Atomic 4 - RPM Drops, Then Comes Back Up

[caliman]

Hello -
I have a curious issue with my Atomic 4 on my Ericson 27.

Periodically as I leave the channel to go sailing I will experience a drop of about 20% in RPM/power for a couple minutes or so, then it goes back to where it was. When it drops, I notice the AMP meter goes way up to about 5 from just above 0.

When the RPM/power goes back to where it was, the AMP meter goes back down to just above zero.

This happens more often when first using the motor rather than later. Although it does happen when hot too.

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What I have done (within the last two years):
- New ignition coil, new points, cap, spark plugs, spark plug cables
- Set timing per manual
- New fuel line
- New fuel filter (just changed over the winter - old one was not dirty)
- New muffler and exhaust pipes

I recently tested the alternator and it passed just fine bringing in 15v at slightly above idle throttle. It is the original alternator though.

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The motor otherwise works well, idles well and starts easily.

What causes this drop in power? Is this normal or can I fix it?

Thanks in advance!

matt

[Boasun]

Have you checked your voltage regulator?? And the other compotents of your electrical system? A heavy drain on the altenator will pull your engine RPMs down.

[caliman]

Good question - I have not checked the regulator - I am not sure where that is actually.

[pschoonveld]

I agree. It sounds like the alternator is kicking in and dragging down.

Most A4s have internal regulators in the alternator. Your best bet is to pull it and find a local generator shop. An automotive parts store can test it, but most likely won't understand how it actually works and what to look for in low rev, high output alternators. They frequently deal in funky alternators like those for the A4 and deep cycle batteries.

If it's more than 10 years old and has the subsequent hours on it, you might just be best off getting it rebuilt regardless. Many small shops can put in higher performance bits and pieces to drive up the power, which is usually worth it.

Incidentally, I have an E27 with an A4 and just got done (hopefully) chasing out my charging issues. I found my local generator shop more useful and significantly less expensive that swapping parts with Moyer. Having said that, Moyer Marine is the place to go when you need A4 wisdom or parts.

[SEMIJim]

Originally Posted by caliman

Periodically as I leave the channel to go sailing I will experience a drop of about 20% in RPM/power for a couple minutes or so, then it goes back to where it was. When it drops, I notice the AMP meter goes way up to about 5 from just above 0.

When the RPM/power goes back to where it was, the AMP meter goes back down to just above zero.

You're not running a refridgerator or air-conditioner, mayhaps?

Jim

[caliman]

Thank you.

I have had thought my alternator has needed attention for some time. I was surprised it puts out a decent charge from what my meter says and that gives me pause but it still is suspect to me. Simply, it is dirty as hell. Perhaps this affects it, perhaps not. I am not sure? Anyway, I always thought a modern alternator and regulator would be a nice upgrade. At the same time, I see what you are saying about just having it rebuilt. That would certainly help I bet. Check out these pics (sorry - nite time flash light plus cabin lights!

[caliman]

Originally Posted by SEMIJim

You're not running a refridgerator or air-conditioner, mayhaps?

Jim

No I am not Jim.

[imagine2frolic]

Have you tried feathering the choke? If that keeps the rpm's up. Then the carb may need cleaning.......i2f

[caliman]

Originally Posted by imagine2frolic

Have you tried feathering the choke? If that keeps the rpm's up. Then the carb may need cleaning.......i2f

I have not done this. I have never cleaned the carb. I suspect it needs it too. I am soaking up the courage to do so.

[caliman]

Originally Posted by Boasun

Have you checked your voltage regulator?? And the other compotents of your electrical system? A heavy drain on the altenator will pull your engine RPMs down.

A year later - I owe a huge belated thankyou to Boasun - it was the regulator. Cost me only $50 for a new regulator installed - runs flawlessly now. Big thanks!!