The one I pulled out had two holes, the new one had none...I get it, with the two holes the manifolds will get some water...but won't letting it bypass keep it running cooler? I'm trying to get it to heat up...

The one I pulled out had two holes, the new one had none...I get it, with the two holes the manifolds will get some water...but won't letting it bypass keep it running cooler? I'm trying to get it to heat up...

this motor ever apart?

yes, it's just been rebuilt, only has 8 hours on it...it runs at 120F on the hose, but cools right down in the water...

I have other issues with it, if you look at some of my other posts...I'm just trying to get through things one at a time...

My 1993 454 mag ran a 6 hose T stat housing original from Merc. Like I said earlier, either Tstat housing should work fine if plumbed and assembled correctly

Mine was the same as what you have. Merc diagram THERMOSTAT HOUSING(STANDARD COOLING) S/N: 0F3519999 & BELOW (mercruiserparts.com)
https://cimg3.ibsrv.net/gimg/www.off...5e8d4a2adf.jpg

I've lined up everything as per the parts drawings I can find. I did check the gauge but not the sender, I have a new one i'll change it next, I'm going to change out the tstat and put the one with the 2 holes in it back in, just to get some flow to the exhaust manifolds....