whats the differance in stock merc riser gaskets between the restrictor and non restrictor types. i know the visual diff between them but how do i determine which one i need. they look interchangable so i guess my quesation is why would i chose one over the other. when i took my risers off i had 3 of one type and one of the other type . i have stock merc 260's with stock exhaust and risers. thanks all

yep, check out the service bulletin. Its goes thru all the permutations of stock exhaust systems.

I agree with the 4 hole. Make sure the milled areas are not corroded for a proper seal. If water leaks into the exhaust here you can destroy the engine.

thanks guys. i wanted to get them on this weekend and wanted to get alittle info first. wonder what actual operating differance there is between the two.