Adding Power Trim To A Boat

[Matt’s] boat had a trim plate that could be adjusted by hand. The problem with this setup is that the trim angle of a boat changes as you speed up or slow down. Last year he never really went over 35 MPH because of this issue, but he set out to correct that by adding power trim plates for the upcoming boating season.

The original trim plate didn’t have a hinge on it, but simply flexed when tension was added to the adjustment hardware. [Matt] removed the plate and cut it into three parts; one long thin strip to serve as a mounting bracket, and two plates to independently adjust trim for the left and right side of the keel. Some aluminum strip hinges connect the three pieces, and a pair of used actuators acquired from eBay automate the trim adjustment. Each plate is strengthened by a pair of angle brackets, which also serve as a mounting point for the actuators. The final step was to add a pair of switches near the throttle lever which are used to make manual adjustments when the boat is in motion.

16 thoughts on “Adding Power Trim To A Boat

  1. Actually, the final final step would be to add some logic based on the speed or angle of the boat or something that automatically adjusts it. :)

    But I’m not clear on when it needs to be changed so maybe that wouldn’t work well.

  2. Nice DIY hack.

    Going to hurt when you whack your legs into the brackets getting in/out of the back of the boat. I can’t tell but I hope you deck sticks out at least farther than they do.

  3. The desired setting will change based on what type of activity you’re pulling for, the weight of who’s being pulled, and the weight distribution of occupants in the boat, so it’s probably not something that you could automate very easily. Wakeboarding requires a very different type of wake than barefooting. Too many variables that can be directly sensed to automate it.

  4. Working in this industry thought I’d drop some info. Trimtabs are nothing new. This guy just decided to DIY. A complete set of stainless planes, rams, lines, pump wiring and waterproof dash controls are ~500 bucks for a boat this size.

    Trimtabs are a major control surface and should never be automated. A sudden change in trim could be very dangerous, especially when towing.

    The only computer calculated trim that I’ve seen on the recreational market is from Mercury marine.
    Using a proprietary CANBus style interface branded “smartcraft”
    A gauge polls engine rpm, trim position, speed, fuel consumption numbers and based on previous trips indicates ideal trim position for greatest fuel economy.
    Its great for new boaters who don’t understand how to efficiently run their vessel.

    For towing this same system offers a ‘cruise control’ style throttle system. Towing involves running at the same speed much of the day and this will maintain N speed automatically.

  5. A microcontroller wired to trimtab position feedback and boat speed could do surely some interesting work : imagine you have reached cruising speed. Push a button and the microcontroler does some incremental trim changes, observes speed changes and seeks for max speed (at fixed engine speed). Then put the trimtab position associated to speed in a table. The table with some interpolation can provide data for perfect trimming, including dynamically during acceleration.

    Could this make big fuel savings?

  6. I would be leery of DIYing an automated power trim system on a boat, not something I would feel safe slapping an Arduino in place.
    Say something fails and it is trimmed out wrong and you make a tight turn, your gonna do a barrel roll, and despite what Peppy says you don’t want to do a barrel roll in a boat…

  7. You know, now that you all mention it, I bet once I get some time with these things in place, I will figure out that there are maybe 2-4 positions that i use, and the rest is just travel between them. It should be fairly straightforward to wire up some pre-set buttons. I could be clever and do it with timers, or I could make it easier and do it with an arduino… That may be the future of this project.

    The hardest thing will be knowing where the tabs are at any given time, since they don’t have any positional feedback at the moment.

  8. @Henry
    My concern isn’t with manual trim, but with a poorly thought out automated trim system.
    Such a system would need to include safe guards to prevent the added auto trim form making the boat exceed its’ limits and roll or crash.

  9. You can buy trim position indicator kits for most hydraulic trim tab sets. They are installed inside the ram and protected from the salt water (or fresh in a lake)

    Automating any trim movement IS dangerous.
    If your code or hardware fails you could toss people from your boat, have the person your towing come flying into the back of the vessel, or plow the bow the boat under the water possibly sinking the vessel.

  10. Well, I need to adjust the neutral position a bit, but first trials went well. While I agree that automated trim tabs are probably a bad idea, let’s not get carried away here. On a boat like mine on a lake, there is now way that any of the things you just listed are even remotely possible. The only really dangerous thing you could cause would be a general loss of good handling characteristics, leading to poor control.

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