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I am still trying to figure out this deadrise thing regarding stability. I am going to list 3 boats with stats can someone please explain how stability is affected by degree of deadrise, weight of boat, length and beam. Which of these 3 similar boats will offer the best stability in a moderate to heavy chop. Thanks
Sea Pro SV1900 bay
19'6' 8' Beam
weight 1500 lbs
Deadrise 15
Thats a tough call without a sea trial in each, but I would guess the SeaPro. Same deadrise and weight as the SH, but two inches wider. Sometimes a couple of inches can make a difference. Really I think the two would be about the same. I assume you mean stability at anchor or drift. Although the KW weighs more, the extra deadrise should tend to make it rock a little more. For comparison, I bought a Hydra Sports 2300 Baybolt with 14 deg. deadrise, 23 ft., weighs 3400 dry. 8'10" beam. The boat is unbelievably stable. I sea trialed a Cape Horn 21 offshore with 22 degrees,beam?(I think 8'6"), weighs 2800 dry. VERY nice ride in chop, but rocks WAY more due to deadrise. At the dock you could literally get the Cape rocking with one finger standing on the dock. But there are lots of trade offs for different hulls, and many factors in hull design affect performance characteristics. For instance, my "bay boat" is very heavy with a sharp entry, and with tabs I would say it rides as well as many "offshore" boats with a moderate degree of deadrise, say 18-20degrees or so. Sea trial, sea trial, sea trial...
I'm a stickler for weight in any kind of chop so of the three you have laid before me I would clearly choose the Key West for its deadrise and weight. Plus it's a damn good boat. I have little knowledge on deadrise 101 but I have heard people say if it's less than 17 degrees stay inshore. Now I have know many that were less that went offshore so that didn't say very much.
SomeBODY will give you the gospel according to THT.
By looking only at numbers I would say the Sea Pro is the most stable while the Key West will provide the smoothest ride. Keep in mind that the four measurements you listed are not the only things that can affect a boat's stability.
Of the three manufacturers you are looking at, I am partial to Sea Hunt for the offshore models but I do not think you can beat the Key West for a bay boat. Only problem is that because of its steeper deadrise and greater weight, it will require more water to float.
Weight, beam, and deadrise are three very important factors to consider where stability comes in, but I'd like to offer a little insight beyond those numbers.
Boat manufacturers list beam from the widest point on the boat. Sometimes this number isn't a good representation of the stability of the boat though. It's far more important to measure the beam at the water line since this is where it matters, but this figure is practically never offered.
Take the three examples above, the Sea Pro, Sea Hunt, and Key West. It would seem that the Sea Pro and the Key West have the same beam, but the waterline width is drastically different with the wider beam here going to the Key West. This being the case, it's entirely possible that even with a steeper deadrise the Key West could be more stable at rest while still giving a better ride. I do not know this to be a fact, but I do know it's possible.
Also, another important consideration in a bay boat is draft, since it is an ihshore design. The waterline width is one of the most critical measurements to predict how much water it takes to float a boat, and all the people and equipment that we put into one. The boat has to settle down into the water displacing the equivalent weight in water. The wider it is where it meets the water, the less it has to settle down. Therefore again, it's possible for the boat with the steeper deadrise to take less water to float than one with a flatter bottom if the flatter bottomed boat is more narrow down there at the waterline.
Now for how weight affects stability. The more mass there is to move the more stable that mass is. Newton's law, sort of. Take a little twelve foot john boat. If you're in it by yourself, no motor, and little gear it's fairly tough to stand up and take a leak. Now if there's a big ole bubba in the other end sitting down it gets easier to take care of business because his mass resists quick movements. A heavy boat has the same effect.
I'd suggest boat shoppers take a tape measure with them. Measure and compare waterline widths of the boats you're interested in. The results can surprise you.
Like I said, a sea trial tells all. Numbers and opinions and experience only tell you so much. I have been suprised on several sea trials with assumptions based on numbers, sometimes for the better and sometimes for the worse.
Deadrise and stability in Bay Boats? 
