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Jack Plate, Worth it?

Posted: 13 Aug 2019, 17:08
by MrGiggles
Boat is a Tracker 17' Deep V, with an 84 60hp Mercury.

It's currently setup with a hydrofoil and handles pretty decent, however I have had some issues with porpoising. When trimmed up to the "sweet spot" where engine RPMs are highest, it seems like there is fine line between that sweet spot and porpoising, in fact the highest RPM can be attained while it is bobbing up and down slightly.

Without the hydrofoil the holeshot and porpoising is much worse.

I have played with a couple props, I have both a 13P stainless Powertech, and a 14P Turning Point aluminum. The 14P is better for running solo, as I can reach cruising speed with less throttle input, however the 13P has a better holeshot. Neither has much of an effect on the porpoising.

I need to pull the motor and replace the transom sometime soon. I am considering installing a manual jack plate while the motor is off. To any that have put one on, was it worth it?

The cav plate is pretty close to the bottom of the hull right now.

Jack Plate, Worth it?

Posted: 13 Aug 2019, 19:58
by turbotodd
Yes I've run one, 16' Tidecraft (Tide-crap LOL).

It puts more stress on the transom, so you will want it to be fixed properly before putting a jack plate on. It also moves the motor back, in my case 5 1/2", which can change the characteristics of the hull. On mine (different hull than yours obviously), it moved the weight further back, which put the splashwell in the water continually, GF hated it. Additionally the extra weight of the jack plate also makes the boat draft a little deeper at the stern while at very low speeds and at rest. Also it had a tendency to lift the bow quite a bit more while beginning to plane. Top speed increased about 3 mph from 58 to 61, had to change from a 19" prop to a 20" to get the RPM back down. The downside. On a manual JP, you have no way to adjust it while under way, so there's a trial and error period. You will also have to play with propping while "tuning", and for sure you will want a water pressure gauge to watch the water pump pressure. It's not hard to get it mounted high enough to starve the pump which I found out.

I sold the JP to my coworker who needed it, ran the motor on the transom for a while, then put a hydraulic plate on it. The advantage of hydraulic is that you can trim, jack, trim, jack--repeat as necessary, you'll find that sweet spot, the motor runs cleaner, boat picks up speed and the best part is you can change the height for differing water conditions--chop, smooth, shallow, whatever....on the fly rather than a set position. The hydraulic plate and prop changes were worth another 5.5 mph. It liked a prop with a lot of cupping and a little bit less rake. I didn't keep it long after that was all done, guy made me an offer on it that I couldn't refuse and didn't really like the boat anyway for where I was using it.

Jack Plate, Worth it?

Posted: 14 Aug 2019, 09:31
by MrGiggles
Thanks for the input. Sounds like it may not help much in my situation.

I just ordered a Spitfire 4 blade prop. After doing some research it appears that they are good for stern lift and more bite, which should help with my porpoising issue.