Braket build

martin · #1 10-06-2012, 09:52 PM

Hi guys what are the set backs for the brackets 27" 28" 30" i have a120 johnson.. Would like to be able to upgarde to 150-or 175 in future... What would you all recommend for my 20sf..oh and i cam up with about 12-13degrees transom angle

Bushwacker · #2 10-06-2012, 11:23 PM

Brackets create a big CG shift aft, so best to minimize both setback dimension and motor weight, and get a bracket with maximum flotation (Hermco) to have any chance of it being self bailing at rest. Don said he can build his brackets with setbacks of 18, 24, and 30 inches. Also consider moving console and fuel tank forward as much as possible. Min planing speed and ride will also take a hit, so plan on running a 4B prop and maybe a fin on AV plate to get more stern lift.

martin · #3 10-06-2012, 11:33 PM

Calculating bouyancy and size of bracket with 30" set back and getting something like 525lbs of boyancygive or take.. But with moter and 40 gallon livewellabout 12" in front of transom.. I am negative about 475... I do have trim tabs.. Shoukd i build bracket with max lift and then start placing tank console and coffin box in... Or maybe put some weights in the hull and see where things need to be.. Thanks for the reply bushwacker

Bushwacker · #4 10-06-2012, 11:56 PM

The flotation at rest isn't nearly as important as balance and performance up on plane. When you're up on plane with the tank out of the water, the boat will still know you shifted it's CG aft by about 18" or so! A 40 gallon livewell near the transom doesn't help either. I'd suggest putting it forward of the CC.

When I repowered from a 300 lb motor on the transom to a ~420 lb motor sitting 30" further back, my min planing speed went from 12-13 mph to the low 20's and that's with trim tabs! And the Seafari has more weight forward than the CC to begin with. I finally got it back down to 12-13 mph by going to a 4B prop and a fin. Don't know how fast you want to run or what sort of seas you run in, but if you're running offshore in seas of 3' or so, 120 hp is plenty of power for a 20. Ran mine for over 30 years with a 1975 "115" (crankshaft hp) that really only put out about 90 hp at the prop. Cruise speed on Bahama trips with very heavy load was about 20 kts, but it rode very well and I could hold that speed in seas up to about 3'. I couldn't use much more power in those conditions, so you might want to try it with the 120 first!

martin · #5 10-06-2012, 11:49 PM

I have lightend up the hull alot as i have removed the platform and all wood but replaced transome and keel with compound at 40 lbs a 5 gallon miss calculated the transome so that is about 200 lbs keel is 40 lbs , top cap added about 50 lbs hull sides about 80 lbs... Floors are going to be about 70 lbs.. And 60 gallon tank up front... Put hull in water and she floats high bow heavy and water levelabout 4" below chine..... I am going to build bracket and install on boat with out platform to see where it needs to ride... I wish the transom did not endup that heavy.. But it is waht it is.. It is a 73 sf with large stringers do i need to raise floor 2" for self bale out the stern

martin · #6 10-07-2012, 12:38 AM

Baitwell forward will that beat the bait up .. Did notnwant water splashing in my face other then spray from bow

martin · #7 10-07-2012, 12:42 AM

3' is about all i want to fish in.. Would like to run about 28or so... I can make the live well smaller

gofastsandman · #8 10-07-2012, 09:23 AM

I have my livewell under the leaning post. loves the weight there. Mind you my boat is an `89 and I "think" the deck may be higher. This is all factory. 25 " trasom, scuppers out the transom, and self bailing w `96 150 rude @ 375lbs.

Anyone know if the deck got raised in the late70s or 80`s?

Cheers,
GFS

Bushwacker · #9 10-07-2012, 01:04 PM

Potter had raised the deck by an inch or two on the Seafari by '76 and probably did it on other 20' models as well. He may have done that as early as '73 when he changed stringer configuration from 4 individual hollow pre-molded stringers to the 2 box stringer configuration. A friend of mine bought a new Seafari in '76 and the little wells around the scuppers that are about an inch deep on mine were about 2-3" deep on his. His boat also had the bigger 50 gal fuel tank, the smaller step down that was just big enough to open cabin door, and front of windshield was moved forward about a foot with a fixed section of glass below the opening section. It also had storage box on passenger side just aft of windshield similar to the 23 Sceptre.

martin · #10 10-07-2012, 01:40 PM

Yea i just struck a line across deck and bow 2 inches and the Freeboard is 17 inches from that line.. not much to keep you inside.. I did not draw lines on the outside when she was in the water..before teardown.. Would have liked to get a starting point.. I just cannot see this boat at rest displace that much more water. I pulled old picts of the boat in the water with some gear. and it rested at about one inch above chine in the stern...I am going to leave it the way she is Although I will have trouble killing the deck into the forward area as I start to get into the chine.... I will probably bring the upper bow gunnel back some about 15 inches and get more area to stand on and throw 10ft cast net.. then killit itno the deck.. That way i will have more anchor storage. as well.. here are some pictures .. You can see a good scum line on the hull. I will just keep it a 1" above the stringers. Building bracket first and attacing to boat then loading with parts to see where I need to be with weights and all. Thanks for the help...