Jack Plates 101

[MarkR]

I am seeing a lot of boats with “jack plates� or “set back plates� I’m not exactly sure what you call it. The guys say they get a lot better fuel economy and more speed from using it?

Is this true? How does it work? I’m thinking that if the propulsion is further behind the transom the boat might be riding higher when on the plane. Does this make sense? And then also why is the position of the prop raised when a jack plate is used?

[catfishtonyd]

Technically a jack plate is a vertically adjustable engine mounting bracket. Â*

A set back plate does just what the name implies. Â*It set's the engine back from the transom.

Now. Â*For all practical purposes, they're one and the same thing, since both features are incorporated into the same unit.

What they do is set the engine back further from the boat, allowing more leverage for the engine to lift the boat. Â*Remember, the longer the lever, the less force it takes to lift a load. Â*(within reason) Â*Generally plates vary in set back from 6-12 inches. Â*How much you need or want depends on your boat, engine, load etc. Â*The set back also allows the engine to get a better bite on clear water behind the boat.

The jack plate part of it, allows you to raise the engine for less drag. Â*You have to be careful of course to not raise it too much or you can lose water pressue to the engine, and overheat it.

As a loose rule of thumb, you raise the engine until you hit a point where you are hitting maximum rpm at WOT and holding good water pressure. Â*Decreased drag from the lower unit, and more lift for the hull translate to more speed, and better fuel economy. Â*(In theory)

The ultimate is an electric/hydralic jackpate that is adjustable from the drivers seat. Â*

[MarkR]

Thanks !!
But I have some blunt questions on what you said.

What is WOT?
How do you know how much to set the motor back?
If I was to install a jack plate or set back plate on my boat will it be necessary to extend the steering and control cables?

Will you actually get better fuel economy or is this only a sales trick?

[Rob Mak]

lou
they call it wetted surface or in plain terms the less of the boat in the water the faster you will go pre throttle setting. for example if you are running 50 mph wide *** open then install a jack plate say an 8"er at wide *** open you may well be running 65mph. fuel econamy is stated pretty much like this. ya get a fast plane time-hole shot-ya can run with less throttle at the same speed. which in turn burns less gas.

this is it in a nut shell
hell i still can't figure out what WOT is


zooker

[fredhatch]

WOT- wide open throttle.

[MarkR]

oooohhhhh! I like WOT ;D

[catfishtonyd]

I don't think there is any set formular for how much set back you need. Â*It's more a factor of the hull design than anything else. Â*I've never had one with more than a 6" setback, but have seen them with as much as 12". Â*Generally speaking, the faster a hull design, the more setback you can use. Â*Keep in mind that some hulls are not designed for any setback, and it can void your warranty. Â*I've never talked to a manufacturer Â*that would recomend any setback. Â*They'll all tell you that you don't need it. Â*Well that's right. Â*You don't NEED it. Â*That's not to say it won't help.

What type hull are you running and what size engine?

You probably will need to replace the steering and throttle/shift cables unless the ones you have are too long already. The further back you set the engine, the more likely it is that that will be true.