BAY BOAT ANGLERS, bass boaters, flats boat fishermen, and others who like to run through skinny water often get a jackplate for their boat.
Sure, they can be expensive, but they let you get into shallower water, right? Well, yes they do. They help you get back out of it, too, allowing you to jump on plane without squatting at the stern.
However, this isn’t even the greatest advantage a jackplate provides. Truth be told, boaters of all sorts would benefit from having a jackplate between the transom and the outboard.
Jackplates can net a slight efficiency boost for just about any outboard-powered boat on the water. To understand why, you need to get a clear picture of what a jackplate allows you to do: raise and lower the outdrive, without changing tilt.
Normally, when you trim your outboard up, it not only raises the outdrive in the water column but also changes the angle of the propeller’s thrust. The higher you trim, the more it pushes the transom down and the bow up.
Savvy boaters will already know that the most efficient cruise is usually attained by trimming your outboard up as far as possible before it starts ventilating. That’s because trimming up minimizes the amount of lower unit that’s in the water, creating drag.
But not all boats will be at their most efficient running angle when the engine is trimmed all the way up—in fact, very few will. Trimming the drive up with a jackplate, on the other hand, allows you to minimize the amount of lower unit in the water.
It also maintains whatever trim angle is best for your boat, channeling the thrust in the most efficient direction. The engine can be perfectly even, tucked in slightly, or trimmed out slightly, and you can control how deep the lower unit sits irrespective of trim angle.
A jackplate also provides setback, moving the engine farther aft behind the boat. As you get aft of the transom of a moving boat the water rises back up, so pushing the propeller aft means a higher running waterline for the lower unit. Each inch of set-back provided by a jackplate allows you to raise the engine by about another half-inch, in many cases again providing an efficiency boost.
A jackplate moves the point of thrust aft of the transom. This moves the pivot-point farther aft as well, enhancing tight turning abilities. It also exaggerates the effects of tilt and trim, since it increases the fulcrum between the propulsive force and the boat’s hull. This has an effect on how high you can trim without ventilating.
On some boats, particularly tunnel boats and powercats, shifting the prop aft can also help it maintain a better bite on the water. This is true in many cases where the hull itself causes turbulence, which may cause ventilation in certain situations.
On top of that, being able to control the prop’s depth at any time allows you to lower the drive unit when initiating turns or hopping waves. These are the specific times when turbulent water is most problematic for most tunnel and cat boats.
If your thrust is lined up most efficiently with the boat’s hull and as little of the lower unit as possible in the water, you should see a slight increase in speed. We’re not talking about a dramatic difference here; at best you should expect to pick up a mph or two. Still, in the long run this will save you both time and fuel. And in some cases, such as tournament bass angling, every mph counts.
With the ability to raise and lower the propeller independent of trim and tilt, you now have a much wider range of trim to play with. Trimming the engine up slightly with the motor set as low as possible will have a very different effect on your boat’s running angle than trimming it to the same degree with the engine raised.
Yes, we already covered the efficiency and speed aspects of this ability above. What we haven’t discussed just yet, is how this increased trim range can help you better maximize your own comfort level, in different conditions—a heavy sea state, in particular.
Some boats will better handle those waves with one specific trim angle or another. That best trim angle is likely to change from one-foot seas to two-foot seas, when running bow-on or beam-to. It even depends on wave period.
Every boat will be a little different in this regard, but having a wider trim range allows you more choice when trying to find the best running angle for your boat. So, are you ready to go out and get a jackplate, or insist that the next boat you buy has one?
Good—you won’t regret it. Just remember that to reap all these rewards you need a hydraulic model that can be adjusted underway. Most captains find blinker-style controls (which mount at the steering column) easiest to use. To make sure you don’t raise the engine too high and cause over-heating, most pros recommend also installing a water pressure gauge.
Email Lenny Rudow at [email protected]