Unspported Shaft Length

[Bill Desmarais]

Hell Tony and All,

I’m considering a repower of a fiberglass keel boat.

My calculations show a 28″ to 30″ length of shaft between the hull shaft log forward to the shaft/tranny coupler.

Figure 380 QSB 5.9 Recon power, 8 degree ZF85A gear, 2:1 gear swinging a 22X19 four blade more or less. TBD .

Prop shaft diameter 1.75 inch.

20/40 rule apply here ?

No less than 20 X shaft diameter between bearings? = 35″
No more than 40 X shaft diameter between bearings ? = 70″

Any issue with shaft whip up front with the length ???

Topic

[Tony Athens]

Shaft support

Am missing total shaft length?

Flexible or rigid engine mounts?

Flexible or rigid shaft seal/log?

Tony

[Author]

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