Outboard trim

[Micky]

Hi, i have a small Vivacity 21. Have just fitted a 8hp Merc outboard to it, not a new one, about three years old in good order etc. However, the boat can make 4.5 knots with the tide max speed, but it feels like the bow is digging in deep, and the engine is working hard to maintain that speed, also using a lot of fuel. so do i tilt the motor up, or has it got to go the other way to level the boat. Or maybe i need to change the prop. Any help please.

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[Talbot]

if the bow is digging in, then try moving the pin on the outboard trim position so that it lifts the engine up by one notch. If you go to far, the bow will come out of the water, and the stern will dig in (but that is better for bad weather anyway). I would have expected you to get around 5.5 kts (assuming waterline length of abt 18.5ft) but no more.

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[tugboat]

I assume you have checked that the cavitation plate on the engine is below the bottom of the transom so that the prop is getting a clean flow of water. Also that the prop is not fouled in any way. If you know what type of boat the engine was used on before that will give an idea if the prop suits your boat - you may need a different pitch. Altering the tilt of the engine may help. You need to adjust so the prop moves aft to help lift the bow.

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