How to Properly Trim a Sterndrive | Boating Magazine

How to Properly Trim a Sterndrive

Learn how to properly trim an sterndrive and provide a safer, smoother ride.

When we get mail on boat-handling problems, the bulk of it sounds like this: "When I do this, my boat does that and I can't make it stop." Sometimes the problems are mechanical and sometimes, well, they're just operator error and as easy to correct as pushing a button — literally. This is how properly trimming an engine's outdrive can eliminate pounding, porpoising, wandering and sluggish speeds.

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: My boat pounds into the waves, often taking water over the bow.

Cause: You could just be going too fast in rough water, or the propeller might be trimmed too low, driving the stern up and the bow down.

Solution: It's possible your hull has developed a "hook" or a concave bottom that causes the bow to ride low, but more than likely, your trim is out of adjustment. Start by pulling your trim tabs up fully (if you have tabs). Then trim the propeller up with the trim switch on the gear shift/throttle. Do it a little at a time until the ride improves.

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: My boat leans to the left at planing speed but is level at rest.

Cause: Prop torque (the twisting force that the prop creates as it turns in the water) can cause your boat
to lean.

Solution: Adjusting your trim upward will often correct this issue. In the short term, adjusting your crew to counterbalance the force can be helpful. The best solution might be to add trim tabs to your boat if you don't have them, and adjust them to level the load. Visit bennetttrimtabs.com

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: I trimmed my engine, but the boat still pounds the waves too much.

Cause: V-bottom boats usually have a very sharp stem — the point of the bow — to slice the waves. The bow might still be riding too high to cut the chop.

Solution: If you have adjusted your prop trim, chances are that your trim tabs (if you have them) are not properly adjusted. Or, you simply might be going too fast for the water conditions. Slow down, check your prop trim, then start putting the tabs down gradually with one-second taps to the control buttons. Experiment to find the optimum ride.

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: My friend, with an identical boat and prop as mine, gets 2 more miles per gallon in his boat than I do in mine.

Cause: Assuming your engine is running correctly, you need to remember that boats get different miles per gallon depending on the speeds, trim settings and loads.

Solution: Set your boat's RPM at your friend's favorite RPM and see if your speed is the same as his. If your speed is lower, adjust the trim upward until your speed improves. Adding a fuel-flow meter will give you surprising information on the most economical speed (cruising speed). He might have found the sweet spot; you have not. Visit floscan.com

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: My boat leaps up and down on the water like a porpoise.

Cause: You could have a hull flaw that causes this, or your boat's propeller trim could simply be set too high, causing the bow to lift, then fall.

Solution: Trim adjustments should be made to keep the propeller pushing on a level track as the boat's running angle changes with the speed. Trim the boat all the way down and as it accelerates, gradually trim the propeller up. At proper trim, the boat glides over the water without porpoising — which is what the bouncing effect is called.

How to Properly Trim an Outdrive

How to Properly Trim an Outdrive

Cameron Thorp

Problem: My boat pulls hard to the side when on plane.

Cause: Prop torque pulls the wheel. There's a trim tab over the prop to counteract it. It also doubles as a corrosion anode, and it might have corroded away.

Solution: Replace the tab if it is gone or damaged, and then through trial and error set the tab for a neutral "pull" at your favorite cruising speed. Trim the prop while underway. On newer boats, no-feedback steering systems hold the helm in place and reduce the feel of the torque. Visit teleflexmarine.com

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