I'm redoing my '87 Merc 260 setup. The stock 4 port setup seems to have a bypass to get water to the exhaust manifolds. The stainless one Sierra 18-1989 looks like it won't give any water to the manifolds until the thermostat opens. Not sure I like that with my Stainless Marine manifolds, or any for that matter.
What's everyone's set up like that has the stainless? Did a search and couldn't find anything on it.

Thanks.

I did another search with different description, I found the plastic piece that comes with the housing is the bypass? It has two, which one?
Should I leave the stat out and put a restrictor in there?

52 views and no one has any experience with this? I believe I have it figured out but I hope it's enough water to the manifolds. = )

i have the iron version of that t-housing. no temp problems. that is the main merc housing for everything from 4.3.to 502 these days.

Yes, it has a bypass.

This one and install exactly how it shows you. The tstat goes on top of the plastic spacer and note the orientaion of the open area of spacer.
http://www.mercruiserparts.com/Show_...PHA+ENGINES%29

Thanks guys, that's what I figured and SB that diagram is a big help. It just helps to hear it even though you think you have it figured out!