1987 Mercruiser 305 with cracked block

[boaterinsd]

My plan was to get it started to see if it ran , which it did. Good sized outward crack starboard side, small crack port side. Was just gonna pull it and swap in a 78 350 I found with good compression. Till I discovered the crack bolt pattern on mine is smaller (one piece rms) and my planned replacement is bigger( 2 piece). So the flywheel that the coupler mounts to is or isn't the same for the older motor?
I am not gonna buy older motor is I can't simply make it work, right. Or do I ?

 

[boaterinsd]

Are couples different between the 2 motors also? Someone told me to put a manual flywheel on the older block and I could mount my current triangle coupler? Or not

 

[Scott Danforth]

You need a 1986 or newer motor. The 1978 is 2 generations older

You want to stick within your generation or newer

I would suggest a 1996 or newer vs stepping backwards

FYI, the SBC major design change years are as follows

1968-1978
1979-1985
1986-1988
1989-1995
1996-2000
2001+