1970 Seafari conversion to CC

Bushwacker · #11 07-25-2014, 10:51 AM

Quote:

Originally Posted by flyingfrizzle

With all that weight of a 4 stroke, 150 lbs bracket and 175 lbs of live well water you will need to move it about a foot or two in front of the boat.

Frizz is about right! A Seafari like you started with is about 400 lbs heavier than a CC, and most of that weight is up front in the form of the bulkheads, cabin top and door, windshield, bunks and anchor locker bulkhead. So far you have removed all of that, and now you're talking about running a motor about 75 lbs heavier than mine, PLUS adding another 175 lbs of water right at the transom! You've done everything possible to insure a stern heavy boat that won't plane below about 25 mph!

The CG on my boat is about 6.5' fwd of transom. That location is real obvious because the aft cross member on my EZ Loader roller trailer pivots, tilting the boat about 30 degrees when the CG passes over it. My boat is a stock Seafari with a 34 gallon tank plus 2 batteries, a 1.8 gal oil tank and a 9# anchor + 6' of chain +100' of line in the stern, and a 9# anchor on bow with 20' of chain and 300' of line in anchor locker. Motor weight is 427 lbs and bracket is a 30" Hermco; not sure of bracket weight but I'm guessing it's somewhere around 150 lbs. You could use those numbers to set up a moment balance about the current CG to solve for the CG location of the bare hull (assume it weighs about 1100 lbs). Once you have that you could then subtract the moments for the stuff you've removed and add the moments for your heavier motor, live well, gas tank, and console, etc., to figure out the new CG.

I would strongly suggest using Coosa in the new transom and some sort of composite in the deck in the rear of the boat and maybe plywood in the front of the boat to make it a little less stern heavy. I'd also try to minimize setback on the bracket; Don Herman said he can make his with 18", 24" or 30" of setback. I'd also put that livewell in the front of the console, assuming there is enough room for it up in the bow of the boat!