How to correct sterndrive trim problems

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When chatting to other sterndrive boaters, questions often pop up about anomalies associated with incorrect sterndrive trim. There are usually two main issues that come up in discussion. Either it’s operator error or it is the incorrect mechanical setup of the boat that is hindering its performance. With the latter, often it is simply getting the correct trim methods right which will eliminate problems such as sluggish speeds, porpoising, wandering and pounding on the hull. Here are 5 solutions to sterndrive problems encountered by our readers.

Hennie van Aswegen writes: My boat tends to pound into the swell and waves and often takes water over the bow. How can I stop this occurring?

The cause of such a scenario is often too much speed, particularly in rough water. Alternatively, the propeller could be trimmed too low, which will drive the stern up and the bow down. The most likely solution is your trim is out of adjustment. Begin by pulling your trim tabs up fully if you have them fitted to your boat. Now trim the propeller up slowly until the boat’s ride improves.

Marcus Garvey writes: When I reach planing speed my boat leans to one side. Before the boat reaches planing speed it does not lean. Why is this happening?

The usual cause of boat lean at planing speed is propeller torque. By adjusting the trim of the boat upward, it will often fix this problem. A quick fix is using the crew’s weight as counterbalance. A permanent solution is to add trim tabs to your boat.

Chippie Olivier writes: My boat still pounds the waves even after I trimmed my engine. Any ideas how to correct this?

Most V-bottom boats have this sharp V to cut through the waves. In your case the bow might be riding too high in the water to be able to cut through the waves and chop. If you have adjusted the trim of the prop, there is a good chance that your trim tabs are not properly adjusted. You might also be going too fast. Try slowing down and letting your trim tabs down in short increments. Find the best balance you can with a bit of experimentation.

Mike Hepburn-Brown writes: A friend of mine has the same boat as I do – it even has the same size engine – but he seems to get better consumption figures on his boat. Any ideas why this happens?

Consumption figures are dictated by a variety of scenarios. Boats are never the same weight as they carry different accessories, fish boxes and even passengers, so it is difficult to compare the same model boats as their weight setup might be very different. Try and test the boats together by setting the RPM at the same level. If your speed is less than his boat, try adjust your trim up until you match the speed of the other boat. Your friend might have found the sweet spot on his boat, you just need to find yours. Fitting a fuel flow meter will also tell you what your most economical speed is.

Jimmy Smith writes: My boat porpoises up and down on the water. Do you have any suggestions how to stop this?

Porpoising can be caused by a flaw in the hull construction or even damage to the hull. Alternatively, your boat’s propeller trim is set too high, causing bow lift and fall. Make your trim adjustments to keep the propeller pushing the boat on a level track as the boat’s running angle changes with the increase in speed. Trim the boat down during the acceleration process and then gradually trim up. At the correct trim there should be no porpoising.

Correcting Sterndrive trim issues
Correcting Sterndrive trim issues
Correcting Sterndrive trim issues
Correcting Sterndrive trim issues

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