Jack Plate Installation

I am thinking of installing a manual jack plate to maximize my setup. What are the typical adjustments I will need to make? It seems that with the motor farther back, I would need to make some steering adjustments? Is there anything else I should factor into the investment, and how difficult is it to make the adjustments?

Re: Jack Plate Installation

are all your control cables, and harnesses long enough.

Re: Jack Plate Installation

Aqua, If the control cables, steering cable and wiring harness and fuel line are long enough, that is all there is to it. You will probably want to pack the tools necessary to do the jackplate height adjustment, and take a nice ride. It wil take some fiddling to get the height correct. Also, if you have the "fin" type zinc anode on the motor, you will find that it looses it's effectiveness as you raise up the motor. At speed the motor will pull to the right.

Watch the water cooling intake, as you raise the motor. You do not want to fry the motor. I plugged thetop hole on my motor, and filed the bottom hole larger to compensate.

Re: Jack Plate Installation

You will want a water pressure meter. Water pickup may be an issue.
I've heard that you raise the cav plate on the motor 1" for every foot you set the motor back.
Bobs Machine Shop is a helpful sourse.d

Re: Jack Plate Installation

The ammount you can go up depends on how much V the hull has and what the transom angle is. A (very) general rule of thumb is for every 5-6" back you can go up 1". That will put you back to "square 1". Then you can adjust up from there.

The Bob's manual 4-in-1 is a great piece.

Re: Jack Plate Installation

Thanks for the replies. I do have a pressure gauge already, and I will monitor it closely. My biggest concern is the additional $ investments after buying the jack plate. If I have to start replacing wiring and steering cables, it won't go over well with the wife. It took a while to get her to agree to spending money on a jack plate.

I do have one more hole left to go before I max out the engine height without a jack plate. Right now I get about 5,280 rpm, so I figure I need to gain an extra 520 rpm. Is it reasonable that lifting the motor to the last hole can get me the extra rpm I need, or should I go straight to the jack plate?

Here is some more information about my boat:

* 1978 Glastron SSV-188
* 1978 Johnson 140 hp
* Top GPS speed 37 mph
* WOT is 5,280 verified by 3 separate tach's
* Prop is a 15 pitch Rapture

Re: Jack Plate Installation

I would try the last hole, and see how it goes. How high above the boat bottom is the A-V plate, at this moment?

Re: Jack Plate Installation

I am about 1.5 inches from the bottom of the boat, but I still have a steady 25 psi on the pressure gauge.

Re: Jack Plate Installation

In that case, raise it up and see if it ventilates.