How do I change a reverse rotation '79 305 Checkmate engine to a standard rot for a Searay? The Searay has cracked block.

Change the camshaft to standard rotation cam. Replace timing gears with a timing chain set. Reverse the firing order to 18436572. Technically, you should change the crankshaft seals to standard rotation ones, but I've seen it done without changing the seals with no issues.

Distrib gear too??

No. The camshaft and distributor turn the standard direction in both engines.

So a reverse rotation motor uses timing gears instead of a chain?

leave it and make the swich with the drive???

My understanding is the crankshaft has the oiling holes drilled in a different place for reverse rotation engines. I've never had one open to look at so I'm just going on what I've been told. So it may be possible that you will need another crank.

Yes. The camshaft is directly driven with helical cut gears, that's how the camshaft still turns the standard direction. If the camshaft turned backwards, then the ditributor would turn backwards resulting in the oil pump turning backwards... if the oil pump turned backwards, it would blow bubbles in the oil pan rather than pumping oil.

Not true. Somone told you wrong.

Just curious, why was a reverse rotation in a checkmate? I didn't even know checkmates had twin IB boats.
Btw, add a new water pump. Early pumps were directional.

I'm with rd - why do you think it is counter rotation?