Confirming the finer details of my BBC full cooling system plan.

Looking to see how I can flow coolant through the exh manifolds before the thermostat opens.

BBC & 420 blower @ 650 HP.

Full systems are not as common for sure. PNW sea water is relatively cool, and I would prefer to have less manifold leaking issues.

What options do I have to get water flow though the exh manifolds prior to engine heat up?

Thanks,

Art

Mine always flows through the exhaust, thermostat only controls flow through engine. Thought all Merc set-ups were like this.

Do you think the circulating pumps short cut or what ever it is called, aint enough. Have also tought to convert mine to full, it hurts to fill my new stainless marine manifolds wit salt water.

My plan was to use two of these with block off plate between them and 90° automotive thermostat housing. Thermostat to the block wich is on top, and also the bypass hose for ciculating pump. I quess you have very limited space between the blower and the intake, so this does not work for you. One thing that scares me in full system is temperature difference between the manifold vs riser, dont know if that is a problem.

Liberator, are speaking to raw water through exhaust manif or your circulation coolant?

Jani, great find on the 3 spout thermostat housing manifold. I'm more concerned about ensuring the exhaust manifolds don't overheat vs bypass circ pump.

My SM manifolds shouldn't have thermal issues with the stainless raw water tails. Very little contact at the joint. Manifolds shouldn't get hotter than 160f, unless the heat exchanger can't take the load...!

Water temps where I boat are never more than 70f.

It occurred to me that just setting up the engine coolant outflow to exh manif won't allow sufficient flow unless the thermostat is open.

Creating a scenario where the exh manifolds are overheating.

Potential solutions:
1. Restrictor plate circ coolant flow with a remote thermostat attached to heat exchanger...opens flow to through heat exchanger. This would help engine warm up time. Heating coolant with exh manifolds.

2. Harvest circ pump output before entering block to feed block and exh manifolds. Not keen on this option...messes up the circ pump pulley alignment and blower belts etc.

Sorry my bad english, put my point is that there is a coolant flow thru the engine/manifolds when the thermostat i closed, if the bypas hose is used, from under the thermosta to circulating pump. Also i think the thermostat would start to open fairly quick in full system. just a tought.

I have an open system and now realize you must have closed system with heat exchanger. Sorry for the confusion.

From gathering info and reading threads I've seen that full systems often create confusion. My bad for not explaining better.
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i managed to see a YT vid of a guy installing a full system. The heat exchanger has a remote thermostat. It uses a a single hose as a recirculation (looks like a 3/4").

I would prefer to do that at the intake man location. So maybe a simple thermostat block with a smallish bypass built in.

1/2" bypass. Something like that. Enough to keep the exh manifolds from overheating, and they can contribute to engine warmup.

My 1986 Mercruiser flows this way.