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-   -   Reverse rotation change (https://www.offshoreonly.com/forums/do-yourself-boating-budget/228572-reverse-rotation-change.html)

GaryG 04-17-2010 07:47 PM

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

cubicinches 04-17-2010 07:53 PM

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.

US1 Fountain 04-17-2010 09:06 PM

Distrib gear too??

cubicinches 04-17-2010 10:49 PM


Originally Posted by US1 Fountain (Post 3089816)
Distrib gear too??

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

US1 Fountain 04-17-2010 11:14 PM

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

phragle 04-17-2010 11:17 PM

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

Reed Jensen 04-18-2010 04:59 AM

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.

cubicinches 04-18-2010 07:27 AM


Originally Posted by US1 Fountain (Post 3089868)
So a reverse rotation motor uses timing gears instead of a chain?

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. :eek:


Originally Posted by Reed Jensen (Post 3089899)
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.

Not true. Somone told you wrong.

rdoactive 04-18-2010 09:03 AM

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.

Mbam 04-18-2010 12:40 PM

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


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