I'm new to the forum and to mud motors. I just bought a 2005 GD 35 SD and put it on a 1642 boat. I ran it for the first time tonite and had a few questions since this is all new to me. The boat gets up good but as is runs the motor seems to want to lift the prop out of the water, is this somewhat normal? when running should the cavitation plate be out of the water? and it seems to be ideling high (haven't hooked the tach to it yet) what RPM should it run at and how do i adjust it, Thanks in advance.

trim tab needs adj and or motor trim up too high go to gd web look at their inst. manual yes cav should be out of water , prop should be about a third out of water at plane

Yes its normal for the prop to want to lift up with speed, there should be about 3-4 inches between the cav. plate and the water. unless you have to hold the prop in the water its fine. tweak the trim tabs so that the motor runs best and the prop stays in the water

Transom height and prop condition.....

GDSD is made for a 16" transom - what is yours ?

Worn prop or poorly designed / reworked prop will have lots of lift...
New GD 3 blade has 3 1/2" wide blades when new - at 3" across the
fattest part of the blade it "pops out" due to wear and excessive lift...
New GD 2 blade has 3 3/4" wide blades when new - at 3 1/4" across
the blade - it is worn out and will do the same thing....

If it is a 2005 - prop would be where I would start - get you a new
GD 3 blade before you do anything else - if you really use the MM you
will likely wear then out every 50 to 100 hours of use in the mud....

Good Luck...

I have the 3 blade prop which appears to be in good shape. Each blade measures 3.5" at it's widest point. Didn't measure the overall width. when I was running it, it was lifting the motor to the point that i was loosing steering and the boat was wanting to veer to one side.

Looks like adjusting the trim tab on the motor fixed the problem. Thanks for the help.