Is there a rule of thumb to determine the right shaft length for a boat? I have a small fiberglass bass boat.

There is no set rule of formula that I am aware of.  It all depends on how your boat sets on the water.  Here is a link that might give you some ideas.

http://www.basspro.com/webapp/wcs/stores/servlet/CFPage?mode=article&objectID=29748&storeId=10151&catalogId=10001&langId=-1

Base to the water plus 10-12 " and longer if rough water.

Remember you can raise motor up, at some point it becomes to long.

Garnet

Shaft length is just the same as it is thrust, get the longest one you can get because sooner or later you 'll need it.

First time I'm voting for a short shaft..........!

When I had 62" it was super on Lake Ontario,Erie, Simcoe when I went shallow all that shaft was in the way.

So the answer is were you fish.

Garnet

i want a longer shaft.  if i am in chopy water i have to put the motor all the way down to prevent it sucking air on the rise.  then i have to bend over to drive.

For what it's worth, Bill Dance says to measure from the water line to the gunnell & add 22".

For what it's worth, Bill Dance says to measure from the water line to the gunnell & add 22".

Hey, you must of watched the same show I did this morning.