BoatBanter.com - View Single Post - How Long the Shaft of an Auxiliary Motor Should I Get?

On 31 May 2006 11:09:17 -0700, wrote:

I am planning to get a 9.9hp outboard motor as an auxiliary motor. But
I don't know how long the shaft should I get.

As I understand it, the cavitation plate (horizontal surface above the
propellor) should be at least several inches below the bottom of the
boat when the motor is fully lowered. This is to prevent turbulent
water and air from being sucked into the prop, which causes over
reving and excessive slip (cavitation). Obviously your choice of
mounting location for the motor bracket plays into this decision.