Seized engine

[Bill6953]

My Mercruiser 5.0 had trouble starting. Eventually when I turned the key all I heard was "clunk". Mistakenly thought the issue was related to fuel pump or oil pressure/fuel shutoff sensor. So I wasted a couple of weeks replacing those parts with no improvement. When I finally checked the oil I found water in the crankcase and in 2 of the cylinders. Unable to turn the flywheel so I tried adding different types of penetrating oils that I read about online. I broke 2 breaker bars trying to get it to move in either direction. I don't understand how it got this bad in just a fee weeks. There are stories online about guys using this method to free up engines that were out in the elements for decades. Am I missing something?

 

[Bt Doctur]

Remove the outdrive and make,beg,borrow a T bar from pipe and a used input shaft welded up. Remove the heads to determine the damage.
spray a -penetrating oil in the cylinders .
Heat the tops of the pistons with a torch `use penetrating so;vent.
add a length of pipe to the T for leverage and try to get the motor to start turning
a motor has 24 hrs from getting wet in salt water, longer in brackish and fresh
Longer than that and its junk

 

[racerone]

Remove the engine.----Take it apart.-----Inspect repair as needed.----Find / repair the water leak.

 

[alldodge]

^^^Agree

 

[Grub54891]

Where are you from? Up north here we have had freezing temperatures.

 

[Bondo]

My Mercruiser 5.0 had trouble starting. Eventually when I turned the key all I heard was "clunk". Mistakenly thought the issue was related to fuel pump or oil pressure/fuel shutoff sensor. So I wasted a couple of weeks replacing those parts with no improvement. When I finally checked the oil I found water in the crankcase and in 2 of the cylinders. Unable to turn the flywheel so I tried adding different types of penetrating oils that I read about online. I broke 2 breaker bars trying to get it to move in either direction. I don't understand how it got this bad in just a fee weeks. There are stories online about guys using this method to free up engines that were out in the elements for decades. Am I missing something?

Ayuh,...... Welcome Aboard,...... Saltwater, or freshwater,..??

 

[Jeff J]

It could have been hydro-locked which can lead to all kinds of fun things if it was actually ran that way. I had a friend 40 years ago think it would be fun to splash his truck through a puddle. Water made into the intake and trashed the engine. Bent connecting rods and the like. However, just residual water in a cylinder would greatly accelerate the rate of corrosion as compared to an engine just left out in the elements.

 

[Scott Danforth]

Waiting 2 weeks......plan on rebuilding the motor.
Pull the drive, pull the motor, then pull the motor apart

 

[Lou C]

One thing I learned working on marine engines with water cooled exhaust…if all the sudden it seems to not be running right or seems to crank really slow, the FIRST thing g you check is for water in the cyls. I had leaky head gaskets reluctance to start & rough running for the first few min of running. So with the boat on the mooring went thru the ignition (fine) and then pulled the plugs…a lil rust on the side electrode of # 2….cranked the motor and water came out of # 2. Not a lot but some. Soooo with the boat still on the mooring I drained the manifolds & block and sprayed fogging oil in the cyls. Had it towed in. Didn’t know yet if it was head gaskets or manifolds but as it turned out it was head gaskets. Was able to save it even tho it was salt water. Moral of the story time is of the essence check for water FIRST.

 

[ESGWheel]

You did not say when the last time it was running. Regardless, the idea that it was at least 2 weeks with water in the engine / cylinders + unable to turn it over translates to replace or rebuild as folks are highlighting. And even if you could get it turn over and nothing major was broken it more than likely would not run right.

While it is a bummer it can also be a fun project albeit one you did not count on. Make as assessment of the factors of age of boat, emotional attachment to it, your skills and tools you have, ability to enlist family members (great project for those teenagers if you have them!) and of course available budget.

If you do go the rebuild (or even replace) this forum can guide you thru the steps. Give it some thought and please post your decision or further questions. Good luck!