The hydraulic jack plate is one of the most mis-understood items aboard many bay and flats boats. Many people see them and think about draft, draft, and draft, but truth be told, there’s a lot more to this story.
While the concept is simple – raise the outboard without tilting it – many people think a jack plate will allow them to get into 6″ of water with a boat that has 9″ of draft. And truth be told, this is initially true; a jack plate can be used to reduce draft by an inch or two while running, since it allows you to raise the drive slightly higher than you’d be able to tilt it without blowing out the prop. There’s just one problem: as soon as you stop in that shallow water, you’ll be stuck there. Your boat’s static draft is usually several inches more than its running draft, and even if the keel is still off the bottom, you won’t be able to pop onto plane with the drive unit raised up as high as the bottom of your boat (in most cases – tunnel hulls can be an exception).
Okay, so the draft you save comes only while on plane – this is still a good perk, since you can run over shallow flats to get to deeper waters, where you’ll find fish and then later be able to hop back onto plane and skim the surface to freedom. But for most of us, the cost of a jack plate may well out-weigh this lone benefit. Wait a sec – this is only a small part of the story. By being able to adjust drive height without tilting the engine, you can see a significant speed and efficiency boost. You also get a performance boost since the jack plate moves the engine several inches aft of the transom, which often improves the boat’s balance and natural trim angle. In fact, jack plates were used by racers and speed demons long before anyone tried using them to reduce draft.
Just how much speed and efficiency will you gain by adding a jack plate? That depends on the type of boat you run, its hull design, running draft, and a host of other factors. But the bottom line is this: the advanatges you’ll gain with a jack plate go far beyond mere running draft and on most bay and flats boats, once you’ve tried using one, you’ll never again want to run without a jack on the back.
Do you need a jack plate?
Installed fixed jack plate, 6″ back and 6″ up w/ anti-cavatation plate. This is on a 16′ flatbottom w/ 60 hp Yamaha 4 stk. The object was to run in shallow water, the increased performance suprised me. And one new thing learned is when running at desired throttle setting adjust trim by watching tach. At rpm peak boat is running with least resistance hull angle to water.