20ft SeaCraft With Twin V4's??? Just Thinking OL..

[Dunk]

dunk ther was a 20 with twin merc2.5s on it down in the keys a few years ago. It sat real low of course and i saw it listed in the boattrader about a year ago. also in the potter years they would factory rig twin 70 hp hope this helps

Now we're talking... I don't know how long ago you are talking about, but when I was living in the Keys in the late 80's there was a 23 in Islamorada with a pair of 2.5 Bridgeport Offshore 260's. I was running one of the headboats for Robbie at Holiday Isle on the night trips. I was coming up Rt1 just at the end of Lower Matecumbe at the Lignumvitae Key channel where it runs from Robbie's up to Papa Joes along RT1. These two guy's had just run the wheel ditch up behind Matecumbe and were lining up to run up to Papa Joes. I was pacing them, speedometer in the truck was reading 80mph and that 23 Seacraft was walking away from me.
You have to see that boat run to believe it. I never did see that boat again. I'm not sure if he was local or not.

I've seen some wild rigs built once you put USCG regs behind you.. Even a 75mph+ 20ft Whaler Outrage with a pair of 175 Evinrude Ficht's on it.

Finster..as you guy's get to know me you'll find that I'm dead set against bracketed outboards. Unless the boat was designed from the mold up to handle the engine(S) 30" behind the hull most don't run the way they should. I think it's an especially bad idea on seacrafts because you are putting the best part of the wave cutting deep vee in the air where it won't do you any good. Yes, patching up an old stern drive with a bracket for an outboard is good way to save the boat because you are removing a 1000lbs of sterndrive and engine. Boats like that were designed to handle the weight on the transom. My next rule is nothing under 23ft get's a bracket. Moving the engine 30" behind a boat like 20ft Seacraft that was never designed for it, I think is foolish just to gain a little space in the rear of the boat. There's too much "Notched Transom" fear running rampent on the internet. The biggest reason boats sink from water over the transom is not keeping your deck access plates water tight. 90% of the boats I survey I find bad orings or broken access plates that will let water flow into the bilge.

[gbf03]

Dunk
In Ft Lauderdale there is a potter built 23 with twin 250 yammis on it.

[strick]

Finster..as you guy's get to know me you'll find that I'm dead set against bracketed outboards. Unless the boat was designed from the mold up to handle the engine(S) 30" behind the hull most don't run the way they should. I think it's an especially bad idea on seacrafts because you are putting the best part of the wave cutting deep vee in the air where it won't do you any good.

I'll call you out on this one dunk [img]/images/graemlins/wink.gif[/img] While I agree with you that the boat must be properly designed or structurally capable of holding the motor on a bracket I disagree that it changes the running surface and puts the wave cutting portion of the boat too high in relation to the water. At rest a good bracket provides enough flotation to offset the center of gravity difference. It may take a bracketed boat a second longer to get on plane then when before it was bracketed.....but once on plane the running surface/water contact area should be virtually the same. Here are a couple pics of my boat before and after the bracket. Looks like I actually gained a little flotation. I also have some running shots that show the boat is riding pretty close to where it was when it was a notched transom. I dont have a way of loading them right now because this computer does not have the right software.





Strick

[Trayder]

Strick-

Was the first picture taken in Freshwater and the second in Saltwater?

[strick]

They are both taken in brackish water within a mile of each other. The first pic has the kicker and me for added weight and the boat does look like it's sitting really low. The kicker probably made it tilt a little to the starboard side.

I've had two bracketed boats and the only diffeence that I noticed before and after is that the boat handles like it's 2.5 feet longer. Ride is the same or better.

Strick

[strick]

Heres a couple pics of my first test drive with the bracket and a short clip of Capt Chuck's boat getting it on. Compare the running surfaces of the bracked boat vs the non bracketed boat. Both boats are at cruising speed 30 plus MPH.

http://www.casdvm.com/photos/gettin%20it%20on.mpg





Strick

[Fr. Frank]

Dunk is right, and so is Strick. It depends upon the hull, and especially on the amount of rocker in the hull. In a previous life, I spent some time as a test pilot (strange name, that) for Wellcraft, testing engine and propeller combinations for new boats, or new factory power set-ups for renewed models.
For instance, Wellcraft chose NOT to make a 19' bracketed OB version of the Scarab hull after testing showed that that configuration porpoised continually without putting K-planes down in the water at 10+ degrees at all times - not enough hull length to rocker.
Here's a rule of thumb we came up with, which Wellcraft follows to this day. If you set the hull on the ground, balanced from side to side with the keel line at the transom touching the ground, at 45% of the vessel LOA the hull must be in contact with the ground. In other words, there must be no appreciable hull rocker in the aft 45% of the boat in order to put a bracket on the hull.
The last Wellcraft production hull to violate this rule was the 1990 26' Scarab OB center console. Rigged with a B-bracket for twins, it came factory equipped with either twin Yam 130's, or twin Merc 115's. On plane, the boat porpoised, always. Testing w/ V6 OB engines showed the aft CG made it worse. When we tested the same hull with transom mounted engines, the problem was greatly reduced. The hull had a 37% rocker point.
I have seen many 20 SeaCrafts with bracketed OB's, and all seem to run fine. A 20' Seacraft has a rocker point GREATER than 60%. So does a 23".
On the other hand, my 20' Seafari seems to like it's transom mounted V6 Merc [img]/images/graemlins/cool.gif[/img]

[ocuyler]

Wow! That's experience! What a great site!

[strick]

Thanks for the info Frank. It's nice to have a scientific approach to things. I wonder if anyone has ever done a study and published a paper on the subject of adding a brackets.

Strick

strick

[Capt Chuck]

I would have to disagree with several statements here
A 30" setback of the engine does not change the center of gravity 30 inches The amount of buoyancy in the bracket coupled with the weight of the engine / engines also have to balance, thus the "wave cutting part of the deep vee" hull will not be changed. As a matter of fact, the 410 lbs of floatation in the Potter Bracket Eliminates the typical "Stern-Squat" and decreases the running and the at-rest draft by 3" or 4" [img]/images/graemlins/shocked.gif[/img] The boat will be drier ("NO"Spray rails),Decreased Fuel Consumption and increased Top End and Crusing Speeds with the same HP will be realized. No water into the cockpit when backing down, reduced engine noise and reduction of prop ventilation during tight turns will also be noticed [img]/images/graemlins/smile.gif[/img]

On a 20 footer, the bracket will reduce sliding of the hull. You might experience a slight tendency to porpise at a higher speed but trim tabs will correct that problem real fast. The chance of chine walking with a higher HP motor would be reduced. Added weight by a larger fuel tank and/or moving the twin batteries up forward also must be considered.

All these benefits along with the added cockpit space sold me on bracketing my SeaCraft. You can follow along with my transom transformation on another thread. OK I'm off my