Terry - I made your post a sticky a few years ago in the repairs section. I'm not putting my head in the sand and disputing math/physics, but I think the additional stern weight and LCG shift (of 1ft) is significant and very noticeable. Sadly I can only offer my own anecdotal evidence
(which doesn't mean squat) from running the 20 seafari w/ bracket and 20ma with transom mount outboards. Adding 100lb kicker to the transom on the 20MA was noticeable. When the 20 seafari's inspection plate on the bracket leaked and the tub filled with water that was also very noticeable. The extra weight on the transom and changes in the running angle at lower speed could be felt (or were reliably imagined.
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Bushwacker comments from the post.
Quote:
Originally Posted by Bushwacker
That's what I learned over 10 years ago when I replaced a 300 lb motor on the transom with a 427 lb motor on a bracket, and have been trying to tell folks ever since! The resulting CG shift makes a big difference in the boat's low speed planing performance, and ride when it gets rough! Fortunately, the Seafari's big cabin makes it easy to put a lot of gear up front when you're making a long trip. I even installed pad eyes on the bulkheads so I could keep it all tied down in rough seas!
Do you have trim tabs on your boat? They will help compensate for load/CG shifts. A 4B prop will also give you more stern lift as will an SE Sport hydrofoil on the AV plate.
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I do appreciate your post that shows how to calculate (and compensate) for the LCG shift. Maybe someday I'll write a matlab program with some strategically placed sensors and sandbags to add some more "science" to this discussion.
p.s. - I ran a different prop for part of the fishing season. Thank you!!
