Can't clean the rubber strip around stern, try using dinghy inflatable cleaner with a Scotchpad, it comes up like magic.
If it's been a long time neglected you will need some elbow grease.
I am on a maintenance week lifted out so a few tip are being posted.
Hope this helps
Odysseus
I've always used Acetone, but I don't like it. Which particular cleaner did you use?
Any inflatable cleaner but I happen to have starbright (I think) fender cleaner or the like.
Odysseus
I use a liquid cutting polish, this is much cheaper than Starbrite, and it doesn't take much elbow grease to get results either. Brings it up sparkly new. Can be used sparingly on the GRP for stubborn stains (eg rust stain from gas bottle) too.
I'm going to try some 303 Aerospace Protectant (http://www.amazon.co.uk/exec/obidos/ASIN/B0004ELKC4/dolcetto-21) next time, I've heard good things about it.
Interestingly to see how you get on with that, let us know.
I use a nano polish on my hull and the rubbing strip, its called devil shine, in most auto shops and even Asda.
Put Nano polish into google.
It was developed for the shuttle, and known a A Glaze in the auto industry.
Hope this helps
Odysseus
Try cif kitchen cleaner, works great and doesn't effect the rubber. ;)
I use vim it costs £1 just mix into a paste and use a nylon kitchen scourer