I don't know about the potty cleaner but limeaway is fine to use on the cowling.  Like stated earlier I have been using it for 10 years on my Optimax.

 

Another option is a Polymer  Sealer for the gel coat.

One of the best made is a product called Pro - Tec.

A Polymer sealer forms a chemical bond with the Gel Coat to seal the pores preventing contaminants from settling in the pores.

Pros = Bonds to Gel Coat , sealing pores. Usually will last up to 6 months.  Not affected by high heat/sun/brackish water.

Holds a high gloss shine.

Cons = hard to find. Boat must be stripped of any wax first before applying, use a solution like Simple Green/water to wash/strip the wax.

Two coats needed, must wait 12 hours between the 2 coats.

Once the Gel is sun damaged , then it will need to be protected regularly.  One of the easiest ways is to  keep a good wax or Sealer on, and then , after each time out, give the boat a quick wipe down with one of the quick  spray type waxes that contain a UV inhibitor.  This will not only remove the scum line and dirt from the gel, but also enhance the wax/sealer with a thin coat  of UV protection.

Bass Boat saver is an excellent product for this, contains UV inhibitors and wax.

A 5 minute wipe down at the ramp with it or any similar product will help keep your Wax/Sealant working like it should.

Another feature from using this type of wipe down product is that after  the first few times, you'll notice that the scum lines and water spots will become less noticeable and much easier to wipe off.

Basscat7

http://www.protecproducts.com/products.html

http://www.bassboatsaver.com/

Collinite makes one of the best Carnauba marine waxes, The Heavy Duty paste Fleetwax.  Here is a link for them :

http://www.waxbytes.com/marine.html

 

 

Which Pro-Tec product are you talking about for the Gel Coat?  I have a trailer finder that looking dull.