hydrofoil outboard cat performance improve powercat

On a cat, hydrofoils can reduce side to side rocking while cruising.

Will adding a hydrofoil improve the performance of your boat? I get asked this question all the time, usually by people who have outboard powered boats with relatively lackluster performance. And I always start my answer by cautioning that every boat is different, and there are no guarantees. That said…

Adding a hydrofoil to an outboard does provide a performance boost much of the time. The smaller the boat the more significant the impact is, especially on boats that don’t have trim tabs. On a 16 footer with a mid-sized outboard and no tabs, for example, a hydrofoil will usually level out the ride by forcing the stern up and the bow down, and will end or greatly reduce porposing. There is a performance boost, usually of two or three MPH at cruise, as a side-effect. In other cases, specifically with powercats, foils will reduce the side to side rocking motion that often accompanies a beam sea. The picture you see here is of my own boat, a 22 Glacier Bay. When I added the foils side to side motion dropped in the 10 to 15 percent range. What about a performance boost? No dice; in this case speed remained identical to foil-free operation.

Should you add foils purely to get a speed boost? Probably not. Although there are a lot of claims – mostly by the foil manufacturers – of speed boosts, in my experience if there isn’t another performance problem the foils solve (like the trim issues) then speed remains the same.

Of course, many people want to give a foil a try but hesitate, because it means drilling holes in the anti-ventilation plate. But check out Sport Marine’s SE Clip, which allows you to mount Sport’s hydrfoils without drilling. It seems impossible that these clips can actually take the torque and hang on to the lower unit without any drilling, but I tried ‘em on the Glacier Bay and both have held on tight without a problem. One caution: the installation instructions seem to have been written by a chimp, and you’ll feel like Bobo yourself when you try to put these things on. It took me a solid three hours to figure out how to do a 15-minute job. Meanwhile, if you’re confident the hydrofoil is a must-have, traditional drill-and-bolts like those from Dolcher and Stingray work quite well. So back to the question – should you put one on your boat? Only if there’s a problem like those mentioned above which you’re trying to solve. If your boat already performs well, however, you shouldn’t expect these things to work magic.