[Pub911]

A new 'feature' of the ZF-6 transmission, as a replacement for the Hurth HSB 50, is that it's 1" longer. This means that the prop shaft is 1" longer at the business end. On my setup, this means I go from about 4" to 5" of exposed shaft between the end of the cutlass bearing and the prop, itself.

I know alignment is required regardless, but should I go through the hassel of have the shaft shorted, rekeyed, etc?

Clearance is not an issue.

 

[scottyt]

i cant see that as a real problem, but why did you not have it shortened ?

 

[Pub911]

Cost and wasn't sure if I needed to shorten it.

 

[Maine Sail]

The recommended

The recommended hang over distance between the cutlass bearing and the front edge of the prop hub is 1X the shaft diameter max. Beyond that and you can start to create shaft whip. 4" inches is way too much but 5" is really bad..

Per ABYC Standard P-06

6.5.5.4 The distance between the forward end of the
propeller hub and the aft end of the last strut bearing shall
be limited to one shaft diameter.

 

[Pub911]

my shaft is 1"...I don't think I could fit a zinc on the shaft if all I had to work with was 1".

Still, appreciate the reference and advice.

 

[Fstbttms]

my shaft is 1"...I don't think I could fit a zinc on the shaft if all I had to work with was 1".

What kind of boat are we talkin' about?

 

[Pub911]

1972 NorthStar (aka Hughes) 38.

Fin keel skeg-hung rudder. 25hp diesel.

 

[Fstbttms]

So the shaft exits the hull at the keel and is not supported by a strut?

 

[Pub911]

correct. no strut. the length of the shaft overall is about 6' - in case that matters.

 

[anthon]

I wouldn't be comfortable with 5" of exposed shaft.
I'd get it shortened to 3" max.

 

[Valiente]

With no cutlass bearing, that's too much exposed shaft in my opinion. More isn't better in this case. I would ask on the Hughes 38 owner's page, if such a thing exists. Mine shaft comes out of what used to be called the "deadwood" at the end of a full keel, but you can see how little space there is: