Originally Posted by Heino
Thanks for your note.
I note there was a lengthy FC470 discussion on engine cavitation. You also note the cavitation plate should be approximately 25mm below the lowest point in the middle of the transom.
Does the hi-riders make any difference to the level of the engine mount. I want to make sure to motor does not lift out the water once on the plane.
It's pretty much standard for all Futura-hull Zodiac boats.
The speed tubes will lift the boat out of the water substantially when on plane. The water line on these boats is just a little bit higher than where the material folds over on the bottom of the transom.
Your trim should be level, leaning towards a slight "bow up" attitude. The bow section of speed tube should juusstt barely be touching the water. The water spray should be coming off about 1/3 of the way back from the bow. section of the speed tube.
With heavier loads, the boat will have a tendency to dig the bow in more and your top speed will suffer, but the boat will still plane. Measured with GPS, depending on how much fuel I have left (I have a 12 gal tank on the bow thrustboard), my FC470 stays on plane until approximately 9 mph (10-11 mph with a full tank and two persons). I am running a non-standard lower unit though, so your results may vary.