Flow of raw water through motor

Been rebuilding and restoring my GT40 and trying to figure out the flow of water through the motor before it goes back into boat. Im sure this is wrong but I will start with this flow pattern and you guys correct me. Water comes into the upper thermostat housing (via raw water pump), upon startup thermostat is closed so water can't pass down into the 1.25" white stripe rubber pcm hose that feeds the engine water pump so until warmed up it gets directed from the upper thermostat housing intake straight to the 2 upper thermostat housing outputs which direct the flow of water to the right and left exhaust manifolds and then is expelled overboard. When engine reaches temp the thermostat opens allowing raw water down into the 1.25" white stripe pcm hose that feeds the engine water pump which then pushes water into the right and left side of the block where it flows up each side and exits out the lower intake plenum into the upper thermostat housing and out to the right and left exhaust manifolds and expelled overboard. Im sure that's wrong because with that flow pattern I don't have any water running to the engine water pump and through the block UNTIL the thermostat opens....enlighten me please...

I'm not familiar with the gt40 particularly. so exact application might differ. But most raw water cooled engines are similar in design.
your forgetting about your circulating pump which is the main center pulley on the front of the engine. Most engines the coolant flows from the block into the heads. unless its a cadillac northstar then it goes all over the place and never gets a chance to normalize. but thats another story.
Anyways i found this picture in a google search

That smaller hole supplies water to the circulating pump on demand. meaning the RWP is supplying the water to the circ pump and anything the circ pump doesn't want will flow through and out the tstat housing. once the engine warms the water thats before the tstat enough to open it the circ pump pretty much takes the majority of that feed and circulates it rather than it going through the bypass.

That makes sense. Behind the engine water there are two water jackets. Looks like one going to left side of block and one to right side. Are this both pump discharge jackets or is one a discharge and one an intake for the engine water pump? So the closed loop (prior to thermostat opening) is circulated between those two jackets behind engine water pump? Or are those both discharge jackets that allows water to the right and left side of block and the closed loop (prior to thermostat opening) is completed in the upper thermostat housing?

Here is a picture with the engine water pump off. The top hole in the lower intake plenum is discharge from engine block and heads? The two right and left holes where the engine circulation water pump goes are both circ pump discharge or is one intake and one discharge? I'm talking about just when the system in is "closed loop" for lack of better term I'm referring to before the thermostat opens. I'm getting it slowly here.... Thanks

I think pretty much that entire statement is incorrect, Pete.

TRBenj wrote: I think pretty much that entire statement is incorrect, Pete.

Tim,
How so?

Like Gary said, the large (1.75") hose feeding the circ pump from the stat housing is the inlet. That passage is always open regardless of thermostat position- like was said above, the block will always fill up with water if it's empty. The 2 ports on the back side of the pump are the outlets (of the pump, ie, inlet to the block). The engine fills/flows from the bottom up (block-->heads-->intake) and the thermostat controls water flow out of the intake. Even when the block is filling, there will be some amount of water cooling the exh manifolds.

This is the basic PCM ford set up. Other cooling systems do it a little differently- Chryslers, HM's and interceptors that lacked circ pumps, LT1 indmars (reverse cooled), fresh water cooled engines, etc.

8122pbrainard wrote: TRBenj wrote: I think pretty much that entire statement is incorrect, Pete. Tim, How so?

So what's incorrect with pretty much of my entire statement??

Tim, just so I don't confuse you any more with my wording, I found a very nice PICTURE on how it works.
Note the picture does show water exiting via the risers and not the manifolds and then out the risers.

FWIW -- This is the way the water flows through MacSkier:

    MacSkier cooling

You will have to follow the links to see how this was determined. I'm now quite confident of my understanding of the cooling system on the 1972 Skier. (The thermostat may never open.)

-=Grant=-

My boat’s cooling system uses lake water to cool the engine — a 302 Ford V-8, marinized as a Conquerer-Crusader (when they were owned by Thermo Electron, equipped with its original (1972) exhaust manifolds.

Unlike the closed loop systems systems found in cars and many boats (which use a "radiator" or heat exchanger and thermostat to supply coolant of an appropriate temperature), the cooling system described here uses the practically unlimited amount of lake water to cool the engine.

A "raw water pump" moves a large volume of lake water into the boat, through the power plant and -- mixed with the engine's exhaust, out of the boat.

When the water exits the RWP, it first passes through a small heat exchanger used to cool the transmissions cooler. (This increases the water's temperature a few degrees. We measured it.)

Leaving the transmission cooler, the water enters a two-part chamber containing
1) a pressure relief valve and
2) a thermostat.
The two chambers are adjacent, but not completely separated. There is a passageway between them.

The lake water is pumped into the chamber containing the pressure relief valve. The valve is pushed open, and much of the water flows through it, then out the top of the chamber and on to the front of the exhaust manifold — cooling the manifold.

The water that does not exit the chamber via this route, enters the chamber containing the (now closed, and possibly always closed) thermostat, then out of that chamber to the engine’s circulating pump — a recirculating type pump. The pump pushes this water through the engine block, through its heads and through its intake manifold. The water exits the exhaust manifold (where a car’s thermostat would be located.) The engine’s pump pumps the water into the front of exhaust manifold — and aft, via two “side” passageways in the manifold.

A cross section of the exhaust manifold reveals four passages; one for the exhaust gases, and three for water. The top passage carries the water previously described, i.e., via the pressure relief valve (and via the thermostat if open.) The two other passages, one on each side of the manifold are fed by one inlet at the manifold’s front. At the rear (aft end) of the manifold, there are three possible exits, 1) a side exit to mix with the exhaust gases, 2) another side exit to mix with the exhaust gases, and 3) a bottom exit that carries water back to the thermostat chamber. I refer to this “bottom” flow of water as the “lower loop.”

It is this “lower loop” water that has been heated by the engine block, heads, intake manifold and exhaust manifold. It is circulated by the engine’s pump back to the thermostat chamber where it is mixed with lake water being introduced by the RWP.

If there is enough of this “lower loop” heated water returned to the thermostat housing it will raise the water temperature in the housing enough to open the thermostat, permitting more cool lake water to enter the block, etc. If there not enough of this “lower loop” water to open the ‘stat, the ’stat will stay closed.

We have experimented enough with this system to know that restricting “lower loop” water from exiting the rear of manifold, we can raise operating temperatures to desirable ranges. But we will not be doing that until we can experience higher lake water temperatures.

In summary, if you want good, predictable engine operating temperatures in your inboard boat, get one with a “closed loop” system.

-=Grant=-

He probably just got the M upsidedown, then the C exchanged places when he wasn't looking.

Im so confused.... I'm not even sure who I am anymore?

Exactly Thomas. Much like sausage you don't want to know how it's made. Just remember - never run it dry and keep the clamps tight.

Gary S wrote: Just remember - never run it dry and keep the clamps tight.

Gary, are you talking about his sausage or his cooling system?

C-Bass wrote: Gary S wrote: Just remember - never run it dry and keep the clamps tight. Gary, are you talking about his sausage or his cooling system?

Yes both