Raising the outboard

[BassinPreacher]

I have done some reading on raising the outboard and still unsure about this.  I have 17' '89 fiberglass Basstracker with a 70 horse johnson.  I checked the bottom of the boat and the centerline of the prop is about 6" below it.  I have read about this needing to be 3".  Is that right and can I do it?  I have two mounting holes I can raise it on the top of the motor mount.(the bottom is just a slide mount)  This could get me another 2" or so.  And what about the blocks below the motor mount, do I need to do anything with those?

Thanks for the help.

[Ben]

You can probably raise it a little, but before doing it,  I highly recommend you have a water pressure guage before going up very much.   Those you are reading about running 3" below the pad, you're missing a couple of key points.  I think you will find just about all of those motors are on 6" or more jack plates, and most of those boats have a built in set back to boot, so the leading edge of their LU is sitting back 2 ft or more from the pad.  The prop shaft is actually running deeper than 3".  With the motor straight to the transome, I would think 4 - 4 1/2" below the pad is about the max you raise it, but like I said, messing with engine height without a water pressure guage is risky business.  Could find that to be a very expensive 1 - 2 mph.  

[Bass_junky]

All documentation I read when installing a jack plate on my boat referenced 3" centerline to bottome of boat for a starting point.  This is a reference only.  Issues with water pressure should play a key role in this adjustment.  The higher you raise your motor The better top end speed but hole shot is compromised.  The lower the unit the better hole shot but less efficient at top end.

All of this is also dependent on boat load.  So these adjustments should be made on an avg load for your boat.