I've used Motoseal for several years on Jetskis and Banshee. But Threebond (1184, superceeds 1104&1194), 1211,1215, Yamabond, Honda Bond, (basically any brand name with the suffix -seal or -bond) all work well with many being Private label Threebond products. Seadoo uses/used Loctite 518 and catalyst to seal case halves. I've heard of people using Aviation gasket #3 also.
RTV is not recommended for this application.
The most popular are the Threebond, Motoseal, and (insert company name)bond products.
edit: looks like possibly Yamabond 4 is Threebond 1184 FWIW