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Old 10-11-2019, 22:31   #1
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Atomic 4 - Shutdown Procedure

Hi - I'm a new boat owner and my boat has an Universal Atomic 4 gasoline engine. I'm trying to find the optimal shutdown procedure for this engine. I'm wondering specifically about when to shut down the seacock for the raw water intake.

The manual reads:
"Before stopping the engine, close the throttle and disengage the clutch. Allow the engine to idle for a minute or so before turning off the ignition. Stopping in this manner will permit excessive heat to be absorbed by the cooling system."

For startup procedures, the manual says to open the seacock prior to pushing the starter button but from what I've read, this isn't optimal since it may allow back-flooding if there are ignition issues. I've also read that if there are no ignition issues, not having the seacock open may lead to impeller damage. Since my engine starts on the first try, I plan to have the seacock open as per the manual's recommendations.

However, I'm not sure what the sequence for proper shutdown is as far as the seacock is concerned. If I close the seacock after shutting down the engine, do I run the risk of the back-flooding that some people were concerned about? If I close the seacock prior to shutting down the engine, do I risk the impeller? Aside from mentioning the seacock during startup, the manual is silent on what to do with the seacock during the shutdown procedure.
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Old 10-11-2019, 23:53   #2
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Re: Atomic 4 - Shutdown Procedure

If you were running the engine hard before shutdown, then you need to let it idle for maybe 10 minutes. Usually docking, most leave the engine run until all lines are set. That's usually enough time to shutdown. The seacock should be open when you're going to start, but shut if you have starting issues. Otherwise cranking with no exhaust pressure can cause raw water to back up the exhaust an flood one or more cylinders. Close the seacock if you have starting issues, but don't forget it's closed.

When you're done running the engine, shut the seacock. Don't run the engine with the seacock closed. The impeller has residual water that will lube it for maybe 30 seconds to a minute. After that you'll burn up the impeller.
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Old 11-11-2019, 00:49   #3
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Re: Atomic 4 - Shutdown Procedure

A great question, just let the engine cool a bit after docking... but in my case I'm putting to our slip, so I have no worries about cooling.

I also don't close my engine seacocks (yes, I'm sure I'm going to take "feedback" on that ) but I also have freshwater cooling... and a new heat exchanger.

During starting, if your A4 is hard starting... I would close the intake cooling seacock during starting. Once it's starts... open the seacock and check the flow out the stern.

A few great resources for A4 engines:

For advice:
Moyer Marine Atomic 4 Community - Home of the Afourians - Powered by vBulletin

For parts and upgrades:
http://www.moyermarine.com/

For more upgrades, including an awesome thermostat solution:
Atomic 4 - Indigo Electronics, Inc.
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Old 11-11-2019, 02:32   #4
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Re: Atomic 4 - Shutdown Procedure

Water flow through an engine-driven impeller-type water pump is directly related to engine crank speed. It is a feature that helps put the right amount of cooling water into the system to match the amounts of heat built up by the engine, and the amounts of exhaust gasses flowing out through the system. This is also why replacing with an electric pump is a really bad idea but that is topic for another thread.

At idle, and crank-over speed the amount of flow is minimal compared to full-rpm operation. Unless you are cranking on the thing for a minute or more you aren't going to be needing to worry about backflow into the engine with overflow water from the exhaust system. Even at idle or crank-over speed there is still some exhaust flow as the cylinders are still pumping non-fully combusted air through the system, helping push the water through with it. The water build up issue is way overblown in the sailing community. It exists, but isn't as big of s deal as many fear.

You are going to start having starter issues before that and should stop cranking after 15-20 seconds maximum anyhow to not overheat that compact motor. Starters are not designed to run continuously and it is really hard on them to do that. If it doesn't start after the second attempt, then perhaps think about shutting the intake water seacock off temporarily until you can get it to start. Figure out what is wrong, fix it add/or tune the darn thing up. A properly maintained engine should reliably start after a few cranks.

It's a good idea to turn off the seacock at shutdown if you are going to be leaving the boat. It is just good practice and seamanship, as with all seacocks when unattended. It's your boat though. But there is really no reason to shut it off when you are sailing after having motored out from the slip/mooring and have shut down the engine to be a sailboat once the sails ate raised.
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Old 11-11-2019, 09:57   #5
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Re: Atomic 4 - Shutdown Procedure

My C&C had a placard stating "Good seamanship dictates that all seacocks except engine intake be closed when the vessel is unattended."

I understood this to mean that ideally everything would be closed, but the chance of starting the engine (which could be done without entering the boat) with the intake closed was too great a risk. Especially if, say, the boat was moved by marina staff or others during an emergency (we had a fire at a nearby slip once). So the engine intake stays open.


Also, for anyone who hauls out and winterizes where it freezes - make sure all seacocks are OPEN, or at least opened and drained prior to closing. The stainless ball is very strong. The little cylinder of water trapped in that ball while the valve is closed, is also very strong - stronger than the valve body. I split a valve body once after a sudden freeze, fortunately in an irrigation pump and not the boat.
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Old 11-11-2019, 10:39   #6
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Re: Atomic 4 - Shutdown Procedure

I second Reline452's answer. Leave the engine intake open. Don't close it, unless you plan on being away for weeks, and then put a big red lettered sign taped over the starter button reminding you to open it up again.
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Old 11-11-2019, 11:46   #7
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Re: Atomic 4 - Shutdown Procedure

Quote:
Originally Posted by SeaHarlequin View Post
Hi - I'm a new boat owner and my boat has an Universal Atomic 4 gasoline engine. I'm trying to find the optimal shutdown procedure for this engine. I'm wondering specifically about when to shut down the seacock for the raw water intake.

The manual reads:
"Before stopping the engine, close the throttle and disengage the clutch. Allow the engine to idle for a minute or so before turning off the ignition. Stopping in this manner will permit excessive heat to be absorbed by the cooling system."

For startup procedures, the manual says to open the seacock prior to pushing the starter button but from what I've read, this isn't optimal since it may allow back-flooding if there are ignition issues. I've also read that if there are no ignition issues, not having the seacock open may lead to impeller damage. Since my engine starts on the first try, I plan to have the seacock open as per the manual's recommendations.

However, I'm not sure what the sequence for proper shutdown is as far as the seacock is concerned. If I close the seacock after shutting down the engine, do I run the risk of the back-flooding that some people were concerned about? If I close the seacock prior to shutting down the engine, do I risk the impeller? Aside from mentioning the seacock during startup, the manual is silent on what to do with the seacock during the shutdown procedure.
Open it before you start and shut it after you turn the engine off. A good practice is to check for an overboard discharge after starting.
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Old 11-11-2019, 11:51   #8
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Re: Atomic 4 - Shutdown Procedure

I started off with a question and got an answer as well as tons of great information and advice. I appreciate all of your help. Thank you very much!
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Old 11-11-2019, 13:24   #9
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Re: Atomic 4 - Shutdown Procedure

I have an A4, and most of the time it will start right up. If I have to crank it more than a combined total of 30 seconds, I close the intake seacock until she kicks.

In the Catalina 30, the engine is located under the dining settee, and the cushion and support board must be removed to get to the intake seacock. I routinely open this up before attempting to start, and I check the oil level as well. Once started, and having confirmed water batching out with the exhaust, I'll take one last look (checking the raw water pump for drips) and close up the settee.

You'll get opinions on both sides re closing the intake seacock. A few posters on the Moyer A4 forum always shut them, so they leave the engine key hanging on the valve handle.
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Old 11-11-2019, 13:36   #10
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Re: Atomic 4 - Shutdown Procedure

Quote:
Originally Posted by BlackHeron View Post
(snippage)
The water build up issue is way overblown in the sailing community. It exists, but isn't as big of s deal as many fear.
In general, I agree that it's overblown, but I would add that if you need to be certain of the condition of the exhaust elbow. A partially blocked elbow will drastically raise the chance of filling a cylinder with water.
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Old 11-11-2019, 17:28   #11
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Re: Atomic 4 - Shutdown Procedure

Its OK to shut the seacock IF YOU HANG YOUR IGNITION KEY ON THE HANDLE OF THE SEACOCK. Then you'll never forget to open it before starting
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