My H28

On thing that you might do is to pound on some of those loose looking planks with the heel of your hand or a rubber mallet to see if they rattle. Most of the open seams in the deadwood should close up well. But any planking that rattles a bit and seems to be loose will need a new fastening set to draw them in. Care must be done if this is necessary. I prefer to dip the threads of screws in melted bee's wax and drive them with a Yankee Screwdriver. The Yankee will telegraph the feel of the screw in the wood to your hands and lessen the chence of splitting a frame or plank! Herreshoff called for #14 screws but most builders have used #12s on the H28. It also looks like a bit of caulking might be needed. The dead wood will surprise you by the amount it will swell! Those gaping seams will probably swell shut enough to just squeeze out the seam compound no caulking needed there. It is a matter of lightly tapping in a caulking iron and checking for resistance and bounce of the existing cotton. If it is solid, paint the seams with red lead from Kirby's and pay the seams with oil based underwater seam compound from Kirby's or Interlux. That cotton at the bottom edge of the transom could be driven in a bit but be careful not to crack the transom plank by over driving! Here a fat screw driver bit for a hand brace can do that delicate job. That wide seam at the horn timber at the tuck looks like it might need some caulking driven into it. It will tell you what it wants when you address it! Trust your instinct! You may just want to just selectively caulk where the cotton is loose, prime and pay the seams and put her in for a good soak, while hanging in the sling, with a pair of electric bilge pumps going full bore. If it doesn't take up in three or four days you may need to pull her out and do more caulking. Check the seams inside to see where the caulking is not doing its job. I have been using the same black misquete Drew mallet for fifty years. While it is possible to caulk using a steel hammer, a true caulking mallet makes a difference. If you like, I will loan you my mallet and caulking iron set for the job. If you think you need your own, there are people making good mallets again now. They can be found on line.
The ships store at the Wooden Boat Foundation in Port Townsend had mallets made by Dave Fleming the last time I checked.

Wishing you good luck with your floating work of art!
Jay

Jay should I go ahead and pull out the old cotton and replace it some of it has been removed already. I've checked it for loose planks by pounding on it with my hand and haven't found any yet.

Should I remove the prop, shaft and support so that i can sand prime and paint under it.

If the cotton is truly loose it should be replaced. The strut should be well mounted so no need to remove it unless it is loose. Dolfinite should be used to re-bed it. If you will be sailing in salt water you might want to get some bottom paint in the shaft alley. Other wise, don't worry just squirt some bottom paint in the area using a turkey baster and or acid flux brush. Do check the condition of the strut bearing. Wiggle the shaft by grabbing the prop. If it is loose, replace it and clean the area of contact on the shaft. If the rudder gudgeons are loose on their hull mountings pull them and bed under with Dolfinite and drive a tapered cedar dowel set in G/flex epoxy in the holes. Cut them flush and using a taper drill, of the correct size,drill new screw holes and use new screws dipped in bee's wax.
Jay

Thanks Jay

And when you replace that shaft zince keep it at least the length of the zinc away from the strut. As is, it is restricting water flow to the bearing.
Just my two cents...