How to Trim your Boat Right, Every Time

Finding the right trim when running a powerboat has two major effects: it will improve the riding characteristics, and maximize fuel economy. Yet many boaters never even bother to adjust the trim much beyond trimming down for the hole shot, and up when on plane.

trimming a boat

Find the right trim setting, and you'll be more comfortable while burning less fuel.

Why do so many boaters ignore trim? Because they don’t realize just how big an effect it can have. A few years back I was invited on a 24′ walkaround for a 20 mile journey, to an area that had been thick with cobia. But it was so rough, half way into the ride we slowed up and discussed turning around. I had noticed that the guy running the boat hadn’t touched the trim tabs once on the entire ride, and suggested that instead of turning around, he let me take the wheel for a while so he could rest. At the helm, a few tweaks of the tabs changed the ride from painful to merely uncomfortable. We made it to the hotspot, and in short order hooked up with a 60-pound cobia.

Another example of the importance of trim can be found in fuel efficiency. During the past 15 years of testing boats (well over a thousand, just for the record) I’ve compared fuel burn rates with and without trim set properly, several times. As a general rule of thumb, for every 10 GPH of fuel burn, trim angle will account for 0.1 to 0.2 GPH. One or two tenths of a gallon an hour might not sound like much, but if you put 100 hours of running time on your boat in a season, that’s 10 to 20 gallons of fuel. Would you ignore someone if they offered you 10 or 20 gallons for free, and all you had to do was flip a switch now and again? I didn’t think so.

So, what exactly is the secret to finding the perfect trim? Understanding that in each and every sea condition, it will change. There IS NO perfect trim angle for any individual boat, in any specific sea condition. Rather than finding one trim angle and sticking with it, you need to constantly adjust those tabs and/or engine trim. And not just once during a run, but sometimes every few minutes as the sea conditions or your direction of travel change. In fact, if you haven’t played with the trim after a change in direction or a half-hour or so of cruising, you should  mentally remind yourself to give it a shot. Tweak it and change it back and forth until the ride feels best underfoot, and you’ll probably discover that the “perfect” trim is just a few adjustments away.

5 comments

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  1. Mike

    Lenny,
    Thanks for another useful article. I’ve been boating fairly regularly for about 10 years or so–95% saltwater. I tend to set the trim on smoother water by trimming down just below where the porpoising stops. Is there anything wrong with that approach generally speaking? On rougher water–like offshore–I struggle quite a bit more with that. I don’t have trim tabs and currently run a 24′ deep hull boat with a single 200hp. Any recommendations on setting trim in those rougher conditions? It’s hard to gauge what feels more comfortable in situations like that.

    Thanks again.

    • LRudow
      Author

      Sounds to me like you’re on the right path and I think you’re right, the rougher it is, the harder it is to figure out where the trim’s best. As a rule of thumb try getting the bow down a hair more than usual in the rough stuff, that usually helps a deep-V run smoother. Again, the best thing you can do is keep adjusting and changing, and feel for the best ride.

  2. Thad

    16 ft flatbottom- 60 hp w/jackplate 6″ up/ 6″ back, fishing is inshore so trim is mostly for smooth fast run and fuel economy. Too much bow down boat plows, too much bow up hull wallows. Both condition are high in “drag” and can cause awkward handling.
    By using tach adjust trim to angle that gives the least resistance to run. Bring throttle up to speed then adjust trim without changing throttle setting watch RPM for gain or loss. Peak RPM is the point of least resistance water to hull. Usually this is just before porpoising.
    With high jackplate in tight turns necessary to trim bow down to prevent outward roll keep hull flat.

  3. Mike

    Lenny,

    I’m hoping you can give some advice, as I know there is likely not an absolute answer to this question. I’m considering buying a different boat, but the hours are a bit high on the 2001 Merc 2-stroke 225′s–about 1100 and 600 respectively. I’ve got reason to believe they were well maintained. I never thought I would consider a boat with hours this high. I would have them gone through by a mechanic before closing the deal, but I would appreciate your thoughts. Should hours this high make this a “no way” boat?

    • LRudow
      Author

      Based on hours alone, no, I wouldn’t consider it a no-way deal. Plenty of outboards will run for plenty longer; I’d base the decision on the condition they’re in, and how well they’ve been maintained. (On hours over 1,000, I would for sure want to see the maintenance records, tho!)

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