Hi everone I'm in need of risers and manifolds for my 1987 mercrusier v8 260hp. I want to get the manifolds that will last the logest in a raw water cooled engine. Is OEM the best way to go or is afternarket ones just as good. I see a set like GLM and there cheaper and claim to have better water flow but I don't know if it's true. Please send me your opinion and let me know whats the best way to go oem or aftermarket and which brand. thanks for youy knowlege and happy boating.