Try Joe at Zippkits these cant be beat for the price but if your just needing a slow boat then you could try a clone.Pretty sure these will be available in the states.
personally if your looking for a slower hull then id go with a big electric motor and a large lead acid battery,a few people have used the mobility scooter motors and the ones from kids ride in jeeps etc for this,they give great power and long run times.
Mart
http://zippkits.com/~zippkits/index....roducts_id=489

http://www.ebay.co.uk/itm/26cc-RC-Bo...item25677d3800