Oh boy here I go again, I've been piecing together this motor for a year now, and every time I make progress and buy a bunch of parts, they end up being WRONG, I damn near can open my own marine store of all the parts that are wrong. But anyway, I bought an original housing with the "T" ball bypass not knowing when you install EMI's you would have to install a "Y" pipe to both hoses. Well I don't want to do that!! I see a lot of guys running a stainless housings like in the picture. My question is this, if the thermostat is closed how do the manifolds get water? Does it have some magic bypass that I can't see inside it? and what the heck do them colored plastic pieces do? One more important thing, will it fit on an intake that the mounting holes are 80 deg off centerline. I already made that mistake the first one I bought, what you see on the motor is number 2. Oh and I don't want to do crossover either, my pump is new also. Thanks any help would be GREAT!

I have a Merc of the first style and added a hole for my pressure bypass. I would use the second one and take the T out and put a brass pressure relief in it and dump it overboard. The small slit in the riser dump didn't let enough water out and my pressure got pretty high. BTW, yes I have EMI exhaust as well.

Captain Jack, You got a whole lotta hosin goin on there,LOL The polished housing in your 1st pic is similar to a stock housing that had the check balls on springs. If you look at the underside it has a floor that the thermostat fits in & the plastic piece holds the thermostat. The openings in the plastic piece is the bypass. The brass fitting is for a sending unit. The slotted mounting holes allow it to mount off center. Being you already painted & mounted the housing in pics 2 & 3 I agree with ACrook take the brass "t" out & put a pressure dump valve there, makes it easy to get to for adjustment,etc. Looks like you will need to plug the bypass on the circ pump if you don't have a fitting in the intake for it. You will need 4 barb fittings 2 for the manifold & 2 for the risers & run a U hose to connect them. I f you run the polished set up it would look cleaner & function the same way you would have to put a pressure dump elsewhere if you plan on running one. Good luck with your very nice looking engine. Randy

The SS Tstat housing you posted has an internal bypass.
The other option is to use a T fitting with the current Tstat housing like Merc used on engines with Gil exhaust.
Either way will work fine.

Well thanks for all the advice guys, I guess I'm going to try the cheap way first, I just ordered a bunch of fittings to make the GIL look-a-like fittings 3/4 NPT street tee, with 3/4" hose barbs for the risers and 1" hose barbs with 3/4 NPT for the by pass hoses. If this doesn't work I'll just break some more off in my @#@# and try the other route. Who would have thought I would end up spending $10,300.00 on a single engine one damn piece at a time. Makes me sick every time I see nice engines for sale in swap shop for WAY less. All I know is this biitch better run like a scalded dog!! This is really a hard lesson learned.
Thanks everyone

Update, I got all the fittings in and didn't like all the clutter, so ended up ordering the stainless thermostat housing (its a nice piece) and its got bing!