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HMSVictory 07-31-2016 11:26 AM

atomic 4 mini explosion
 
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went on my friend's "new" columbia 1962 29'...in real piece condition with blown out torn up sails and the one concerting aspect of the sail to me being a supposedly reliable atomic 4...
guy who owned the boat before jury rigged a lot of stuff on it, didn't really take care of big problems and after being hard to start the first problem was a screaming alternator belt. But it sounded very irregular thhe whole time, and more so as the sail went on. eventually the motor just went out of control, screaming, making crazy noises of things breaking down and propellers spinning hubs and all kinds of craziness, and we had to just kill it or it might have died on its own can't remember exactly. But without the motor, we were drifting in to shore, and eventually at anchor decided we had to try and start it again. After a few tries we did get it started, only to put it into gear rev it, have it make some crazy noises for a few minutes, then make a loud and powerful explosion in the compartment (no flames that we saw) and fill the boat with smoke for the next 10 minutes even after turning it off and killing the battery switch. ..what in the hell happened? Ideas? I don't know these motors.. do they have a release valve in case of too much compression or something? blown gasket? blown piston ring?

EDIT: even at WOT the A4 barely moved her. Apparently these are 30HP engines. Even with a reef on the bottom it should push a boat more than 4 kn... So I'm wondering if blow by and resulting carbon buildup could have been catching

Ulladh 07-31-2016 12:20 PM

Re: atomic 4 mini explosion
 
Victory

You need to find some new friends.

Maybe even some that know how to maintain their boats and not create more derelicts.

Gasoline combustion engines over reving and irregular firing is more than likely a build up of carbon deposits causing pre-ignition.

Loud "explosion"was probably pre-ignition while intake valve was open, or build up of uncombusted fuel in exhaust igniting.

Your friend needs at the very least an engine rebuild.

Jeff_H 07-31-2016 01:30 PM

Re: atomic 4 mini explosion
 
Also, if the timing is too far advanced the engine can backfire through the carburetor. It sounds terrible, can make lots of smoke but its at least less serious than an engine rebuild. My comments are predicated on the probability that this engine does not have an updated ignition system.

The statement, "But it sounded very irregular thhe whole time, and more so as the sail went on. eventually the motor just went out of control, screaming, making crazy noises of things breaking down and propellers spinning hubs and all kinds of craziness, " seems extremely unlikely but not imposible. But in any event you are describing a wide range of symptoms that could result from all kinds of causes.

For example, the combination of an engine going out of control and the 'propeller spinning hubs' sounds more like badly adjusted controls so that the throttle was not backing off, and the transmission was not fully in gear. This is simple top diagnose and repair.

There are a whole host of things which could make the engine display the symptoms that you descibe. Without being there its hard to say what the actual cause is. My initial sense is that this is a problem with the ignition system but can't say whether the points are fried or improperly adjusted, the points mounting plate is loose and needs replacement, the distributor cap is cracked, the distributor clamp is loose and the distributor has been left free to rotate, whether the coil is on the way out, whether points cam is worn past its 'use by date', whether the timing gear is shot or improperly timed, whether there is one cylinder that is not reliably firing eventually flooding and so on. It is also possible that the engine is running rich which can also cause backfires, or lean which could cause run on and foul smelling smoke on shut down.

The carboned-up problem that was mentioned is also a possibility.

But, Properly maintained Atomic 4's are amazingly reliable and easy to maintain, but they take basic maintenance and enough knowledge of engines to quickly diagnose when something typical of these engines does occur.

Jeff

Capt Len 07-31-2016 02:15 PM

Re: atomic 4 mini explosion
 
My first thought was 'Is the leg being pulled'

wrwakefield 07-31-2016 03:05 PM

Re: atomic 4 mini explosion
 
My first sailboat had a gasoline fired atomic 4 way back when. It was very quiet and reliable, and easy to maintain.

The engine and transmission shared the same motor oil and sump, and there was no oil filter, so routine oil changes were a must. [IIRC every 40 hrs or 6 months, but verify that...]

Also, that engine required leaded gasoline, so I had to put a lead additive in unleaded gas when in the US.

When I took that boat to Mexico, at that time you could still buy leaded gas at the pumps... In fact, sometimes the 'unleaded' pump was dispensing leaded gas. [I blew up the catalytic converter on my VW van in Mexico that way...]

I mention both of these facts as possible contributing factors in case prior owners were unaware and ignored these requirements.

Cheers!

Bill

JimsCAL 07-31-2016 05:33 PM

Re: atomic 4 mini explosion
 
Is the same guy that was going to tow the Mac 65 Zeus to Miami?

Capt Len 07-31-2016 09:09 PM

Re: atomic 4 mini explosion
 
The old time leaded gas lubricated the valves New unleaded eventually burned the old time exhaust valves but this takes longer than even a slow learner figuring it out .Maybe

travlin-easy 07-31-2016 11:10 PM

Re: atomic 4 mini explosion
 
If you read the Moyer Marine A4 repair manual, you will find that a product called Marvel Mystery Oil is highly recommended as a fuel additive. It's a top cylinder lubricant that helps clean and seat the valves, and I, as well as every A4 owner I know, use this stuff religiously. Just 2 ounces per 10 gallons and the A4 runs like a Swiss watch.

Good luck,

Gary :cool:

Lazerbrains 08-01-2016 09:08 AM

Re: atomic 4 mini explosion
 
Quote:

Originally Posted by JimsCAL (Post 3599697)
Is the same guy that was going to tow the Mac 65 Zeus to Miami?

I remember back when he was going to sail a Sunfish for 60 miles in one day - I wonder whatever became of that adventure???

Capt Len 08-01-2016 11:16 AM

Re: atomic 4 mini explosion
 
When the old girl finally fails you replace the valves and seats with 'stelite' during rebuild. Admit I don't know if A4's are eligible for this treatment as my experience is mostly automotive. An aside... when the Canadian gov't banned tetra ethyl lead ,we the people paid big to the producer in Cal for their loss of revenue. (figure a bit of drift in this thread keeps up the interest)


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