A buddy of mine bought a boat a while back that couldn’t keep its nose planted no matter how much negative trim he dialed in on his outboard. Hit a wave, the bow would launch. I think his solution was to haul all his bait, coolers, and as much gear up there as he could — until he eventually put the boat up for sale. He liked the boat, but he hated the ride.
About a month went by, and as I was walking past another boat like his on a trailer, I noticed it had aftermarket trim tabs mounted on the transom. As I recalled, all my buddy’s had on its transom was an outboard motor. That was the “aha” moment. Trim tabs. It made perfect sense. I called him immediately.
“Dude, don’t sell your boat,” I said. “I can fix it.”
“I know, I know, your dad’s a TV repairman. He’s got an awesome set of tools,” he said. “That joke is getting old.”
“No, really!” I shot back. “You need trim tabs. There’s a boat here in the marina just like yours and it has them. Yours doesn’t. That’s why it rides so terribly.”
Of course he didn’t believe me, so he came right down to the marina. It cost him some time and a couple of gallons of fuel, but he pulled his boat off the market and we set about figuring out how to install trim tabs.
We looked around a bit. Lenco, Bennett, and Mercury Marine all offer something. Mercury’s are the most robust, but the Lencos and Bennetts cost less. Pick what you like, but be sure you mount them correctly.
First, I’m a big fan of through-bolting, and if you can mount at least two of the bolts that attach the trim tabs to the transom that way, do it. I think the Mercury tabs are designed to be through-bolted when the boat is built, but the Bennett and Lenco tabs use lag screws to attach the bracket the transom. Use a sealer or an epoxy around the holes whether their through-bolted or screwed in.
Second, mount them about half inch above and parallel with the running surface, as far outboard as you can. They need to be a half inch higher so they don’t create drag when in the up position, which can decrease fuel consumption and create odd handling. They also need to be mounted parallel to the running surface so the whole tab touches the water when you lower them. They’re more effective that way.
Long story longer, my buddy kept his boat because using just a hint of tab kept the nose down in choppy conditions. Fuel consumption wasn’t affected, and he didn’t have to go through the long, drawn-out process of shopping for another used boat.
Come to think of it, he never thanked me, and we used my tool set. Which is, in fact, awesome.
This video from Bennett trim tabs will walk you through the process. All you need is an awesome set of tools.