Atomic 4 Throttle - SailNet Community
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post #1 of 10 Old 08-12-2013 Thread Starter
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Atomic 4 Throttle

I was motoring a narrow channel and noticed I was going a little slowly so I gave it more throttle. I noticed that idle worked and maybe 1/4 throttle worked but pushing the lever further made no difference.
The engine would typically race if I gave it a lot of throttle. This time the rpm stayed at about 1/4 or less.

Once out of the channel I shut off the engine and checked the throttle cable.
I checked that it operated smoothly throughout its full throw.
The casing seemed to be securely fastened to the block. The center wire was securely fastened to the throttle lever.
The throttle lever was securely fastened to the axle that it attaches to.

After playing with it but not really doing anything I started up the engine and it worked fine for several hours till the end of the sail.

What do you think happened?

The throttle assembly was recently replaced and it works smoothly.

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It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.

Last edited by davidpm; 08-12-2013 at 05:00 PM.
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post #2 of 10 Old 08-12-2013
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Re: Atomic 4 Throttle

I think you picked up something on your prop.
Seaweed, a plastic bag, or something else on the prop can cause the engine to labour, which does not allow it to achieve 'normal' RPM.
While you were playing with it, the boat was still slipping along with the prop still (or idly spinning, or FOLDING?) and the whatever it was fell off.

Is this a possible scenario given the waters you were in at the time?

Andy
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post #3 of 10 Old 08-13-2013
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Re: Atomic 4 Throttle

Tack ?

I get 4 knots at 1000+ RPM and make pretty much max speed at about 1400 RPM of 5.5 knots

I have NEMA 2000 fuel flow and the fuel burn goes form .5 GPH at 1000+ to 1 GPH at 5.5 knots

The boat will go faster BUT the stern just sinks and it uses fuel like crazy at 6.2 knots

All of this is with a 12 X 7 two blade flex-o-fold

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post #4 of 10 Old 08-14-2013 Thread Starter
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Re: Atomic 4 Throttle

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Originally Posted by aelkin View Post
I think you picked up something on your prop.
Seaweed, a plastic bag, or something else on the prop can cause the engine to labour, which does not allow it to achieve 'normal' RPM.
While you were playing with it, the boat was still slipping along with the prop still (or idly spinning, or FOLDING?) and the whatever it was fell off.

Is this a possible scenario given the waters you were in at the time?

Andy
I thought of that but I would have thought that the engine would have changed it tone in some way as I advanced the throttle.
Idle was noticable. 15% was noticeable but their was no change is sound from 15% to 100% throttle position.

I'm leaning to casing came adrift in the binnacle and eventually got jammed enough to work.

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It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #5 of 10 Old 08-14-2013
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Re: Atomic 4 Throttle

You can put some light weight oil like MMO on the inside cable of the Teleflex cable.
MMO is also a rust inhibitor/preventer.

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post #6 of 10 Old 08-14-2013
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Re: Atomic 4 Throttle

Exhaust could be partially blocked. Flaking metal in a raw water cooled engine can cause a temporary blockage. A collapsing exhaust hose. etc...

Fuel issues, air or spark issues. My old A4 ran once on fuel so bad it looked like chunky soup when I pulled the carb apart, would not rev very high but kept plugging along.

One of the great things about those engines is that they will keep running, just run like crap.

There are many possible answers. You need to duplicate the problem so you can trouble shoot.
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post #7 of 10 Old 08-15-2013 Thread Starter
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Re: Atomic 4 Throttle

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You can put some light weight oil like MMO on the inside cable of the Teleflex cable.
MMO is also a rust inhibitor/preventer.
It is a new cable and is very smooth operating. Thanks for the thought though.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #8 of 10 Old 08-15-2013 Thread Starter
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Re: Atomic 4 Throttle

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Exhaust could be partially blocked. Flaking metal in a raw water cooled engine can cause a temporary blockage. A collapsing exhaust hose. etc...

Fuel issues, air or spark issues. My old A4 ran once on fuel so bad it looked like chunky soup when I pulled the carb apart, would not rev very high but kept plugging along.

One of the great things about those engines is that they will keep running, just run like crap.

There are many possible answers. You need to duplicate the problem so you can trouble shoot.
It is fresh water cooled.
But the fuel idea is interesting. He did replace the fuel pump recently. I guess if something is blocking the fuel even with the throttle working perfectly it would still cause the rpm's to be low with no lugging.

We did remove the fuel tank and clean it etc at the beginning of the season.
But he did have fuel issues for the last couple of years.

I'm pretty sure I know when the problem will be duplicated. At the worst possible moment.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #9 of 10 Old 08-15-2013
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Re: Atomic 4 Throttle

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It is fresh water cooled.
But the fuel idea is interesting. He did replace the fuel pump recently. I guess if something is blocking the fuel even with the throttle working perfectly it would still cause the rpm's to be low with no lugging.

We did remove the fuel tank and clean it etc at the beginning of the season.
But he did have fuel issues for the last couple of years.

I'm pretty sure I know when the problem will be duplicated. At the worst possible moment.
FWC as in it has a heat exchanger?

If the main jet in the carb gets blocked temporarily you will just have idle speeds available. If you have the Zenith carb you can remove the 1/2" main passage plug that drains the gas out of the carb. Catch the fuel in a clean container and look for crud; even small specks can cause problems.

Good thing you cleaned the fuel tank. They can get really nasty if left for years...

Worst possible moment is always when you will find it again. Were the fuel lines replaced as well? They can corrode from the inside because of the Ethanol in the gas. Your tax dollars at work!

Pic is what was at the bottom of our fuel tank.
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Last edited by CalebD; 08-15-2013 at 01:09 AM.
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post #10 of 10 Old 08-15-2013
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Re: Atomic 4 Throttle

I have a similar problem. Do you have to have a certain amount of choke and throttle combination to start it? I just chaulk it up to being a finicky old Atomic 4. Mine is going to do what it wants to do, and will let me know if I am not working it right. It is an engine with a personality!
But, it will run all day without complaint if you can find that sweet spot in the throttle. Weird.
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