I was going to look into that myself, because it is a better design esp for raw water cooled manifolds/risers. But I was not sure that the angle of the Merc risers could adapt to the OMC/Volvo style Y pipe. So I went with the standard Volvo design knowing that it would fit for sure. However, the next time if I still have this boat then, if I can get a shop to loan me a mani & riser I'd like to see if it could be made to work. They are more expensive than the standard style ones, but probably worth it. In Tony's case of a boat with full closed cooling, there may be some advantage to the standard risers because the gasket used for full closed cooling on the dry joint system is even less likely to fail, than the one used on the wet exhaust. Whatever you use, the key is to use good gaskets and in salt those risers have to be taken off and probably replaced at 5 years, if not the manifolds too.
