adding a prop pocket?

Still a fair bit of extra weight, and a different shaft angle , plus the prop tunnels, will be a different boat. There is always the opportunity to counter any squatting tendency with tabs/interceptors. Looking at what others may have done in a similar vein with the same hull, would be helpful.

 

adding a prop pocket

There are better ways of achieving what you want by looking at other examples such as Hickman`s Surface Piercing set up and he achieved 60 MPH + with all of that heavy gear and slow RPM.

Some people say you can not run a prop close to the transom and you need a long shaft to clear transom disturbances. Pretty much horizontal shaft in that image and very simple.
Google Images boat "boat shaft drives " for more inspiration.

 

So maybe a ZF 220A @ 1.235:1??

That gets a Pitch around 22", and looks to make good use of shaft and prop $$s. And with a diameter of 18", still enough extra area that getting on a plane shouldn't be a problem.

I don't have P.E., I ran it through a freeware and some paper charts.

I think this may be a case where abusing one particular person, namely, the best prop guy you know, will get you there without messing with the hull. It looks like just the right 18 x 22 or so will do. They shouldn't cost any more than a stock set of 20" wheels and a size larger shaft.

 

1982 Blackfin Yachts 32 Flybridge


The 1982, 32 Flybridge is a 31.75 foot inboard boat. The weight of the boat is 15460 lbs. which does not include passengers, aftermarket boating accessories, or fuel.

Information on this page is provided to you as a free service of iboats.com. Because this information has come from many sources we can not guarantee its accuracy. Even if this information is the same as the original factory specs, boats are sometimes modified. Thus, for safety and other reasons, it is a good idea to verify information here to make sure it matches up with your boat. For additional information, we recommend the iboats forums and a boating safety course.

Engine Information:
This boat may have come with the following or other engines :
(In the interest of safety, never exceed the manufacturer's maximum horsepower rating for your boat.)
410 hp diesel with 2 engines ( 205 hp diesel per engine)
600 hp diesel with 2 engines ( 300 hp diesel per engine)
700 hp with 2 engines ( 350 hp per engine)

I ran across this on a spec website and differs considerably from your 8500 dry weight
A 32 foot boat weighing in at 8500 seems light.Might be worth confirming

 

The 375hp TA was an option as well at some point in time. This on the heavier flybridge boats that cruise in the mid 20's. There's lots of info on Boatdiesel and Blackfin forums about diesel setups.

 

Barry, not the same boat. Mine is the version originally built as a Cary 32' before blackfin bought the molds. Here is what mine looks like and the specs I give are accurate:

 

Phil, started with this route. Issue we found was with the top speed and shaft angle creating excessive cavitation on the prop (analyzing using a Michigan dqx 4 blade). As I mentioned above, though also not a PE, I have experience sizing running gear, including props, and in my business have had dozens upon dozens of experiences getting to analyze data in the design phase then compare it to the real world results when the project was complete.

I have zero experience designing a tunnel, but do have some experience sizing props for existing prop pockets/tunnels (the single screw 24 topaz I have had for the last 16 years has had many different props on it).

Since I can't seem to find results I like without having to modify the hull, I wanted to start looking at what benefits I may could gain with adding prop pockets/tunnels. with a 20" wheel and 10 degree shaft angle (1.533 gear ratio) I start getting some real good numbers from the prop with the cavitation levels I am seeking.

This is why I am now looking to focus on analyzing adding prop pockets/tunnels to the hull. believe me, I am not trying to add tunnels just to do it. I just want to get the best set up I can get and since the hull is an early 70's design, seems plausible to improve on it....