How long is a long/short shaft outboard!

[matnoo]

I have a mercuary outboard where the measurement from the 'armpit' of the transom bracket to the lowest point of the shaft is 34" or 864mm.

Is it a long or short shaft?

And just through interest, officially how and where do you measure which part of what to tell?!

Mat

 

[Lakesailor]

I think I'm right in saying you measure from the transom top to the cavitation plate.
Look here http://www.smalloutboards.com/shaft.htm

 

[Kawasaki]

Whether tiss long or short the crux of the matter is where the cavitation plate "sits"
Rule of thumb is. The cavitation plate must align with lowest part of the keel after end.
This applies for your small boat to planing hull types.
Obviously a different story for your auxilliary or main propulsion engine on a vessel sutch as a Yacht drawing 5ft or similar , were the prop needs to be in the water at all times even when your rocking and rolling.
Similarly if an outboard is the auxilliary on a displacement mobo, "prop height" could be called "prop depth" cos the prop needs to be deep enough to stay under whilst bobbing about.
Starting to dribble /forums/images/graemlins/confused.gifnow please have a look at www.onlineoutboards.com before I go really overboard /forums/images/graemlins/grin.gif

 

[oldharry]

Measurement is from the top of the transom to the water line of the engine, usually IIRC the top of the gearbox casing above the cavitation plate. The plate itself has to be well below water line level otherwise the prop will draw air in round it.

'Standard' lengths are 16inches short, and 20 inches for long shaft.

 

[VicS]

[ QUOTE ]
'Standard' lengths are 16inches short, and 20 inches for long shaft

[/ QUOTE ] 15" or 16" "shaft lengths" are sometimes described as short shaft but sometimes as standard shaft. 15" Johnson/Evinrudes are, for example, described as "standard shaft", by the manufacturers if not in the link from Kawasaki's post. The smallest Seagull, the 40 Featherweight, is however accurately descibed as short shaft as it is only about 13". Maybe there are others accurately described as short shaft.

As Kawasaki indicates if a boat is to be subjected to much pitching, a small sailing cruiser for example, it is likely to need a longer shaft model than would be indicated by measurement from the top of the mounting bracket to the water level otherwise the prop is repeatedly lifted out of the water and all forward drive is lost.

 

[charles_reed]

you should measure

to the cavitation plate.

I'd guess yours is a long-shaft