I tired getting this figured out earlier but still have questions.

Thermostat bypass. It looks like water will still flow to the water pump to prevent cavitation. So can I eliminate the bypass line from the thermostat housing to the water pump? Merc keeps this place for either open or closed cooling but it may be more for convenience in building vs real need.

Pics



Incoming from below thermostat. This goes into the flow toward the circulation pump.


Necessary? It would appear the same function is handled by the set up below.


Showing connection from below thermostat to connection on heat exchanger.

I need to make some final decisions on this. I’d really like to close off the second bypass. My brain says it will work but I still question why Merc did it this way. I really wish none of it was needed
really.

Sorry to beat this to death but I think I figured it out. I did a lot of picture searching on the site and found some really good pics of an install done by VinnyP from back in the day. I'll hook up the bypass at the thermostat to the heat exchanger, and plug the circulation pump bypass. A temp sender will go in the thermostat housing with the alarm sender installed in one of the ports on the manifold.

I'm almost done with these things!

I run the bypass hose on mine Tom, and I have perfect water temperature behavior......

Well, now I'm confused. I know I have that hose going up but Now that I'm thinking about it I think it goes into another Barb fitting on the intake manifold.....

a question for seafordguy......how much hp can your closed cooling handle?......been looking for a full CC system for my 572's roughly NA 650 hp a piece.....sorry for the hy jack.

Mine are 800 hp 565's. Temp never moves off 150 even after a 25-30 minute run (although I drive like a wuss). CC was the single greatest thing I have ever done - the peace of mind was worth every penny..... Mine is the CP performance kit and it DOES fit tall decks

Eric, Merc appeared to double-down on the bypass routing. I'm thinking it had more to do with design flexibility than need because the connection from the manifold to the circulation pump does the same thing as the connection going from Merc's special bypass thermostat housing to the inlet of the circulation pump. The bypass on yours is done at the intake manifold/circulation pump connection I'd think.

Hey Tom, I installed FWC on my 454 also. Mine is the Monitor system, but I think they're basically the same. The install manual sucked. I shot them a question about the factory bypass hose and they never got back to me. Nice system, but **** customer service it looks like. The instructions seemed to say to eliminate the factory bypass hose so I did. My motor is running hot right now, but I don't think it's because of that. Possible though. I'm going to use the IR temp gun later today to see if it's really running hot or if it's the gauge. It's running awesome otherwise.

Thanks Dave. I eliminated the bypass on mine. In fact, I might even plug the nipple on the heat exchanger and use thermostats with a couple 3/16 holes drilled to allow coolant to pass during warmup. I haven’t quite made up my mind on that, but that’s the way I’m leaning.

Are you cooling the block only or block and manifolds? And what’s considering running hot? I’m going to target 150 (140 stat) but it will end up being where it ends up being. My MPIs ran 175 even when it was 100 degrees out (but raw water cooled). I don’t mind some heat but I’m starting out conservatively because of them being 454/502 coolers in a 600 hp application.

Plugging the heat exchanger nipple might work better for me too. It was a ridiculously tight squeeze to get the hose on that one for me the way they designed it. The nipples were too close to one another.
Mine is the full cooling system. Block and manifolds. I don't mind a little heat either, but it was holding just short of 210 degrees. Something isn't right. I'm going to use the laser thermometer today and see if I can find it that way. Everything is a pretty tight fit so it's tough seeing what's what.