Shaft spin on Atomic 4

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RubyJean

RubyJean

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Jan 1, 2013
54
Oday 27 Coos Bay, Oregon
Hi all, I recently bought a O Day 27 in great shape. My question is that I'm changing the folding prop to a fixed blade. Do I need to install a shaft brake to stop the shaft from spinning? The boat has a new rebuild on the Atomic 4, but not sure about the tranny type. I know some type's can be damaged by letting the shaft spin.. Michael..
 
CalebD

CalebD

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Jun 27, 2006
1,479
Tartan 27' 1967 Nyack, NY
If it is a 'direct drive' A4 then it is a 1:1 transmission and the prop needs to be a right handed (RH) prop.
I don't think you need to install a shaft brake as locking the shaft in forward (FWD) should stop any free wheeling of the prop while sailing with the engine off. Left in neutral the shaft can spin, but not in forward.

Disclaimer: I've owned a boat with a direct drive transmission A4 for 10 years.
 
RubyJean

RubyJean

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Jan 1, 2013
54
Oday 27 Coos Bay, Oregon
Thank you, I just don't have any info on this yet. I was hoping this was the case.. Michael..
 
Herrick18911

Herrick18911

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Apr 11, 2005
57
Bayfield 36 Rock Creek
Completely agree with that second post but we always put the transmission into reverse to stop the prop from free wheeling. That's what we've always heard from others as well.
 
CalebD

CalebD

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Jun 27, 2006
1,479
Tartan 27' 1967 Nyack, NY
Herrick,
It really depends on the transmission. I know many diesel powered boats will use reverse to lock the shaft.

In this case, the OP is talking about an Atomic 4 gas powered engine where the tranny IS the back end of the engine. Because of the way the clutch(es) engage on this type of tranny only forward will reliably and safely "lock" the shaft. There is no 'detente' in reverse, only in forward, meaning only forward can be locked in place.
 
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