Quote:
Originally Posted by Adam
You are probably totally correct if conditions are flat calm / perfect sea - However as soon as waves are introduced by running the engine further back the prop is more often in water that is less effected by the transom re-entering the water / breaking water flow. So in a dynamic situation there are gains to running the prop further back and I imagine that this is what has been called 'cleaner water'. Not a massive difference but one none the less.
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Having the lower unit further aft, would indeed have a different effect when it roughs up, the ability to control the height of the drive in the water flow, is non existant, and with a significan't amount of setback, every time the boat kites, or lands at all stern down, you dig a dirty great hole with ya lower unit out on limb, causing loads'a drag, and if the power aint kept on, a nice 'brake' to intiate rotation into a stuff. So appendage drag is gonna be all over the place, especially if you dip the drive low enough in the flow to to go above the streamlined portion of lower unit. I would think this would be far more of an issue with a traditional V bottom, as they're generally less stable in pitch than a stepped boat.
I believe, the further away from the transom, the messier the water (obviously up to a point where it begins to settle, but I reckon that 10's of meters behind the boat)
The only advantage I see of setback, is to increase the leverage for out trim, and moving the C of G aft, both of which will only benefit max speed in flat water.
It also means getting on plane will be easier, as the motor will dig deep at lower speed, so kinda automatically increase the drive height as speed increases, which I think was the thinking on the original 'Gill Brackets'.
I can see the advantage of being able to lift & drop the motor, but you can only usually have this, at the expense of having setback. again, this seems of more advantage with a pitch stable boat like the B23
So, for stepped bottoms, setback could be a good deal, but for non stepped V's, in an offshore situation, I reckon the advantages are hard to see, but the disadvantages are obvious.
JMHO and of course I aint a designer, so probably don't know jack.