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Finding Your Boat's Proper Trim

Find your boat's proper trim for best running attitude.

Proper trim (he looks to have it right) optimizes fuel efficiency while maintaining a safe, comfortable ride.

Many things can affect the performance of your boat, but one that's consistently underutilized is proper trim. Running at the right attitude will increase your speed, reduce your fuel consumption and greatly improve the comfort of your ride. The angle at which your bow meets the water and waves has a direct correlation to how efficiently you operate your vessel. In many situations, improper trim can be a safety concern as well. Getting the running surface of your hull to have the least amount of wetted surface (drag) will increase your efficiency and should be your goal most of the time. But, in some cases, it's actually better to have more of the hull in the water to allow your bow to knife through the waves. It's dialing in the “sweet spot” that is so important. Understand that it's a moving target as conditions change.

Trim tabs, which are installed on many saltwater fishing boats, can help you to fine tune your running attitude by creat- ing lift at the stern, allowing the boat to run higher and reducing its foot print. The two independently adjustable metal plates at the transom are controlled by a switch panel at the helm and can also compensate for a hull running with a list due to engine torque or unequal weight distribution.

When you're running into a head sea, it's best to let the bow come down and give the entry of the V a chance to slice into each wave. In a following sea you will want your bow high, out of the water. Either riding the back of the swell or overtaking them, you don't want to allow your bow to stuff into the backside of the wave in front of you.

Adjusting the attitude of your hull means ad- justing the trim angle of either your engine/out- drive alone or by use of trim tabs or a com- bination of both. What you'll soon find is that small adjustments can have a big effect and something as simple as a passenger mov- ing from one side to another or up to the bow may require you to counter that change in weight distribution. On some boats, it may be best to run a full- down trim to get the hull to plane off, then immediately trim up as the speed increases. So now that you want to adjust your boat's trim attitude, what are some of the indicators to guide you and how do you do it?

To start off, look at the spray as it exits to either side of the hull. If it's too far forward that tells you the bow is plowing through the water, which can cause the boat to bow steer and have poor fuel economy. If the spray is too far back towards the transom, unless you are running a bass boat, your bow is too high and a percentage of your thrust is being wasted along with exposing the bottom of the hull to impact waves for a rougher ride. Once you have established what you feel is a good trim attitude, you can fine tune it or “dial it in” by using your RPM gauge plus GPS and fuel flow gauge—three pieces of electronics once considered luxuries but now installed as standard equipment on most boats. Once you have reached your desired speed, whether it's cruise or wide open throttle, and feel you have the prop- er attitude, adjust your trim angle while watching your RPMs, speed and fuel con- sumption to get the best performance.

Trim adjustment for either your out- drive or outboard is normally controlled by a rocker switch(s) built into the throttle control handle. Trim the engine/outdrive up and the bow rises—too much, and the hull can porpoise and the props aerate or cavitate. Down trim can lower the V entry of the hull into waves to soften the ride— here again, too much and you will plow through the water. Proper drive trim keeps the thrust generated from the propeller as parallel to the water's sur- face as possible.

So if you're looking to improve your boat's efficiency and ride all you may have to do is adjust your attitude... running attitude.- FS

First Published Florida Sportsman May 2013

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