Thank you Capt. Terry. Great info and I'll be sure to do my calculations before hanging anything on the transom.

KNZ911 - Thank you. Will do!

Predicting CG changes
 

You are most welcome. I suspect others have been intimidated by the math or just decided to wing it. I made it as simple as I could- just plug your numbers in for mine. Certainly should be better than guessing. Best wishes and looking forward to results.

Having a base CG is a great starting point but you have to carefully consider all weight that will be in the boat and to compensate appropriately. The CG on a 23' boat can change drastically with things as simple as an extra person, cooler, ice, gear, livewell (empty/full) and fuel level at any given time. These factors need to be considered into the equation.

On almost all CC rebuilds the boat ends up bow lite and has to be addressed post build. I would push fuel as far foreword as possible and put the fishbox up in front of the console. Nobody is going to riding up front on a CC unless it is dead flat so count on that weight as well.

You should also consider what Don has suggested and go with a big single. Less weight, cost, less drag, 1/2 the maintenance and better performance per pony. If you are dead set on twins you should be planning on moving the whole console forward.

Not sure where the line is for the size of boats that really need twins, maybe 26'/27'+?? My opinion, with the dependability of today's outboards a 250 - 350 hp single on a 23' SeaCraft is the most efficient way to go. Now thirty, thirty five years ago dependability was not one of the outboard manufacturer's strong points.

Wish I had taken a picture last time I was at Nags Head, but, my buddy's neighbor redid a 23 cc last year and put twin 2 strokes on a bracket. Can't remember what size, but at least 175's. Anyway, he had the bottom sprayed white and the waterline at the stern is only about 16" from the cap...ON A 23!

Don, I don’t know what you’re talking about. My old girl was right at home 120 nautical offshore on the west end of the Middle Grounds as long as you had 30 jugs of extra fuel and 5 gallons of smoker oil. What could go wrong?

Yes Sir Moose......a boat's fuel tank vent hose is normally 5/8", these old V-8 OMC's were the only engines I know of that needed a 5/8" fuel line to feed the monster. Plus it was cost effective to buy 2-stroke oil by the 55 gallon drum....30 gallon drum minimum :) :)

Capt. Terry -

So... I used your formula and came up with a CG shift of 1.15 feet back towards the stern. The only variable I changed was the I/O engine to dual outboards. I haven't played with fuel tank size or location yet, or the battery location either. I am also waiting on a spec sheet from Armstrong for a dual engine bracket so I know exact weight of bracket. Would also be nice to know how bracket floatation will affect CG.

Going to dual outboards appears to only add 150 lbs. to the boat. Hopefully that 1.15' shift in CG won't adversely affect how the boat sits in the water. Or...hopefully with a little more engineering I can trim her out nicely while keeping the deck dry and the scuppers draining.

What outboards are you looking at?