How to trim your boat
Knowing how to trim your boat (or adjust the angle of your bow) can improve your boat’s performance in the water.
Most boats handle best when running on their lines, or parallel with their at-rest waterline. A slight bow-up trim increases a planing hull’s efficiency, but don’t overdo it. Excessive bow-up trim increases slamming in a chop and reduces your forward visibility.
A little bow-down trim gives a more comfortable ride and better steering at slow speeds or in a chop, but it can also increase spray and cause bow steering or bow burying at cruising speeds in following seas.
Trimming your drives
Outboards and sterndrives typically provide a powered adjustment for the drive unit’s trim angle. When you trim the drive out (away from the transom), the bow rises. When you trim the drive in, the bow falls.
Generally, you trim the drive in for steering, visibility and wave-handling at slower speeds unless you need some bow-up trim to counterbalance weight in the bow. Drive-in trim also helps you accelerate to plane by lifting the stern. Once on plane, you probably want to trim the drive out, but if you go too far, the bow may begin to porpoise up and down; trim the drive in until this stops.
Using trim tabs
A trim tab is a hinged plate mounted at each side of the transom’s bottom edge. When a tab (or flap) is in the raised position—flush with the bottom, it has little effect. When it is lowered, it lifts its side of the stern and depresses the opposite bow. The flap’s angle is controlled hydraulically from a pair of rocker switches at the helm.
Because each trim tab can be controlled separately, you can adjust both side-to-side and fore-and-aft trim. When both tabs are trimmed down, the stern rises and the bow drops. This can be essential for getting an inboard boat to plane and can also augment a trimmed-in outboard or sterndrive.
Once on plane, adjust the tabs to suit. Raise them to decrease drag, keep the bow up in a following sea or fall off plane again, and lower them slightly to maintain planing at a lower speed or reduce slamming in a chop.
If your boat is unevenly loaded, you can level it side to side using one trim tab. Similarly, if you’re heeling into a crosswind, lower the tab on the side of the boat you want to raise. Do it incrementally, so you can gauge the trim’s effect before lowering the tab further.
Feel at home on the water
Learn to boat with confidence by taking the Boat Handling course online from America’s Boating Club.