Q; Raise the Jack Plate or Lower the Jack plate?

Big Ed · Post by **Big Ed** » Sat Apr 19, 2008 3:04 pm

I have been playing a little bit with my manual Jack plate.

When i first got the boat it was flush on top. It ran great and still does. It seemed as though i was more out of the water at that time. I dropped the jack plate 1/4" lower than flush. Now it feels like i am not out of the water as much as i should be at full plane.

I am around 5100-5200 rpm at wide open throttle and running around 63mph with a 25P prop. I have a Champion 200DCX Elite! It is equipped with a 225HP Murcury ProXS.

How can i get my boat more out of the water? Do i lower or raise the motor on the Jack plate? Will that improve overall speed and RPM or will it decrease it? Will i also get better or worse hole shot?

Thanks for your help; Big Ed!

mark poulson · Post by **mark poulson** » Sat Apr 19, 2008 3:26 pm

Ed,
Jordan at Anglers told me that the higher the motor, the better your top end.
The lower the motor, the better your hole shot and handling.
He said every boat was different, and you had to be careful and watch your water pressure when you're raising the motor, because you could raise it too high and get into the cavitation caused by the hull at high speed, so your motor doesn't get enough cooling water.
If I were you, I'd call Jordan.

Big Ed · Post by **Big Ed** » Sat Apr 19, 2008 7:59 pm

Thanks Mark;

So does raising the motor raise your boat up out of the water while on plane or will it lower your boat while on plane?

I usually run between 15 - 17 psi of pressure. Does that sound about right?

Thanks for your help; Big Ed!

smpboy · Post by **smpboy** » Sat Apr 19, 2008 9:46 pm

only 63 that thing should do 70s with a 225 xs on it something is out of wack wish i could help but iam still learning myself

mark poulson · Post by **mark poulson** » Sun Apr 20, 2008 1:36 am

Ed,
I really don't know any more than I posted before. Jordan explained the concept, but I don't know any more than that. You really should call Jordan at Anglers.
In the mean time, if I were you, I'd move the jack plate back to where it worked best for you.

FRANKRIZZO · Post by **FRANKRIZZO** » Sun Apr 20, 2008 1:49 pm

raise it 1" my scx200 with a 225 proxs hydraulic plate runs 72 @5800 24p tempest in the summer at elsinore

fishinman · Post by **fishinman** » Mon Apr 21, 2008 1:48 pm

For more speed run a 3 blade prop. Less speed by as much as 5 mph but more control and better hole shot run a 4 blade prop. The whole idea behind motor position is to place the motor with or without a jack plate high enough on the transom so that at full trim full throttle on glassy condition your prop has the full bite of the water with the least amount of boat in the water with a little chin walk so trim just a tad down and your cookin, bookin as fast mr. Merc , Yami, or Ms. Suzi will take ya. Expermintation is the key!! The prop type and design can get kinda complicated but a professional prop shop could help ya in that area if you so desire for extreme efficentsy

Oldschool · Post by **Oldschool** » Mon Apr 21, 2008 2:07 pm

ED, the jack plate moves the engine back away from the transom and that changes the planning pivot point to increase the length of the hull and gives the prop more leverage to lift the bow. The starting point for the distance from the planning surface to the prop hub center line is around 3 1/2 inches, with the engine cavitation plate level with the planning surface. Trimmed down all the way will push the bow down and trimmed up will lift the bow up. The limitation to how high you can raise the engine above the planning surface is the water pick up holes; too high and you start to suck in air and loose water pressure.
Prop cup and rake also affect bow lift and the more blades in the water increases drag, reducing RPM's, like a car in low gear.
Your set up sounds like your prop center line is too low. Measure it first, then bring it up to 3 1/2 inches to start with, then increase it by a 1/4 at a time and check the performance.
Tom