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'78 E27 Atomic 4 Universal Overheating

chrisoelder

Member II
Got a strange issue (at least strange to me), I bought my boat 2.5 weeks ago and it was running great the first weekend... well after I got new batteries. I took her out last Saturday (cinco de mayo), she warmed up for about 15-20 mins. While warming up I had it in neutral and little to no throttle, the exhaust looked normal and the raw water flow was going not a lot but more than drops. After pulling out of the slip and motoring down the channel I noted some smoke coming from the engine compartment. I removed the cover and turned off the engine. The exhaust raw water flow was very little at this point. After sailing around the marina for about 30-45 mins I restarted the engine. Let her warm up for a few minutes, then threw her into gear to get us out of the channel, raw water flow seemed normal to what I was used to with the boat. While out in the Santa Monica Bay I used the engine for about 15 mins and again she was running fine with normal raw water flow. When coming back into the marina we decided to do a little harbor cruise. We were motor sailing and the engine started to overheat again. The engine was in neutral for the most part during the harbor cruise and the water flow became very little.

After getting back into the slip I concluded it wasn't the oil but most likely the impeller was old and not creating enough suction at the lower RPMs to cool the engine. Sunday (5/6) I took the impeller out and went to West Marine. I had their expert take a look at the impeller and he believes that isn't the issue. The impeller is in good shape, a lot of movement with the arms and not a lot of corrosion. He suggested I take a look at raw water filters, thermostat, the exhaust line, and any possible clogs or blockages. After returning to the boat I looked for a raw water filter but couldn't find one in the line. So I took the housing off the thermostat and there was nothing there, no thermostat, nothing. I took some photos and videos, please use these links to view them.

https://drive.google.com/file/d/1t7cD7JQqnULFe95oEjuY7XBFJtYlQVAR/view?usp=sharing
https://drive.google.com/file/d/1m7aMR56dCC5kK8g1ApFcncM4TDBMyEs3/view?usp=sharing
https://drive.google.com/open?id=1cMVyRr2ds17H3T4Nywg_uXcBwNb52_R_
https://drive.google.com/file/d/1eRPyy529WQfpTFe3Csn9Cx7l_phFKnGy/view?usp=sharing
https://drive.google.com/open?id=1yw6fvKjtVNR-uV3gYaHiJc8x5AfdGQ0n

Is that normal?

I am looking for any and all suggestions to what is causing this issue. Also is there a way I could "flush out" the system to see if there is a blockage somewhere down the line?

Thanks!
Chris
 

Cory B

Sustaining Member
Moyer Marine

Hi Chris,

Its been a few years now since I've had an Atomic 4, but it sure looks like you are missing a thermostat.

There may be other issues as well, but that is a good the place to start. Although I think a missing thermostat would make the engine run cool rather than hot. Maybe you have a blockage somewhere? Or maybe your waterpump has issues and you need a new one?

Anyway, for all things Atomic4 related, check out MoyerMarine.com. It was (and hopefully still is) an amazing resource for both parts and information.

The A4 can be a fine engine as long as they are maintained.

Good luck!
 

Jenkins

Member II
Hi Chris,

When running an A4 with no thermostat, you need to have a valve in the bypass. The bypass is the hose that goes from the fitting on the side plate to the thermostat. The purpose of the valve is to mimic the action of the thermostat.

The cooling water comes from the water pump and goes to the fitting on the side plate. That fitting is a t-fitting that allows cooling water to either go into the block or up to the thermostat housing.

As designed, when the engine is first started and cold, the thermostat is "closed" - which means that it does not allow any cooling water from the block through but it does allow full flow through the bypass tube. This is to ensure that we always have cooling water going through the exhaust manifold and being injected into the exhaust.

As the engine warms up, the thermostat "opens", which allows cooling water from the block to flow and reduces the flow through the bypass. An equilibrium is eventually reached where the engine runs at a stable temperature with some cooling flow through the block and some through the bypass.

When the thermostat is removed, it is necessary to put some restriction in the bypass to ensure that some cooling water indeed flows through the block. The idea is you put a valve in and adjust it until you get to an operating temperature that you desire. You may find that you need to make this adjustment a few times over the course of a season if your raw water temperature varies significantly.

Let me reiterate the suggestion that you get over to the Moyer site - it is THE source for A4 info and parts.

Best,

Peter
 

toddster

Curator of Broken Parts
Blogs Author
Another thing that happens with these old water pumps is that eventually groves get worn into the case and the cover plate so that water just goes around the impeller blades and the pump output gradually decreases. It doesn’t take very much of a groove. Sometimes you can revive an old pump by lapping the cover on a piece of sandpaper to take out the wear marks. Eventually, you just have to bite the bullet and spring for a new pump.
Or so I imagine. Both of my pumps are on their second lives at the moment... :rolleyes:
 

chrisoelder

Member II
Thank you, everyone, for the help! I truly love this forum!!!!

@alcodiesel @Cory B - I am going to head to moyer and post my issue, thank you for the suggestion! It does look like they have a lot of A4 info.

@toddster - I did take a peek into the pump with the impeller out and shaft out. I didn't see much but I really wasn't looking too hard. I will double check if there is any wear from the impeller. If so, I will give her a nice sanding to smooth them out.

@Jenkins - Would replacing the thermometer resolve my issue or is it better to install a valve? I am thinking a thermometer will be easier than fine-tuning a valve every couple of months. To @Cory B's note, would not having a thermometer in there make the boat run cooler? I am trying to determine why someone would remove a thermometer and not replace it at all.

Thank you, everyone, for the help! I will let you know what I learn from moyermarineforum.com

Please feel free to keep posting suggestions and theories :D
 

Jenkins

Member II
Would replacing the thermometer resolve my issue or is it better to install a valve? I am thinking a thermometer will be easier than fine-tuning a valve every couple of months. To @Cory B's note, would not having a thermometer in there make the boat run cooler? I am trying to determine why someone would remove a thermometer and not replace it at all.

Most folks go with the valve because the original thermostat is very expensive ($165) and you need a nice clean thermostat housing for it to operate correctly. Moyer has just developed a replacement for the original that comes in at $125.

I set my valve once and leave it - sailing in a body of water that does not see the temperature vary much.

As a simple test, you could clamp off the bypass and see if that solves the overheating problem.

Does removing the thermostat make the engine run cooler? On most cars this is true. On the A4 this is not true.

The A4 cooling system is set up to make sure that there is always a good flow of water through the exhaust manifold and then injected into the exhaust system itself. When the engine is cool, the thermostat is open on the bypass side and closed on the block side. All cooling water flows through the bypass hose, into the thermostat housing, directly out the other side of the thermostat housing and into the exhaust manifold. As the engine warms up, the thermostat reduces the bypass flow and allows flow to come through the block.

Removing the t-stat creates a very low resistance path through the bypass and most of the cooling water goes that way. Adding the valve in there restricts the bypass flow and ensures there is adequate flow though the block.

People remove the thermostats for various reasons.
1) they break and are expensive to replace
2) engine is overheating and surely if we remove the t-stat we will increase cooling? (this is incorrect thinking on an A4)
3) thermostat housing has become degraded and thermostat is no longer operating correctly.

Peter
 
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chrisoelder

Member II
Most folks go with the valve because the original thermostat is very expensive ($165) and you need a nice clean thermostat housing for it to operate correctly. Moyer has just developed a replacement for the original that comes in at $125.

I set my valve once and leave it - sailing in a body of water that does not see the temperature vary much.

As a simple test, you could clamp off the bypass and see if that solves the overheating problem.

Does removing the thermostat make the engine run cooler? On most cars this is true. On the A4 this is not true.

The A4 cooling system is set up to make sure that there is always a good flow of water through the exhaust manifold and then injected into the exhaust system itself. When the engine is cool, the thermostat is open on the bypass side and closed on the block side. All cooling water flows through the bypass hose, into the thermostat housing, directly out the other side of the thermostat housing and into the exhaust manifold. As the engine warms up, the thermostat reduces the bypass flow and allows flow to come through the block.

Removing the t-stat creates a very low resistance path through the bypass and most of the cooling water goes that way. Adding the valve in there restricts the bypass flow and ensures there is adequate flow though the block.

People remove the thermostats for various reasons.
1) they break and are expensive to replace
2) engine is overheating and surely if we remove the t-stat we will increase cooling? (this is incorrect thinking on an A4)
3) thermostat housing has become degraded and thermostat is no longer operating correctly.

Peter


Hi Peter!

Thank you for all that info, so it sounds like my issue is that most of the water is not cooling the engine.

It is strange that when I noticed it over-heating that I wasn't getting a lot of water out of the exhaust but when she was running at a higher RPM I was getting a "normal" (what I am using to with this boat) amount of raw water through the exhaust. Would this still be true if it's a bypass/thermostat cooling issue or could it be a blockage(maybe both)? I find it odd that I start the engine, water flowing fine and engine sound stable but after 10-20 mins of idling it will start to overheat with a lot less water coming out the exhaust and the engine is struggling to keep steady. My assumption is that at the lower RPMs the impeller isn't moving fast enough to creating enough suction to get enough water through the block (without the valve to help create pressure) to cool it and that most of the water is coming out of the exhaust. Which, over a period of time, will cause the engine to slowly overheat. BUT at the higher RPMs it floods enough water to keep it cool. Does this sound like it makes sense? haha

I am very new to this so pardon my ignorance. I am all for saving money and adding a valve to hopefully resolve my issue. Would this valve be position before the cooling line runs to the thermostat housing and after the T connection (that I think puts cold water into the block?)?

Here are two images that give you an idea of the line. From what I could see on Sunday and the images the cooling line doesn't have a valve.
https://drive.google.com/open?id=1cMVyRr2ds17H3T4Nywg_uXcBwNb52_R_
https://drive.google.com/open?id=1oXk_Qf-h28glFWGrenPQEaJSiexoQ4EG

I have done some research on the moyer forum and it is backing what you are saying 110%, I posted my issue in their forum but am waiting for it to be approved by a mod. I will let you know what i hear from them.

Thanks!!! :D
 

Jenkins

Member II
Chris,

The image below, from Moyer Marine International, show the bypass valve. It is the silver colored valve with the black handle that is connected to the brass line running to the thermostat housing.
r7.jpg


The variable water flow issue is odd.

There is a procedure for performing an acid flush on these engines. The problem is that raw water cooled engines get clogged up with dead marine critters and rust. These flushing procedures are all detailed in the Moyer Maintenance manual which the kind folks on the Moyer forum will urge you to get.

I suggest you hang a bucket over your stern and collect cooling water while the engine runs for 1 minute. Report the amount collected on the Moyer thread you have started.

Peter
 

chrisoelder

Member II
Chris,

The image below, from Moyer Marine International, show the bypass valve. It is the silver colored valve with the black handle that is connected to the brass line running to the thermostat housing.
r7.jpg


The variable water flow issue is odd.

There is a procedure for performing an acid flush on these engines. The problem is that raw water cooled engines get clogged up with dead marine critters and rust. These flushing procedures are all detailed in the Moyer Maintenance manual which the kind folks on the Moyer forum will urge you to get.

I suggest you hang a bucket over your stern and collect cooling water while the engine runs for 1 minute. Report the amount collected on the Moyer thread you have started.

Peter

Hi Peter,

Smart idea! Thank you again for the help
 

tenders

Innocent Bystander
I've described this on the Moyer site many times, but I'll put it here too for your benefit and for posterity because A4 questions sometimes do crop up. I recommend taking the thermostat completely out while you troubleshoot this problem (you've indicated the thermostat is already out), and blocking off the bypass (the hose that runs from the tee that goes into the block, to the thermostat housing) by stuffing a large-ish bolt into the hose and then reattaching the hose. The bolt is easy to pull out if and when you've solved the problem to your satisfaction...if indeed you ever want to take it out.

The bolt will force practically all the water coming out of the pump through the block and head, and out the exhaust. The engine will be "supercooled," which you might think is less than perfect, but one thing it will NOT be is overheated, which is disastrous. At least, it won't overheat due to the path of the liquid in the cooling system. If the engine keeps overheating, which seems doubtful to me given what you've described is happening, this will allow you to troubleshoot without dealing with the complication of the A4's unusual thermostat.

If you're grasping what we're talking about regarding the bypass valve, then you'll understand why the bolt solution is a nonadjustable, zero cost, 5-minute version of the bypass valve. And it's how my engine has run since 1994. The only drawback I've encountered running the engine this cold (never above 120°) is that the valves sometimes stick a little so the engine runs a bit rough, to a degree that is barely perceptible. The solution to this is to run with the recommended dose of Marvel Mystery Oil in the fuel, something like a cup per tank, which solves the problem completely.

What I particularly like about this arrangement is that if the engine is EVER warm, the list of things that can be wrong with it is quite short: plastic bag sucked up in raw water intake (happened once), closed raw water intake (happened once), gradual temperature creep necessitating acid flush (done this twice since 1994 well before it really needed to be done), or failed water pump (never happened to me). That's pretty much it, and you know something is amiss at 125° so you have plenty of time to deal with it.

There are a lot of sad stories like yours of people only realizing something was wrong when their diesel or gas engine is so hot that it starts making stuff smoke in the engine room. That's dangerous, not to mention scary. The bolt buys you a lot of time and temperature to prevent these things from becoming an issue.
 
Last edited:

chrisoelder

Member II
I've described this on the Moyer site many times, but I'll put it here too for your benefit and for posterity because A4 questions sometimes do crop up. I recommend taking the thermostat completely out while you troubleshoot this problem (you've indicated the thermostat is already out), and blocking off the bypass (the hose that runs from the tee that goes into the block, to the thermostat housing) by stuffing a large-ish bolt into the hose and then reattaching the hose. The bolt is easy to pull out if and when you've solved the problem to your satisfaction...if indeed you ever want to take it out.

The bolt will force practically all the water coming out of the pump through the block and head, and out the exhaust. The engine will be "supercooled," which you might think is less than perfect, but one thing it will NOT be is overheated, which is disastrous. At least, it won't overheat due to the path of the liquid in the cooling system. If the engine keeps overheating, which seems doubtful to me given what you've described is happening, this will allow you to troubleshoot without dealing with the complication of the A4's unusual thermostat.

If you're grasping what we're talking about regarding the bypass valve, then you'll understand why the bolt solution is a nonadjustable, zero cost, 5-minute version of the bypass valve. And it's how my engine has run since 1994. The only drawback I've encountered running the engine this cold (never above 120°) is that the valves sometimes stick a little so the engine runs a bit rough, to a degree that is barely perceptible. The solution to this is to run with the recommended dose of Marvel Mystery Oil in the fuel, something like a cup per tank, which solves the problem completely.

What I particularly like about this arrangement is that if the engine is EVER warm, the list of things that can be wrong with it is quite short: plastic bag sucked up in raw water intake (happened once), closed raw water intake (happened once), gradual temperature creep necessitating acid flush (done this twice since 1994 well before it really needed to be done), or failed water pump (never happened to me). That's pretty much it, and you know something is amiss at 125° so you have plenty of time to deal with it.

There are a lot of sad stories like yours of people only realizing something was wrong when their diesel or gas engine is so hot that it starts making stuff smoke in the engine room. That's dangerous, not to mention scary. The bolt buys you a lot of time and temperature to prevent these things from becoming an issue.


@tenders

A lot of great info here! I will make sure to close off the bypass valve. After talking to the guys at moyer they think that I have something that is clogging my exhaust manifold exit. Which would make sense since the engine runs great one minute (in rough water) and then overheats the next (in calm water). This weekend I am planning on testing the water line once step at a time. I will make sure to close off the bypass valve before and after i find the issue to my problems.

It was not fun starting to see smoke come out of the engine room but luckily my crew and I caught it early

JUST SAW YOUR REPLY TENDERS on MOYER THANK YOU!!!!
 
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chrisoelder

Member II
Resolved!

Hi All,

Thank you for all the help and support. At the suggestions of you all and the people at Moyer, I performed an acid bath and capped off the thermostat bypass. Ran he for an hour without overheating! Took her around the marina yesterday and she ran beautifully.

Just now figuring out a few issues when motoring out in the bay but I think I found the solution to my problem, an open-air valve connected to my water cooling line

Thanks!!!
Chris


NOOB QUESTION: how do i set up my signature area on here? I see some of you with your boat name, size, engine and location
 

JPS27

Member III
Sounds great, Chris. For signature, go to settings and then it's on the left hand side in a box of options.
 

Max McFarlane

New Member
Hi there, I’m having a similar issue. I have a 1970 Ericson 29 with a gas Atomic 4 engine.

Here is my issue. When I’m at the dock I start the motor and it runs great. No overheating issue at all. I put it into gear and run it at full blast tided up at the dock for 20 - 30 minutes and the temp gauge barely goes over 120F then I pull the boat out of my slip take it out of the marina and it’s still only 120F - 130F everything is great. She’s pushing along at 5 knots. Once we get out to sea I put the sails up and shut the motor off. Sail for 2 hours up and down the coast. Then once I’ve pulled back into the channel I turn the motor on and take down the sails after 3 minutes of running the engine I notice much less water coming out of the back and the temp is climbing fast 180, 190 then 200 +. I shut the engine off and put the main sail up and sail back into my slip once I get back to my slip I start the motor and Its still over heating. So I hook up the fresh water hose on my dock to the clean out to run fresh water through the motor and instantly cools back down to bellow 120F and it’s shooting water out the back now, this takes care of the over heating problem until I take the boat out again I’ll cruise out of the marina no issues then I’ll shut the motor off, sail then when I come back in of course same thing happens starts to over heat. this has happened about 7 times every time I take the boat out. It never over heats at the dock only when I’m coming back in after a sail.

One time I took it out to go to the pump out after a sail and it started over heating again to 180 - 190 + but I started revving the engine and something happened, some how it started cooling again and it was fine went to the pump out then motored back to my slip temp was 120F

here is what I’ve done to try to handle the issue.

-New head and gaskets (Moyer)
-New impeller
-Vented loop on the exhaust exit because I thought it might be too much back pressure while out at sea. (Didn’t work)
-New Manifold (Moyer)
-New carburetor
-New Spark plugs
-New spark plug leads
-Sea strainer clean
-Thru hull fully open and clean
- Put a brand new thermostat in (Moyer) but then took it out again because it didn’t handle the issue. I’ve been running with no thermostat and I do not have the bypass shut off.

I just ordered a brand new water pump from Moyer, thinking that might help. But I don’t know anymore. Hope you guys can help!
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
No A4 experience have I, but my initial thought is that the raw water pump, specifically the impeller, has something wrong.
Best of luck to you in trouble shooting this.
The water pump is the small "achilles heel" of every marine diesel or gas engine, it seems. :(
 

tenders

Innocent Bystander
If you're running without a bypass valve, and without a thermostat, the problem is that the cooling water is going through the bypass and not through the engine. You have to have one or the other! That's why it's called a bypass - it's bypassing the engine!

My guilty secret is that I've been running a cold engine for decades with a bolt stuffed into the short hose that goes from the tee after the water pump to the thermostat. It in essence functions like a permanently-closed bypass valve. The head of the bolt just barely fits into the hose, and of course the whole shaft of the bolt fits in. Find you a bolt like that and see if your cooling problems are solved. Then decide if you want a bypass valve, a thermostat, or...keep the bolt.

Now, why you're getting "much less water" out the exhaust, I'm not sure. Maybe you have an exhaust blockage, maybe you should give it the muriatic acid (or vinegar) treatment described in detail on the Moyer forums. It could be that the shoe inside the pump is worn, or the plate that covers the impeller is worn, and doesn't compress the impeller enough to push sufficient water, or leaks around the edges of the impeller. Or maybe it's all in your mind. I would squarely address the bypass situation first, then reevaluate
 

Max McFarlane

New Member
I was reading one of your earlier posts about the bolt / bypass and a lightbulb went off in my head about the bypass. I’m gonna try that and see if it works. It’s just a weird issue, do you know why it would only overheat after I’ve turned the engine off at sea and turned it back on again after sailing? It doesn’t overheat at the dock ever…

I agree the pump is an achilles heel that’s why I was thinking maybe this older pump is warped slightly and that’s allowing the water to get past the impeller and decreasing the pressure maybe? Figured a new pump would at least check that off the list.
 

tenders

Innocent Bystander
The Moyer pump is a better design than the original pump and yes, will immediately address any pump related issues. It’s pretty expensive, though. Depending on how much money you want to throw speculatively at the problem, you can also replace the compression shoe in the original pump (sold by Moyer) and grind the inside of the OEM cover plate flat again using some wet/dry sandpaper on a piece of glass.
 
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