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Demystifying Jackplates and

How To Choose the Right Dometic Jackplate for Your Boat

The height at which an outboard motor is mounted on the transom of a given boat by the manufacturer or dealer is generally a position selected to provide reliable performance for most situations. It doesn’t necessarily provide the best performance; efficiency and ride are based on a range of situations and conditions that boaters might encounter over a typical day on the water. In other words, an outboard motor that’s in a fixed position on the transom represents somewhat of a compromise — good, but not the best.  

Engine Trim vs. Engine Height

There are two main adjustments boaters can make to engine position while driving their outboard powered boat. One is engine trim, which when adjusted using the trim switch (a toggle usually located on the binnacle control) swings the motor’s propeller over an arc from a position tight against the boat’s transom (commonly called “tucked in”) to an angle closer to the surface and further behind the boat. This is the same control one uses to raise the lower unit completely out of the water, such as when pulling the boat out on a trailer. 
Engine trim can have a significant impact on boat performance and efficiency. For example, an engine that has neutral trim (roughly straight up and down) or negative trim (tucked in slightly) will force the bow down when motor thrust is applied. This can be useful when getting a boat up on a plane from a standing start. Conversely, trying to accelerate from a stop with a motor that’s trimmed out (positive trim) will cause the stern to “squat” and the bow to rise. While positive trim is not good for accelerating from a standing start (hole shot), it does have its applications, such as bringing more of the boat out of the water when running on plane, increasing top speed and fuel efficiency. 

Why a Jackplate?

A jackplate has a different function, and is perhaps even more important in affecting the ride, handling, and overall performance of an outboard powered boat. A jackplate does two critical things: it positions the motor farther back off the transom (known as setback) and allows the boater to precisely control the height of the motor on the transom. Instead of “swinging out” like motor trim, it raises or lowers the entire motor vertically, like an elevator. It does this independent of trim position, and how you position the motor height can have an impact on how your boat runs and performs. 
Jackplates can provide a range of benefits for boaters and fishermen. One of the most recognized is increasing a boat’s ability to travel in shallow waters. By raising the motor height once up on plane, anglers on Texas Gulf “sleds,” flats skiffs, tunnel hulls and other fishing boats can get further back into shallow waters in pursuit of fish.    
In contrast, lowering the motor can help a boat get a good hole shot, and raising it slightly as it gets moving can help get the boat up on plane. Under the control of a skilled boater, jackplates can also improve a boat’s top speed and fuel efficiency. Raising the motor while being underway leaves less of the lower unit in the water, which can greatly reduce drag. This, in turn, can add a few miles per hour to a boat’s top-end speed, while using less gasoline to maintain speed. 
In addition to adjusting engine height, jackplates provide the benefit of moving the motor slightly aft of the transom (set back). This has a couple of effects, the first being increasing the motor’s “leverage” and helping to raise the bow out of the water. This is helpful in getting boats onto plane, especially heavy ones. Another advantage of setback is positioning the propeller out of the turbulent water coming off the hull. Having your propeller in clean, non-aerated water improves performance and efficiency. 

Full Range of SeaStar Jackplates

As experts in fine-tuning boat ride and handling for a variety of vessels, Dometic offers a variety of SeaStar jackplates for different needs and vessel types. With a bit of research, boaters can find an ideal system for their vessel and boating application. 

SeaStar Manual Jackplates

With this basic system, engine height is adjusted manually (over 3 inches of travel) using a stainless steel screw assembly and side locks to securely hold the selected position. This is a good option for boaters looking to find a position that optimizes overall performance and then keeps the motor in that position. While it can be adjusted on the water, this jackplate isn’t really designed for “on the fly” operation.   It's still an effective way for a boater to dial in the ride and performance of their outboard powered boat.

SeaStar manual jackplates are offered in setbacks of 4, 6, 8, and 10 inches and are capable of handling outboard motors up to 200 HP. This makes them appropriate for many boats with popular 4-stroke outboards. 

SeaStar Standard Hydraulic Jackplates

The SeaStar Standard Jackplate is one of the sleekest and most durable engine jackplates available. Available in 4-, 6-, 8-, 10- and 12-inch setbacks, this system uses an integrated hydraulic actuator that lifts engines up to 5.6 inches in 8-1/2 seconds. Its rugged design is ideal for smoothly and precisely adjusting engine height on the fly, even at full throttle. It’s designed for use with gasoline outboard motors up to 300 HP, making it an ideal choice for a range of popular boats like bass boats, bay boats, performance pontoons, deck boats, and others. The SeaStar Standard Jackplate is also compatible with all shallow water anchoring systems.

SeaStar Xtreme Jackplates

With high-strength materials and heavy-duty construction, SeaStar Xtreme Jackplates provide the same smooth performance, fast travel, and durability for boats with gasoline outboards up to 400 HP. Also available in setbacks from 4 to 12 inches and compatible with popular shallow water anchor systems, SeaStar Xtreme jackplates provide high performance boats, premium bass boats, offshore boats, and others with the ability to fine-tune ride and performance. These models are controlled with powerful and smooth hydraulic actuators. For today’s new breed of diesel outboards, Xtreme Jackplates can be used for diesels up to 200HP.  For any diesel outboard models above 200 HP, Dometic recommends using Mega Jackplates.

SeaStar Mega Jackplates

The SeaStar Mega Jackplate line is a meticulously engineered and robustly built electric jackplate system designed for today’s largest, heaviest, and most powerful outboard motors (up to 600 HP). This series is offered in 6-, 8-, and 10-inch setbacks and comes in two versions — a standard bolt pattern designed to fit engines such as Yamaha’s XTO and a wide bolt pattern made to fit Mercury’s 500 and 600 HP outboards. This product has been rigorously engineered and tested to withstand high impact and cyclic loads and comes with corrosion protection anodes. A built-in linear position sensor easily integrates with Dometic Digital Switching for easy control through a central display.

This product brings precision engine height control — and the resulting improvements in ride, performance, and efficiency — to a whole new breed of performance boats powered by today’s super-outboard motors. 
To learn more about jackplates and find the optimal SeaStar jackplate system for your needs, talk with your authorized dealer or visit