Oringinal manifolds were two hose style. These stainless marine are one hose style, any info on the hose hook up? Its on a 454 mercruiser.

The SM manifolds have more than one port usually the top one is plugged off but you can feed it to by removing the plug and putting in a 90 degree fitting. My engines had the same thing so I fed both bottom and top of the manifolds.

Could T connections be installed at the riser inlet??

Yes, but you need to make sure those are the ones that flow after the thermostat opens, the lower ones have to be fed all the time, which should be the lower 2 hoses coming off the thermostat housing.

These are for just that purpose

http://www.cpperformance.com/p-12828...e-fitting.aspx

The options are to:

Use the Y's that Mild Thunder posted.
Install a T fitting in the hose between the exhaust manifold and the riser.
Get a new Stainless T Stat housing with only 2 outlet hoses like this http://www.diamondperformanceparts.c...8&cat=0&page=2

I used Y's on mine account I got them given to me, had I not I'd have prolly gone with the 2 hose t-stat housing, as Griff mentioned all will work, pick your poison.

Thanks!! Right now im feeding both the bottom & top of the manifolds, may switch to another option later. Did you have any heat issues when plumbed this way??

No, I have run the same manifolds with both a 2 hose thermostat housing (502 MPI) and a 4 hose thermostat housing (HP500) and the temps on everything have been great. You may want to measure your water pressure though when running as it can run a little high at higher speeds.

Two hoses works fine not hard to do !!!