for the new motor. Also how do you prevent this?

What happens is that water gets into your engine and gets pulled into one or more cylinders. With the pistons are moving up and down, firing and doing their thing, the water will not compress, then when the piston goes up to fire and hits the water and stops, and because of the momentem of the rest of the pistons, crank, etc. it tears everything up in the engine, rods, valves, crank, etc...

The best way to prevent this is to not overheat your engine or submerge your boat.

Its a more common problem in PWC's. I've had it happen to one of mine in the past, once you shoot all the water out of the cylinders spray fogging oil in their and start cranking....I got mine running in a few hours with minimal damage. Technically mine did not "lock", but that's how hydro lock starts.

(Message edited by acurtis_ttu on March 13, 2006)

That's pretty much what I figured, just wanted to be sure, its a brand new 330hp indmar, so I just don't want it to happen to me. I appreciate the input.

Water or "hydro" lock can come from one of several sources.

It is common for a blown head gasket to result in a hydro lock. A small leak between the cylinder and water cooling system will cause the cooling system to pressurize to the max while the engine is running, then when the engine cools down the pressurized cooling system causes water to leak back into the cylinder. When you go to start you have one cylinder with a little bit of water in it. It doesn't take much water to cause the compression to skyrocket and the starter can't turn the engine over.

Another common source of water ingestion on a boat is to back flow from the exhaust. Cooling water is mixed with the exhaust and run out the exhaust pipe. A properly designed system would have the mix point sufficiently low so that water could not possibly flow back into the engine. It is possible, however, that a heavily loaded boat (wakeboard boat heavily loaded???) to the point that the water line is above the "elbow" and thus could allow water to flow back.

Another common exhaust path is if the engine is running poorly and "diesels" when it is shut off. It is common for such an engine to actually run BACKWARDS for second, which means that it starts intaking from the exhaust pipe and can suck water back up.

The third possibility is that the boat was swamped and water was sucked in the intake. As Byrd explained, water getting into a running engine tends to destroy a lot of things.

I would say that if the entire engine was replaced you should be fine, although you may want to take a reality check on how much ballast the boat is carrying

Rod, I appreciate the info, makes me a little nervous, since I have about 1200lbs of ballast in my mobius and we are riding pretty low when we get everyone on the boat, I think I'll go home and let some water out!! Other than that, the engine sounds awesome, my mechanic looked it over and said it runs like a champ, I just wanted to make sure I didn't do whatever the last guy did to lock the motor up. Thanks again.

If you ever do hyrdo-lock, take care of it right away. I had it happen in my Donzi, engine started, stumbled, I gave it gas, and then it backfired and ran backward for a second. Tried to start it - and it make the most god awful noise. I knew what happened - pulled the plugs (water poured out), sprayed some WD40 in the cylinders, and got her running. Then went on a looooong ride (after making sure the oil was not contaminated with water). No probs....