Cooling system
 

I'm putting circulating pumps back on my engines and want to use the low style stainless steel t-stat housings 18-1989 from Diamond Performance. I'm not sure if I need to install the bypass hose from the top of the water pump to the front of the intake. I looked at the Merc parts listings for 500hp's and 540 bulldogs and some others and it seems some use that bypass hose and some don't. Does anyone know if its necessary and are these the best style t-stat housing to use or are the stock ones from merc better? I'm currently running Gil exhaust. Any help would be appreciated.

Why are you putting the circulating pumps back on the motors?
Is it running too hot or too cold or something?
I was going over to the cross over type system, but have been holding off, because of the stories I'm hearing about running too cold or too hot ?
I do see the bypass hose on many applications, going from the bottom of the intake to the top of the water pump. I'm not sure of precisley what it does?
Good luck and post what you do?
Thanks Brian

The engines weren't building enough heat in them, I was seeing a lot of condensation in the engines. I even tried the cross over with the bypass and the t-stat, but didn't really like the way it worked either. The temperature of the lake water in Chicago really never gets that high.