I’ve noticed some mercury 500 efi’s running only two water hoses to the exhaust instead of four. I’m looking for a thermostat housing to accommodate this style of system. My boat has stainless marine exhaust where the water ports are looped from the header to the risers. So any input would be great so I can figure out which t-stat housing I would need. Thanks

Anyone? Thanks

Unable to swear to it but this is what open cooled BBC used before 806235A1

That ^^^^^^ is for a 502 mag mpi not a 500....you may run into clearance issues, you can block off the other outlets if not needed

Many perf exhausts came with, or offered optionally, y’s to put on each side the 2 hoses into one.

Thanks for the information. Does anyone have the part number for the y’s and where I can buy them? Thanks!

See :
https://www.eddiemarine.com/image/da...structions.pdf

Holy bag they are expensive now. Maybe you can find some others ?

I would suggest regular brass barbed Y fittings

why dont you post a pic of what you have and what you're trying to do, I just rebuilt a pair of 500 EFI's and used the GLM thermo housings, had to do a little modification to them, they make a block off plate for the other 2 hose connections

The 502 MPI style of housing creates a lot of water pressure. Block pressures at speed have pegged my 35 PSI gauges. You may need to add water pressure relief valves.