etrailer.com sells a Taskmaster Load D that I put on a year ago. 2200# per and 8ply. 232 perfect scored replies and I'm just one of them. I've had 2 people come up to me and say it the most impressive looking tire they have seen on a boat. Read the reviews as multiple Phoenix owners like them.
I should note that I have only had my tires for about 1 year. I've never had a marathon blow that was not 4 years old or more. No matter what you get, replace every 3 years no matter. Guys who trailer things 10x more then me all hold this same rule true.