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How do I un-seize my engine?

2008 November 28
Dear Boat Doctor,
I sail a Nor'sea 27 on Lake Michigan, the boat has a Yanmar 2GM20 engine. I have not been sailing a lot over the last few years, and thus not burning a lot of fuel. As a result my fuel is a little funky and I have been clogging fuel filters.

I was out the other day in fairly rough water, a filter clogged and the engine stopped. I changed my filters and bled the engine but couldn't get it to start. My friend told me the engine is seized. What do you think?

James Blake
Darien, Illinois

Dear James,
Without looking at your engine I can't give you a definitive answer, but I can give you a list of things to check. Assuming that your friend is correct, there are only a few things that would stop an engine from turning.

If you cranked the engine for a long time you may have hydro-locked it. This occurs when the water pump fills the exhaust with water and it runs back into a cylinder. Liquid is not compressible, so when the piston tries to come up it will seize the engine. You'll need to remove the injectors to get the water out of the cylinder, and then change the oil many times to get the water completely out of the engine. The proper way to avoid this is to close the engine seacock until the engine starts.
You may have clogged the injection system with dirty fuel causing it to spray too much fuel into a cylinder, this is also a form of hydro-lock. Again you'll need to remove the injectors to get the fuel out, change the oil to remove the excess fuel and then have the injection system serviced.

There is also a remote possibility that you have a stuck valve. The easiest way to check for this is to open the valve cover and check to see if the valves operate. If a valve appears to be stuck, you may be able to break it loose by gently tapping it.