Raw Water Cooled Atomic4, not flushing water out wet exhaust.

[buzzune]

Hey guys,
My friend and I own an 1978 E34 and have been restoring various elements of the engine to get it running in optimally. As part of this work, I have replaced the water pump, impeller within, all hoses from seacock to exhaust manifold, Petro added a sea screen, replaced thermostat and rebuilt the carb. The engine runs quite well now!

We recently took her out and noticed that she stopped spitting water with the exhaust and the temp shot to 250. We turned around and headed back the 200 yards we'd traveled. We do not have a heat exchanger and only the raw water cooling, thru sea screen and water pump. We notice now that the sea screen is being back-filled with water from the engine as it's hot as shit and dark grey or black.

Primary issue to resolve:
Raw water being pumped in but not exiting the wet exhaust port.

Things I've done to troubleshoot:

1. I have tested the flow of raw water from seacock, thru sea screen and into the water pump. Looks good.
2. Manually turned over engine with water pump cover off and impeller is rotating freely and looks good.
3. I pulled the output hose from the block side to test water flow through pump. Looks good, like a garden hose flow.
4. Have also now removed all the hoses from pump to "tee", to thermostat and over to manifold. All hoses are new and clear of any debris.
5. Removed and cleaned the connector elbow from the exhaust manifold that goes to muffler. That had a ton of carbon build-up so cleaned that and reinstalled.
6. Removed newly installed thermostat for inspection and cleaning, reinstalled. (Of note, this looks like a cheaper chrome version of the brass one I removed last summer).
7. Removed the hose from the block that runs to the muffler to see if water is exiting the engine block. Failed, no water exiting this hose so, I know the problem is in the block and/or water cooled system somewhere.

Questions I am trying to answer:

1. Since all the hoses appear to be clear, could the thermostat be faulty and not opening up to allow water flow through to exhaust? (This seems like one of the places in the system where blockage could occur.)
2. If I need to dig further, would it help to take the engine manifold off to inspect for corrosion inside the block? (I am not certain whether I should check here since raw water cooling seems to route to specific places in the block.

Here is a post Petro added a few weeks ago while we were still sorting out root cause:

Atomic 4 overheating

Hey y'all, Ok, so I have a 1978 E34 moored in salt water. We've replaced the carb, oil filter, water separator, impeller, hoses, and much much more. We have it all dialed in when idling at the dock. Spits water normally and hums right along. We took her out of the slip recently and I noticed...

ericsonyachts.org

I know this is a lengthy post though, trying to provide all my steps to isolate the problem and make it easy for people to offer advice and experience.

Thanks!

Buzz

 

[Afrakes]

Have you visited the Moyer A-4 website and forum? They may have additional insight. I remember a side plate on the A-4. Removal of that would expose more water passages. I believe.

 

[shard7]

Agreed, Moyer is the authority on all things A4.

The symptoms sound like a blocked water passage or fitting inside the engine. Moyer's site has a useful overview of the cooling system, and no flow typically means a blockage (the system always flows regardless of thermostat temp to ensure there's water to cool the exhaust). If the old water pump impeller had missing chunks of rubber, those may now be caught inside the block and impeding flow. The other cause for blockage is just a build up of deposits and gunk from the raw water contacting hot cylinder walls (which may require flushing to remove).

 

[tenders]

The A4 thermostat is a peculiar design and unless you’ve replaced it with one that behaves the way it should, it is surely part of the problem.

This has been discussed at length in the Moyer forums.

I would suggest removing the thermostat altogether, blocking off the bypass hose between the water pump and the thermostat inlet (thus forcing all water through the block), flushing the system with acid to clear out the deposits you’re seeing, and determining how to proceed from there.

i don’t run my A4 with a thermostat at all - the bypass is permanently blocked. The engine runs cool but the flow is very simple. It’s been this way since 1993.