Outboard bracket mounting specifics - question

[Captain Koz]

Hello.
I have a 26" setback, 17 degree angle, Stainless Marine brand bracket that is on a donor boat, which I am going to transplant to a 25 ft Aquasport center console (1979 246 CCP). I know that the cavitation plate has to be about 1 inch above the bottom of the boat for every foot of bracket setback, in this case lets call it 2 1/4 inches above the bottom of the boat. I believe I am over thinking this all out, but I want to make sure I am correct as once it is mounted there is no turning back.
As you can see in the pic, I used a floor jack to hold a an angle iron (straight edge) along the bottom of the boat, and used a level to make sure it is level. Then I clamped another angle iron to the bottom of the cavitation plate. I measured the difference to be about 2.5 inches. I measured 24.5 inches from the top edge of the bracket to the cavitation plate and then to the other angle iron and got 27 inches for a difference of 2.5 inches.
Am I on the right track? My confusion is mostly around the fact that tilting the motor will produce different spacing between the cavitation plate line and the bottom of the boat line, so am I correct in taking all these measurements with all parts level? Will this method give me a correct installation? I am planning on cutting a piece of plywood at 26.5 inches (2 inches above the bottom of the boat) and bolting it to the bracket to use as a guide for installation. This way all I have to do is have the plywood meet the angle iron representing the bottom of the boat. Yes, its a half inch shy of my measurements (2 1/4 inches), but that is the lowest that motor will mount on the bracket, so I can always raise the motor to increase the distance. Will this work?

 

[Bob_VT]

Re: Outboard bracket mounting specifics - question

That will require a FULL rebuild with new strings, bracing and a tremendous amount of work. Honestly I do not think it would be worth it to install on a 1979 hull. The stress is multiplied due to the length of the bracket. It is a big lever with over 300 lbs of dead weight and that is not counting the stress under power.

If your pockets are deep enough to install the bracket properly.......????

I would not attempt it.

 

[metriccrescentwrench]

Re: Outboard bracket mounting specifics - question

I know that the cavitation plate has to be about 1 inch above the bottom of the boat for every foot of bracket setback, in this case lets call it 2 1/4 inches above the bottom of the boat.

That figure is just a starting point, not the be-all-end-all for setting engine height. The actual optimum engine height will vary based on individual hull design. Personally I doubt that there's a lot to be gained by getting so radical with setback. I'd also think that it would be extremely useful to have a hydraulic jackplate with something like that. You might want to check in at screamandfly.com and ask some questions, there are plenty of guys there with tons of high performance boat setup experience.

 

[MH Hawker]

Re: Outboard bracket mounting specifics - question

I am wondering why you would ever need some thing like that in the first place. a jack plate I can understand.

 

[briangcc]

Re: Outboard bracket mounting specifics - question

To me, and I'm just a schmuck, that looks like a bracket to convert an I/O to an Outboard. But I've been wrong before...

 

[dingbat]

Re: Outboard bracket mounting specifics - question

I am wondering why you would ever need some thing like that in the first place. a jack plate I can understand.

Brackets are very common on offshore, outboard powered boats. The brackets adds buoyancy, increasing fuel efficiency while making the boat ride 2 feet bigger. They also allow mounting outboards w/o a cutout in the transom.

I see no advantage whatsoever of a jackplate on an offshore boat? How would one benefit from a jackplate in an environment where the prop is out of the water on one side of a wave and the power head is getting wet on the other?


Your on right track. Here is some additional information
http://dadmarine.com/25sgl.html

 

[Captain Koz]

Re: Outboard bracket mounting specifics - question

Thank you everyone for your suggestions. Bob vt, I am doing the work myself which will cut costs down significantly. Yes, the floor is coming up and I will build knees from the stringers to the transom. Yes, it's an older boat but they were over built back then. It's an amazingly good hull and I love the boat. I had the 20 ft version for a few years and its a great boat. There is a site, classic aquasport.com which outlines many a rebuild so I k ow it has been done and can be done. The rebuild will cost me about $5,000 in materials. Where can I get a 25 foot offshore center console all redone for $5,000? Is an awesome boat and it will be a great experience and feather in my cap to do it the way I have planned.

Thanks dingbat, I have seen that site but their measurements are for their bracket, but a fair amount of that info is applicable. I appreciate it.
To be clear, I'm not looking to make it a rocket ship. I don't care how fast it goes. I just want the motor properly installed more from an efficiency perspective. Also, the higher the better as a bracket makes the motor more vulnerable to trailing waves.
Briangcc, yes, they are used for I/o conversions however I am using it to create a bait station along the transom. My boat has a cutout for twin outboards, so the stern is almost all wide open and a lot of wasted space. The bracket also smoothes out the ride a bit making it act like a longer boat.
Thanks metric, I will post a similar question on that site as well.