Boating Accessories

A Jack Plate Expands a Boat’s Utility

jack plate, SeaStar jack plate, hydraulic jack plate

SeaStar makes a variety of hydraulic and manual jack plates.

For outboard-powered boats including rigid-hulled inflatables (RIBs), there is no ideal engine height suitable for any combination of hull, prop and load. Each setup can have its own specific ideal engine height.

So, the question is can we create the ideal mounting height for our engine in any combination of the above factors. The answer is yes if we use a hydraulic jack plate. By using a hydraulic jack plate we can achieve the perfect setup every time and get as close as possible to maximum boat performance in each condition.

A jack plate is also a bracket that positions the engine anywhere from 4” to 12” (10.16 cm to 30.48 cm) farther aft. The advantage of moving the engine farther aft include the following:

jack plate, SeaStar jack plate, hydraulic jack plate

A hydraulic jack plate lets an owner change engine height with the push of a button.

Mount the Engine Higher

The further we set the engine from the transom the higher we can raise it. We can raise the engine by a height equal to the amount of setback, maintaining a relationship of approximately 4:1, depending on the propeller For every 4” of setback, we can raise the engine about one hole higher.

Improve the Propeller’s Efficiency

The farther we move the propeller form the transom, the “cleaner” the water it operates in is. This improves its bite, optimizing its efficiency. The depth of the water a propeller should run in to reach its optimum efficiency depends on its specific characteristics.

Each propeller (based on its diameter, pitch, number of blades and other features) is designed to perform better a specific engine mounting heights. Some props are designed to perform better when fully submerged in the water, while others are mad to run near the water surface. Even with two propellers designed to run high in the water, one will out-perform the other when it is running higher.

Maximize Boat Performance in Relatively Calm Water

When weather conditions permit or when the boat is lightly loaded, we can raise our engine higher. This leads to less gearcase in the water, decreased lower-unit drag and increased top speed.

manual jack plate, Bob's Machine Shop, Bob's jack plate

A manual jack plate is an affordable way for an owner to adjust engine height.

Maximize the Boat’s Performance in Rough Water

When we travel in rough water, we can lower our engine more than normally to have our propeller deep in the water. This means that we get maximum thrust because the propeller gets its best bite. We can stay on plane at lower possible speed while we will climb the big waves.

By lowering our engine we ensure high angles of positive trim that let us hold the bow higher when the conditions require like when we are running in following seas.

Control the Ride Attitude

Many times, the boat’s center of gravity shifts farther back or forward according to our load position. In this case, with the help of the jack plate we can “correct” the negative effects of the center of gravity’s shift in our ride.

bass boat, Ranger bass boat

Many bass boats have jack plates that improve their performance and let them get into shallower waters.

Navigate in Shallow Waters and Protect the Engine

A jackplate lets us ride into shallower waters and lift the engine fully out of the water when docked at a marina. This helps protecting many against corrosion.

Better Fuel Efficiency and Lighter Handling

When conditions permit, we can lift up our engine and travel with less drag on the lower unit and the propeller blades that are running in cleaner water, which leads to lower fuel consumption.