Different Sizes of Flywheel Casing

[eastcoast]

Hi Everyone,

First time posting here. Purchased a boat with an Atomic 4 last year. Ended up having some major issues with the original engine so we bought a donor engine and switched out the core and picked the best of the rest parts. So right now I sit with two complete engines with lots of spare parts.

One thing I've run into that I can't find any information on is different sizes of flywheel casing. When we put the new engine into the boat it didn't fit property - after some checking we realized that the flywheel casing is a bout 1.5 inches deeper than the original. The front cover is also a different material.

My question is - was there a reason for the larger casing? Or was this just a different run? Is there anything I should be aware of or watch out for when switching them out? Is that okay to do?

Any help is appreciated - I tried searching but couldn't find any information on this issue.

[Al Schober]

Early A4s had starters from one manufacturer, later A4s had starters from a different manufacturer - each needs a different ring gear. Later ring gears were bigger and need a slightly bigger flywheel housing. When they made the new flywheel housing, they also made it deeper so they could use a sheet metal cover (save costs).
Early housings, being cast, had tolerances and will sometimes fit the later flywheels - especially if you're willing to do a little grinding. Early housing covers were cast with nice lettering - quite attractive when painted in contrasting colors.
I do not know if the covers are interchangeable. I do know the sheet metal cover will not go on the early housing - it's not deep enough. It may be possible to fit an early cast cover on a deep late model housing, but I haven't tried it.

[eastcoast]

Thanks for the info. Ended up going ahead and pulling both engines apart and ordering the gasket. I was able to replace the thicker sheet metal flywheel assembly with the original cast and lettered housing. Everything works great and it now properly fits in the engine compartment.