Engine swap, OMC to mercruiser

[Scott Danforth]

What keeps the 2 piece RMS from swapping over? Different crank bolt/flywheel pattern?

Stringer coupler buttons only available for 2-piece RMS cranks

Cobra coupler only available for 1-piece RMS crank

 

[nola mike]

Stringer coupler buttons only available for 2-piece RMS cranks

Cobra coupler only available for 1-piece RMS crank

Not to belabor this, but wtf is a stringer coupler button?

 

[Lou C]

The coupler used for the OMC Stringer drives which preceded the Cobras. Up to model year 1985.

 

[Scott Danforth]

Not to belabor this, but wtf is a stringer coupler button?

the stringer drives were the OMC drives available from the 60's to 1985. they used a machined splined "button" about the size of a large hockey puck that bolted to the crank. the intermediate housing was the gear box assembly that bolted directly to the flywheel housing flange on the engine and stuck out the large hole in the transom and had the boot over it.

the cobra drives used a coupler

the larger flanged 2-piece RMS cranks had a completely different bolt pattern than the 1986 and later motors. of the early 1-piece RMS motors, remember, there were minor revisions along the way, however I always suggest getting the 1988-1995 motors unless you want to swap to vortec heads, electric fuel pump, etc.

1986 (first year, flat tappet motor only, some issues with block castings)
1987 (block change, still flat tappet only)
1988-1995 (block casting can support roller cams only some blocks machined for roller cams, some decent heads available)
1996-2000 (first vortec years, roller cams across the board, fuel pump boss no longer machined)
2001-201X (minor changes, primarily adding plastic bits)