PCM 351W fresh water cooling (FWC)

Wilhelm where does is hose that feeds the T come from?

As far as the distributor, it more a matter of spark protection.

Where the advance mechanism goes through the distributor there's an opening that gas fumes can pass through and get into the distributor if you have a fuel leak.

The fumes meet the spark in the distributor and you have an explosion that is not contained in the distributor because of that open unprotected path.

The marine version has no vacuum advance and the opening is blocked off but there are a couple of vent holes in the body of a DUI HEI marine distributor that have brass screens in them which keep the explosion contained inside the distributor.

The gas fumes can still get in if you have a leak but like mentioned above the screens prevent the internal explosion from getting outside the distributor so it keeps the fumes in the engine compartment from exploding. The distributor may be damaged internally, but you won't be in an exploding boat.

It works on the same principle as an old miners lamp

Here's a link down below to a thread by somebody who "converted" his Chinese distributor.

In his mind it meets USCG requirements   

The typical factory job has 2 layers of screen per vent hole, not 1 like he did. I think there's a reason for that

Lots of people have survived for a long time without USCG approved stuff on their boat, but it just takes that one bad day to change all that.

link

Some later marine certified distrihbutors are well sealed with no openings for fumes to get into the distributor.

By the way, is your engine normal automotive rotation or if it's reverse rotation, did you have some machine work done to adapt a reverse rotation gear to that distributor?

It seems to me that the manifolds and risers are raw water cooled.

Instead of the raw water going in the front of the manifold, it goes in the rear and up through the riser and out the back of the boat.

KENO wrote: As far as the distributor, it more a matter of spark protection. Where the advance mechanism goes through the distributor there's an opening that gas fumes can pass through and get into the distributor if you have a fuel leak. The fumes meet the spark in the distributor and you have an explosion that is not contained in the distributor because of that open unprotected path. The marine version has no vacuum advance and the opening is blocked off but there are a couple of vent holes in the body of a DUI HEI marine distributor that have brass screens in them which keep the explosion contained inside the distributor. The gas fumes can still get in if you have a leak but like mentioned above the screens prevent the internal explosion from getting outside the distributor so it keeps the fumes in the engine compartment from exploding. The distributor may be damaged internally, but you won't be in an exploding boat. It works on the same principle as an old miners lamp Here's a link down below to a thread by somebody who "converted" his Chinese distributor. In his mind it meets USCG requirements    The typical factory job has 2 layers of screen per vent hole, not 1 like he did. I think there's a reason for that Lots of people have survived for a long time without USCG approved stuff on their boat, but it just takes that one bad day to change all that. link Some later marine certified distrihbutors are well sealed with no openings for fumes to get into the distributor. By the way, is your engine normal automotive rotation or if it's reverse rotation, did you have some machine work done to adapt a reverse rotation gear to that distributor?

Reverse rotation. I can't recall if the PO installed the distributor or if it was done by the guys who rebuilt the motor for me. I suspect there was some machine work involved, yes.

Wilhelm Hertzog wrote:

I’d like to see how the cooling passages line up on those risers. Never seen that style before, though they are handsome. Manifolds look like normal PCM.

Gasket for reference:
https://www.skidim.com/images/RM0002.jpg

I don't see any gazintas

TRBenj wrote: Just 1 connection, rather than in/out? Risers are dry?

Tim the raw water from the hull pickup follows the normal PCM path until it exits out of the Sherwood pump. Instead of running to the thermostat housing it goes to the heat exchanger cooling the block coolant then exits out of exchanger via 1 outlet into that T and then like a raw water cooled engine into each exhaust manifold through the risers and out. They put the water in the back of the manifolds only because the way the exchanger is mounted its outlet is near the bellhousing thus keeping the hose length short. The only real difference here is that he has the exchanger mounted across the rear of the engine rather than PCM's length wise mount behind the Sherwood pump. This is why it is called a half system in the sence that only the block is protected- the manifolds still being raw water. I'm not sure but I think a full system has the manifolds cooled by the block water with block off plates at the manifold to riser joint but the risers are still cooled by the exit of the raw water

I think the vacuum advance is inhibiting water flow

What happens if you remove the statat? that could tell you if you have a enough heat transfer available in the system, and suggest which water circuit the problem is.

Oh - never mind. According to the Shamrock guys these parts can be mounted just about anywhere but they are not to concerned at how anything looks,just that it does the job.

JoeinNY wrote:     I would love to see how they got a chevy manifold to fit a ford.

I figure if you start with a marine manifold for a 5.3 or 6.0 Chevy, a sandwich type adapter plate that would probably have to be "home grown" would make this halfway easy

Here'a a picture of a 6.0 Chevy exhaust gasket and a 351w exhaust gasket, you'll have to visualize the adapter plate.

I think a machinist in South Africa or anywhere else could whip up a couple of those adapters fairly easily

#1 Why not keep it simple till you get things figured out and disconnect the heater or at least isolate it?

#2 The transmission cooler is usually the first place the cool water goes. Some setups have the cooler before the raw water pump and others have it after the raw water pump but in either case, the first thing to get cooled is the transmission fluid.

In the link is a "typical closed water cooling half system" like yours. It's for an inboard outboard and shows the raw water going through a power steering cooler after the transmission cooler, but you'll see the typical flow path.

link

Should I replace the plastic tees and elbows in the system with brass while I'm at it? Or is plastic fine?

outerbanked wrote: 4. Your path should be water inlet, strainer, trans cooler, raw water pump, heat exchanger, tee, exhaust manifolds.

I have a dripless shaft seal. Where in this path should the water feed to the shaft seal ideally be located?

And is it okay to run the engine in gear on a flushing connection with a dripless seal (bearing is lubricated with the water feed?) or will that destroy the cutlass bearing?

Okay, so a follow up after doing the following over the past few months:

No, I didn't. It is the OEM heat exchanger from PCM, and as best I can tell nothing in my engine should make it need a larger heat exchanger. So I figured I'll revisit that as a last resort if I've exhausted all other troubleshooting options.

At the moment I'm leaning towards replacing the impeller to see if that makes a difference. The impeller looks fine when inspected through the pump outlet, but I'm not sure how old it is (which probably means it's quite old), and maybe it's bucket test performance is not quite as good as it should be, which just may be enough to tip the engine into overheating and not maintaining a stable temperature?

If replacing the impeller doesn't help, then maybe there's an issue with my circulation pump not circulating water through the engine well enough?