Hi
I have a MERCURYSERIAL #1B541204 (10/03/2007 250 PROXS DFI L 3.0L). The motor sat for the winter in a garage. I went to start it today and it wouldn't turn over. Putting a socket on the fly wheel I can turn it only 3/4s of a revolution one way then it stops dead. I then can turn it in the opposite direction 3/4s of a revolution and then it stops dead. This is with the spark plugs out. Just to eliminate causes I dropped the lower end and took off the accessory belt. I can see each piston go up and down. I added oil to the cylinders and turned it over a bit before reinstalling the plugs and putting it away for the winter. I have never had this issue. I cant see anything strange on the plugs or tops of the pistons. I am supposed to Cobbie in Maine tomorrow. Any ideas would be greatly appreciated.

Thanks
Ralph