350 Mercruiser hydrolock

[lenny2113]

Just purchased a Formula with twin 350's.<br />I was under impression that it was a bad starter on one engine as the engine turned slow and then starter just clicked. <br />It turned out to be hydrolock <br />Pulled plugs, sprayed oil left overnight and turned by hand next day. Turned and started.<br />Checked compression and it's low in 2 cylinders.<br />I will do "wet compression" to eliminate either piston rings or valves.<br />If it turns out to be valves (compression does not rise with oil in cylinder) do I still have to tear the engine down to check the condition of cylinders, pistons, rings, cranckshaft, etc...? <br />I need to determine how water entered the cylinders in the first place. New exhaust, riser installed in spring 2003. <br /><br />Any suggestions please.

 

[loadnet]

Re: 350 Mercruiser hydrolock

No.....<br /><br />If you find that you have low compression in the 2 cylinders in the rear of the engine nearest the transom...<br /><br />Yank the valve cover on the side that you have poor compression after you are done with your wet or dry compression test....<br /><br />You may just have stuck valves on those 2 holes, and they can (in most cases) be freed up by soaking the daylights out of them with PB Blaster and letting the thing sit overnight.<br /><br />Tapping on the top of them with a hammer and piece of wood or brass drift on top the valve stem will help to quicken the freeing up process but just tap lightly.<br /><br />You may have to tap like a hundred million times lightly but they usually will free up and close shut after awhile.<br /><br />Then your compression will be all set.<br /><br />Rust gets into the valve stems and cylinders when water gets shot back up thru the exhaust tubes backing down on the boat..<br /><br />It'll happen if there are no exhaust flappers or broken flappers.<br /><br />Hope this helps you out.

 

[Trent]

Re: 350 Mercruiser hydrolock

Also bad manifolds and risers will cause water intrusion into the cylinders.

 

[akriverrat]

Re: 350 Mercruiser hydrolock

which two cylinders and what were the readings, 1 through 8?

 

[lenny2113]

Re: 350 Mercruiser hydrolock

Trent,<br />I have new risers and new "Orco" manifolds.I'm suspecting blown head gasket.<br />The guy I took it from is a car racer. I think he raced the living hell out of this boat. But the good thing he only used it for 20-25 hours. <br />Is it bad to use platinum auto/performance spark plugs? That's what was he put in the engines.<br />I took a serial number stamped on the block of bad engine it's 14810207. Can you tell the year of engine buy this number? <br />I guess I would have to get manifolds and risers tested for leaks, and if it's good then... It could be exhaust flapper <br /> <br />akriverrat,<br />I will get back with readings and cylinder numbers. I asked marina mechanic to do "wet test" for me. Maybe he would be able to narrow down for sure. <br /><br />Thank you