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Old 18-01-2021, 08:23   #1
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Old Atomic 4 with no rubber impeller

I've done a search on this website (using Google custom search) as well as a general search of the wider web, and I can't find anything.
Basically I have a 1960s (boat is 1959) era Atomic 4, and my water pump does not have a rubber impeller. Instead it has two bronze (it maybe brass?) gears that intermesh. The lower gear is driven by the engine, and the upper gear is on a shaft, driven by the lower gear, but doesn't drive anything else. The upper gear and shaft are easily removable. Three shafts don't have bearings. The gears look to be in good shape, as do the shafts.
There's a 5/8" rubber hose for the raw water feed, and what looks to be a 3/8" copper tube with a compression fitting for the outlet.
There is a grease cap on the water pump.
The cover plate is held on by eight Flathead machine screws that look to be about 4 mm, although from the age of the engine I'm assuming they're an SAE size, maybe 3/16"
I had the pump off this weekend and used a drill and a bucket of water to verify it does pump water. It's a good strong flow, and of course my drill is running at around half the RPMs that the engine does at idle.
My engine runs consistently at 160f, which I understand that's the thermostat setting for raw water cooled Atomic 4's, so everything is apparently working properly.
I don't have any flowing water from the exhaust when running the engine, but it did make a lot of steam.

Basically I'm looking for any information anybody has on this style water pump for an older Atomic 4 engine.
I couldn't find any manufacturer or model information on the pump. I understand the older engines used an Oberdofer pump with a grease cap, but all the information I can find on those points to a rubber impeller.

Thanks for any information you can share.

Ps I forgot to take pictures while I had the pump off, but I could take it back off and take pictures if needed.
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Old 18-01-2021, 09:00   #2
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Re: Old Atomic 4 with no rubber impeller

Check your exhaust system. Usually on an A4, it had a dry iron riser off the exhaust manifold to the exhaust mixing elbow (where it injected the engine water). Would check the elbow first to see if it clogged/needs replacement. Should be able to pull the hose (from the elbow) and run the motor for a few moments to see if you have flow. If the elbow injector is clogged (and not rusted), would try to remove the clog. If you are in salt water, it probably from calcium carbonate dropping out due to the higher exhaust temps. Should be able to soak it in vinegar or a weak muriatic acid soln. to dissolve the cal carb deposits.
Nice thing about the A4, they had standard US pipe size for the dry riser which one could get at the hardware store. The outside should be wrapped to the elbow to reduce heat and safety reasons.


Edit: I see you are in Indiana so it may be rust clogging the mixing elbow.
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Old 31-01-2021, 17:35   #3
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Re: Old Atomic 4 with no rubber impeller

If the engine has a salt water history, it could be rusted up or clogged with salt crystals in more than one place. Since your pump is good, something is clogged. The water flow is from your pump, up the starboard side of the engine and should have a T fitting about 1/2 way forward that lets water into the water jacket.( into the side of the block). The pipe or hose goes farther forward to what looks like a thermostat housing on the forward, starboard top side of the cylinder head. On the other side of the thermostat housing a pipe/hose goes across the head to the forward end of the water jacket of the exhaust manifold. Water runs down the exhaust manifold to a fitting at the rear end and then to the secondary side of the exhaust loop..
Trouble shooting can begin at the input to the thermostat. Take the hose off and run the engine for a few seconds and see if you have a good flow at that point. If that is good, take the hose off that goes to the front of the exhaust manifold, again run for a little to see if you have good flow. If that is good, take the hose of that goes to the secondary side of the exhaust loop. Check for flow.

Where your flow stops, work backwards and see if it is a simple plugged hose or collapsed hose. Probably wont be that simple. Remove the thermostat housing and prepare to see a nightmare of rusty gunk, maybe solid rust. That is very common. You cant replace with an automotive thermostat. It just wont work. It is possible to run without a thermostat, but it requires careful adjusting of the flow that goes into the side of the block, so it is not advised.

If you had good flow coming out of the thermostat housing, then the exhaust heat exchanger is the next step. With the hoses at both ends removed, see if you can force water thru it. If not good flow, try running some wire into the fittings on both ends to hopefully knock out enough crust to allow flow. If that doesnt give you free flow, I would try soaking it with muriatic acid. Put some fresh hose on each end and tie them so they can be filled with acid and left to soak overnight. Then flush with a water hose. If you are lucky, it might clear it. If not, remove it and take it to a radiator shop and have it boiled out. Everything you do will be messy and sometimes frustrating but not technically difficult.
I forgot to say to check that you have a free flowing supply to the pump.? Is the raw water filter clean? Is the screen on the thruhull clean? Lots of things to check.
Now I will tell you my best advice, find the "Moyer Marine" web site and join their forum. There is endless advice on A4 overheating and any other issue that these engines have. 90 percent of problems are from poor maintenance . They are really a reliable engine if taken care of. I think that I have been too long winded. I hope it helps. Grant.
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Old 31-01-2021, 18:01   #4
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Re: Old Atomic 4 with no rubber impeller

gjordan - thanks for the reply and advice.
It looks so far like a non-issue. My boat is stored inside but not heated at the moment, and I'm not keen to run the engine for long until it warms up.

What I have done is take the thermostat out and verify it works with a pan of boiling water and a thermometer. It opens somewhere close to 160f, as near as I could tell with a non-digital thermometer.
There was no rust or corrosion anywhere at the thermostat or housing. Externally, there's not much rust anywhere on the engine. The paint is in good shape, and it looks older than the hoses and too neat to have been painted in place with disassembly. photo below
Once it gets a warmer and I move my boat outside for a few weeks before Spring launch, I'll feed water and run the engine and do more investigation.

I've taken every hose loose and there's no blockage, gunk, or rust anywhere. It looks like all the hoses are no more than a few years old - which coincides with the extensive refit the PO told me was completed over several years before he purchased the boat.

I doubt my boat has ever seen salt water. It's possible of course, but I bought it in Michigan last year, where it was kept on Lake Huron, and the only charts from the 20ish year old gps are Lakes Huron, Michigan, and Superior. It was originally built in Ohio, and from everything I can tell it's never been as far from the Great Lakes as I have it now.
I've extensively searched Moyer forums and found nada on a water pump without a rubber impeller. I haven't posted any questions there yet though, so maybe someone will have a hidden nugget of information when I finally do.
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Old 31-01-2021, 18:20   #5
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Re: Old Atomic 4 with no rubber impeller

Bronze gear water pumps were common at the time of your boat's construction.
As posted above:
1. Remove hose from exhaust elbow water inlet. Run engine. Does water flow?
2. If no-remove hose from water pump outlet & run engine.Does water flow?
3. If no-check suction line from seacock>water filter>pump inlet. Look for air leaks,hose collapse,blockage. Can you blow back thru the pump inlet hose & out thru the seacock?.
Cheers/ Len


See "constant flow water pump without motor". This is what the old all gear pumps looked like.
https://www.mcmaster.com/bronze-gear-pumps/
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Old 01-02-2021, 11:45   #6
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Re: Old Atomic 4 with no rubber impeller

If it is as you say, "only steam coming from the exhaust" then you certainly have some type of problem. Even the relatively small amount of water it takes to cool an A4 should show as water(probably as spits and drabs) coming from the exhaust, not just steam. You will have fun in the spring getting it sorted out. They are a good basic engine. Grant.
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Old 01-02-2021, 12:00   #7
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Re: Old Atomic 4 with no rubber impeller

The best place to look for Atomic 4 advice is Moyer Marine. They have a forum the only thing that they talk about is A4's. Any part or information that you need you can find there.
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