Long story short:

Original block was a 2 piece rear main seal with small donut looking engine coupler. Went to a 1 piece rear main seal block and the triangular style coupler with the new flywheel. This a mercruiser 5.7, I forgot to start off with that. Went to crank the new engine over and it would hit really hard but wouldn't turn. Tried to turn by hand and still no luck. Started looking at the back of the motor and noticed big ass crack right in the top of the bell housing. The motor turned over by hand when we put the flywheel on but didn't check it again after the bell housing was on. What caused this and are there different clearances in the late model housings to accommodate the bigger style coupler. The engine has no water in it FYI.

the triangular style coupler uses a diff bellhousing .you need 1 from a 1 piece rear seal motor .the later small blocks also use a bravo style and that will work for you as well .oso member
jeffs4139 has 1 in the swap shop for sale

Only two days left!!!
http://cgi.ebay.com/ebaymotors/Merc-...item4aab296919

Found one already, I was hoping this was my problem and you guys confirmed it with the help of another good friend, thanks for the quick responses!

Just sucks I have to pull the motor back out lol, live and learn I guess

At least you know what your problem is and you got the parts. Should be an easy fix now. Also ya got a nice piece of cast aluminum scrape to turn in! Just turned in some junk transom plates,bells,gimble housings and rings. 60 cents a pound!

Thats exactly what I was thinking, lol. I also have a junked set of cast iron manifolds to go with it.

you dont have to pull it....just lift it an do it in the sling....