In my manual for a new small Yamaha 4hp tiller it said that the cavitation
plate (oval disc above your propeller) can be anywhere from even with the
bottom of your boat to 2" below the bottom.

I wanted to run shallow in our local rivers so I shimmed it with some wood
on top of the transom and made it even with the bottom of my boat.

If you get it too high your motor with cavitate (suck air).

If it is too deep the surface of your motor under water can actually slow
your boat some and may be more prone to hit submerged things.

I think if yours is somewhere from even with the bottom to 2" below the
bottom you will be fine.

With very large outboards many now use automatic (hydraulic/electric)
vertical engine lifts (jack lift or jack plate) to adjust the depth of their
outboard.

With this and power trip & tilt plus trim tabs you can really adjust the
ride, performance and fuel economy of a mid-size (100hp+) outboard powered
boats.

--
Bill Kiene

Kiene's Fly Shop
Sacramento, CA, USA

Web site: www.kiene.com


"kdschreck" wrote in message
oups.com...

I just read an old message (2003) in which it was suggested that there
is a tolerance of about 3" for adjusting the length of an outboard. I
didn't see this in the manual for my engine. Can anyone explain the
process? (I have a Mercury 9.9 long shaft, tiller model.) Thanks,
kdschreck