Tayanas have quite thick gelcoat.
Take a pocket microscope and view the surface for 'alligatoring' ... microcracks that look like the back of an alligator. If alligatored then the only course is to re-gelcoat or paint
. Boats with thick gelcoat tend to 'alligator' if left unmaintained/unwaxed in the strong sun.
If not alligatored, wet sand the surface with 1000, then 2000, then 3000 grit wet and dry sandpaper and a sanding
block using a few drops of diswashing detergent in a few gallons of water
as a 'lubricant' and to prevent fouling the sandpaper. The goal is to get down through the oxidation and create a FLAT surface.
Once you have the gelcoat flat and the bulk of the oxidation removed ......
Use a high speed (variable speed) auto body shop polisher (not a cheapo 'orbital' buffer). Buy several real LAMBSWOOL bonnets - never mix grits with the bonnets OR use 3M perfect-it foam pads.
Working in 2ft. by 2ft. 'squares' use 3m super duty rubbing compound #05954. Buff it off with the polisher using a 3m perfect-it foam pad #05723.
Keep the polisher 'moving' so that you dont 'burn through' the gel, avoid corners and sharp edges. Do the whole boat.
Then (2ft. squares) apply 3m finesse-it II #05928 $24.QT. do whole boat.
Then polish it off using 3m perfect-it #05725
Then wax with Collinite's #845 insulator wax or Collenite fleet wax. The last step is THE most important as it will 'seal' the porosity of the gelcoat from further oxidation. If you cant find the 3M products then use 1000 grit, 1500 grit, then 2000/3000 grit auto body compound .... you dont need much, so dont make the bonnet 'soggy' with compound.
Every two years, use an amonia based (strong) detergent or TSP to strip out the old dead wax (old dead wax promotes oxidation) and reseal/buff. Re-wax evey year (or when the water
no longer forms 'tight drops' of water) with a powerbuffer .... take the wax in your very clean BARE hand, add a few drops of water and rub the wax INTO the gelcoat until it begins to shine, then powerbuff. It makes NO sense to apply wax then smear it off with a buffer, the wax has to be pushed INTO the porous gelcoat.
This is the method used when a NEW boat is pulled from its mold
. If done right with diligence you will restore the hull
to better than NEW appearance.
Its a LOT of work but will result in 'brilliant' surfaces. You might want to arrange a 'counterbalance' system so that the weight of the powerbuffer is 'hung' ... and your shoulders wont be so sore when you are done.
OR hire a 'detailing' crew, give them the above directions to follow .... and avoid shoulder 'bursitis'.
Forget the 'orbiting' type of buffer/polisher .... they are totally worthless, get an honest to goodness variable high speed auto body shop buffer (a good one will coat $150-300) and LAMBSWOOL bonnets.
hope this helps.