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Atomic 4 dies under load

Hi,

I have an Atomic 4 in my new to me Catalina 30, and have an issue with my A4 all of a sudden dying once I put it into gear.

This issue cropped up after I replaced my alternator belt which broke during a recent long period of motoring, I ended up running the engine on the batteries until it died completely and sailed the rest of the way home. I replaced the alternator belt, and have now had issues when I put it into gear. I can feather the throttle to get it into gear, but in forward it dies almost immediately once fully in gear. I can get it fully into reverse but cannot generate much power while in gear. There have been no issues with starting it up or while idling in neutral.

Here are the trouble shooting steps I've taken so far:
1. went swimming to ensure the prop is not fouled - it is not
2. replaced the fuel filter - old filter appeared clean after dumping the fuel from the filter
3. checked that stuffing box has a decent drip

What should I check next? I'm at a loss since there was no issue prior to replacing the alternator belt - which I would think was not related...

Wracking my brain, I am about due for my 50 hour oil change. But again, don't see how this can be related since it was running without issue previously.
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Re: Atomic 4 dies under load

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Originally Posted by Anchor1800 View Post
Hi,

I have an Atomic 4 in my new to me Catalina 30, and have an issue with my A4 all of a sudden dying once I put it into gear.

This issue cropped up after I replaced my alternator belt which broke during a recent long period of motoring, I ended up running the engine on the batteries until it died completely and sailed the rest of the way home. I replaced the alternator belt, and have now had issues when I put it into gear. I can feather the throttle to get it into gear, but in forward it dies almost immediately once fully in gear. I can get it fully into reverse but cannot generate much power while in gear. There have been no issues with starting it up or while idling in neutral.

Here are the trouble shooting steps I've taken so far:
1. went swimming to ensure the prop is not fouled - it is not
2. replaced the fuel filter - old filter appeared clean after dumping the fuel from the filter
3. checked that stuffing box has a decent drip

What should I check next? I'm at a loss since there was no issue prior to replacing the alternator belt - which I would think was not related...

Wracking my brain, I am about due for my 50 hour oil change. But again, don't see how this can be related since it was running without issue previously.
My initial reaction is that this is a fuel problem. My first guess is that you ended up with a small air leak in the fuel system when your replaced the fuel filter. That would allow adequate fuel delivery at idle, but a mix of air and fuel at higher RPM's. My next set of guesses are also related to the filter change and perhaps you either got an airlock in the fuel line when you replaced the filter or some gunk in the line. I like the gunk in the line theory since that could clog the main jet in the carburetor, in which case the main jet needs to be cleaned since it starts and idles well on the idle jet but does not run well once the main jet is needed. (Hint: before doing anything serious with the main jet, look at its position then carefully turn it all the way in against the seat carefully counting the turns and partial turns. That should be a good starting setting when you put it back after clearing it.)

Other possibilities would be a clogged or sticking float valve,or a bad fuel pump (especially if you have an electric fuel pump rather than the mechanical one since you also had electrical issues). On the electrical side, its possible that the ignition is not advancing or you burned the points (a common occurrence if you don't have the newer 'pointless' electronic ignition system. We used to save match book covers and run them through the points to clean them periodically on our Universal Blue Jacket.)

Jeff


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post #3 of 39 Old 10-08-2018
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Re: Atomic 4 dies under load

It's been a VERY Long time since I had an A 4 , but I think we can rule out oil. I would pull the coil wire and check that you're getting good spark. Could be a coil or condenser, I do seem to recall buying coil wires for my A 4 that were even bad right out of the box. Check rotor, cap and points, Sometimes there are hairline cracks that are barely visible in the cap and rotor. Then check all the ignition wires, plugs, and Ignition timing. That's all I've got, hopefully, a better mechanic than me will chime in.

Oh, and keep us posted on your progress!

Last edited by tempest; 10-08-2018 at 04:17 PM.
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Re: Atomic 4 dies under load

I'm leaning towards jet\fuel problem as well. I've never taken apart an A4 carb but have done tons of carbs on small and large engines over my life. Odds are the main jet is clogged (aka high jet). Some carbs have a low and a high jet, some just use a pilot screw system as a low jet and a main jet as a high. The important part is that the "low" system sets idle, the "high" system feeds the fuel needed to drive the engine under load to higher RPM.

With a blockage in the high system (most likely the jet) the engine will stall when put under load as the fuel supplied by the low system is usually just enough to hold idle while in neutral. As soon as the load is added the small amount of fuel\air supplied can't hold the engine up to even an idle RPM anymore and stalls out.

At any rate before pulling the carbs I would check the spark plugs to see their condition. If worn away or of unknown age I would replace them regardless. Check them for heavy sooting (running too rich), or white ash (way too lean) as that can indicate other problems as well with the fuel system. I'm not sure how hard it is to remove the A4 carb but I would pull it to clean the jets, do not rely on "in the tank" chemicals that claim to clean carbs, they rarely work and can actually damage other parts.

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Re: Atomic 4 dies under load

Probably a main jet fuel issue but if you don't have the upgrade to ignition ,good thing to do it. If the alternater field is connected to coil maybe change some connections. (volt dropage at coil) condenser failing? Some carbs have a screen right in the fuel inlet (never looked at) Cam operated fuel pump?? (air leak or just worn out) Float level ?? Needle /seat important as that what keeps the bilge from filling with gas
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Re: Atomic 4 dies under load

It may be related to fuel but then you did run the engine on very low voltage until it died. Might want to start with the spark plugs and points. the lower the volts the higher the amps drawn from the ignition components. might have overheated some component like the coil. what else does the v belt drive on your engine, Cooling water pump?

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Re: Atomic 4 dies under load

I'm with Jeff. And while I don't suggest randomly throwing time or money at things in order to fix them, carburetors really should be broken down and overhauled maybe every five years. If yours hasn't been, then it is time to overhaul it completely, which will also eliminate fuel clogs, etc. as the problem.

If you're not familiar with the process, basically you need a gallon can of Gumout to soak things with, common hand tools, and maybe four hours of patiently disassembling and reassembling. And a rebuild kit. A "major rebuild kit" if you can find something labeled that way. The job isn't hard--but some precision and care is needed to make it right.
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Re: Atomic 4 dies under load

I've taken the A4 carb apart many times when I had my old Catalina 27 - nothing to it, but the float level is a bit tricky to set.

If your engine has an electric fuel pump, which many have been updated to, there is a 10-amp inline fuse that connects to the pump, usually connected to the coil's hot line. It may be blown. Usually, the engine will start fairly easily, but eventually die from fuel starvation. I've blown this fuse twice.

Good luck,

Gary
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Re: Atomic 4 dies under load

Will the motor stall/shut down if you just let it idle for a while without shifting into gear? Here's why I ask.
I had an intermittent connection to the electric fuel pump. Engine would die as you described. Once it got so bad, the engine would start and run for about 90 seconds, then die. Wait a minute, restart and it would run for about 90 seconds and die again. The fuel was refilling the carb without the fuel pump running but it didn't have nearly enough flow to keep up. Once we connected the pump directly to the battery and it ran fine we knew we had tracked down the issue. Traced the power line to the fuse and found a broken crimp. As others have mentioned, it could be spark related (coil,rotor,points,wires). Is it possible that in messing with the alt belt you moved plug wires and put them back on in the wrong firing order?

s/v Harmony
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Re: Atomic 4 dies under load

you are going to need this.....
https://moyermarine.com/

they have a forum with tons of information AND they are the most helpful people you will ever talk to on the phone. I have had a couple of 1 hour calls with them as we diagnosied a problem together. Seriously, i cant say enough good things about them
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