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  #1   IP: 152.163.100.136
Old 12-08-2004, 11:08 PM
sundowner
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Engine running "fine" until it stopped suddenly within a few revolutions.

I had hoped cleaning carburetor was my only problem. When running I had more power, but there was a "pounding" noise, as though at the top of each stroke a valve was tapping the top of the piston. Oc course I know that is not possible; I'm just trying to describe the noise.

Anyway, it was consistent, and I lived with it. One problem is that it has been so long since I have had my Atomic 4 running the way I'd like that I have forgotten what it was supposed to sound like. Now I think I may have a "big" problem.

Returning to the marina, the "pounding" noise suddenly became louder, and in several revolutions the engine had stopped. I called for a tow to the marina and on arrival went home--with an unhappy feeling, that I had thrown a rod.

Today I went back to the boat and this is what I find. I can rotate the crankshaft, the pistons move up and down as scheduled, there is compression tested with my finger, the valves are all in place and moving up and down.

However, when I change the direction of rotation, there is 20 degrees of free motion before the distributor rotor starts moving in the opposite direction and before the camshaft starts to move.

So I know there is a gear on the crankshaft that drives both the camshaft and the distributor-waterpump gears. It would seem that has to be the problem. Is it keyed to the crankshaft?

Can I check anything without removing the engine? My recollection is that everything is inside, except on the ignition side. I'm wondering if I can remove the ignition side assembly and see anything that may give me a clue.

Of course what I am hoping is that this is a well known problem and there is a solution.
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  #2   IP: 204.157.20.43
Old 12-09-2004, 10:32 AM
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Sundowner,

Regrettably, I can't give you any assurances that your condition is in any way "well known", or even that things will turn out well for you.

From the basic description of your shutdown, it would be easy to assume (as you apparently did) that a rod may have failed and bound up the crankshaft. Yet this assessment is inconsistent with your finding of compression (presumably normal) in all cylinders.

I don't believe that your discovery of a 20 degree lag in the rotation of the distributor rotor, when changing direction of rotation of the crankshaft, is significant. While it's difficult to quantify, there is normally quite a bit of combined play between the crankshaft gear, the idler gear, the accessory drive gear, the distributor gear and in the distributor shaft and rotor assembly itself. Allowing for a little flexibility on the low side of your 20 degree observation, I don't believe your condition is abnormal, and I don't immediately see anything in that finding that would account for the loud mechanical noise and engine stoppage.

Having said all that, I recommend that you check the following items and let us know what you find:

1) Move the shifting lever through forward, neutral, and reverse a couple times, with the engine not running, to check for normal feel of the shifting mechanism.

2) Remove the cover of the reversing gear and turn the prop shaft with the engine in neutral to check for freedom of movement. While turning the prop shaft with the engine in neutral, you should observe the round housing of the gear cage assembly rotating within the reversing brake band.


3) Install one spark plug at a time on each cylinder, turning the starter over a few times on each cylinder. The purpose of this diagnostic is to create compression in each cylinder sequentially, to see if you can create a noticeable mechanical noise, which would give an indication of a major rod bearing failure in that particular cylinder.

4) Remove all spark plugs, and position the flywheel so that the roll pin in the end of the crankshaft is aligned vertically. Then look in each spark plug hole (looking away from the manifold side of the engine) to be sure that two of the pistons are at the top of their travel, and that the other two pistons are out of view. Then rotate the flywheel 180 degrees, and check that the other two pistons are at the top of their strokes, and the other two are now out of view. This check will confirm that the crank shaft is intact.

5) If the above checks appear normal, reinstall the spark plugs and try to start the engine, being sure that the reversing gear is in neutral.

6) If the engine sounds normal on cranking, but simply won't start, perform the following steps:

a. Compression: Repeat your compression test if any doubt exists as to normal compression during performance of the above diagnostics.

b. Ignition: Remove the coil lead from the center of the distributor cap and hold it approximately 1/4" from the head to confirm generation of a good spark. Then set the first cylinder (at the flywheel end) to TDC to confirm that the spark is created at the proper time.

NOTE: The TDC position of the No. 1 cylinder is most easily found by holding a finger over the spark plug hole in the first cylinder, while manually turning the flywheel counterclockwise. As soon as compression is felt, stop turning and look at the position of the roll pin in front of the crankshaft. Continue turning until the roll pin is perfectly vertical. The piston will then be at TDC.

c. Fuel: Remove the flame arrestor and housing to inspect the carburetor intake throat for the presence of raw fuel. If the fuel system is performing relatively normally, there should be raw fuel pooling in the carburetor throat after 15 to 20 seconds of accumulative cranking of the starter with the choke closed.

7) If the engine starts and sounds normal in neutral, try to engage forward while listening for any unusual noise to appear.

Good luck,

Don
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  #3   IP: 64.12.116.66
Old 12-12-2004, 08:37 PM
sundowner
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Problem diagnosed: Now it's on to reconstruction

I pulled the engine and removed transmission cover so as to be able to look at camshaft gear and timing gear. They seem fine.

Then I removed the flywheel and then the flywheel cover. So then I could look into the crankcase. Rotating flywheel end I could see that the weight on the other end of the crank did not initially rotate, but finally did.

So my crankshaft is broken.

I'll pull the block Monday.

As I remember it, the block is pinned in place to the top half of the transmission housing, and also pinned in place to the crankcase. So I can't just slide the block in the direction of the fly wheel. I have to loosen the transmission housing so the flywheen end can be lifted. Is that correct? Or do I have to totally separate the transmission housing from the crankcase?
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  #4   IP: 204.157.20.43
Old 12-13-2004, 10:12 AM
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Sundowner,

If you intend to only replace the crankshaft, you can lay the engine on its side, remove the lower 3 bolts from the thrust bearing and oil seal rings, and loosen the upper 3 bolts. Loosening these castings in this manner will allow you to move the oil pan down and away from the flywheel end, and away from the block.

If you discover that you need to remove and replace any of the rods, you can even remove and reinstall the pistons from below.

If you decide to disassemble the entire engine, you might want to refer to the second half of our service and overhaul manual for a step by step set of instructions.

Best regards,

Don Moyer
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  #5   IP: 64.12.116.134
Old 12-16-2004, 03:59 PM
sundowner
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I'm preparing for crankshaft

Don,
The break in the crankshaft was amazingly "smooth." Part of the surface was gray and likesand--like the surface between two pieces of shale. That was maybe 2/3 of the surface. The rest looked like a shear failure of the metal. (Is it forged steel? cast steel? cast iron?) That part of the brake was bright and shiny. I assume there was a fracture waiting for the right time to happen.

Anyway, your crankshaft and bearing will be here soon and I am cleaning up things.

I'm appalled at the rust scale stuck in the holes that connect the cylinder head and the block. Is this rust because the engine has water in after it just shuts off.

Is there anyway the water can be blown out between operations? Anything else I could do. I'm trying to sell the boat, so I don't want to do a lot, but I would like to do what I can.
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  #6   IP: 204.157.20.43
Old 12-17-2004, 02:40 PM
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The crank in the Atomic 4 was forged.

The shiny part of a fracture surface is the fatigue zone that pre-existed the ultimate failure of the crank. The surface in the fatigue zone is shiny because the two surfaces had the opportunity to rub together for quite some time (perhaps years) before the rest of the cross-section of the crank failed.

The shiny part of the fracture zone is typically perpendicular to the longitudinal axis of the member, while the part that is not shiny (but granular) is usually angular.

You may have heard it said that the Atomic 4 is prone to crankshaft failures because there is no center main bearing. Universal always claimed that the crank was over-designed to accommodate the load imposed by the lack of a center main, to the point that the reported failure rate was well below what one would expect, simply from random manufacturing defects that occur in any engine.

One of the strongest evidences of this claimed over-design of the crankshaft is the fact that a fatigue failure can exist (the shiny part) that extends half way across the cross-section of the crank before it will finally fail. In machinery that doesn't have the luxury of the additional weight that over-design usually requires (like the aircraft industry), things like a crankshaft are prone to fail when a fatigue crack develops which extends only of a fraction of the way into the cross-section of a structural member.

With regard to flushing out the cooling passages, you're better off to wait until the engine is back together, and then to pressure flush the block, head, and manifold.

Best regards,

Don
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  #7   IP: 64.12.116.134
Old 12-17-2004, 05:31 PM
sundowner
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Pressure Washing

Pressure washing after reassembly is the greatest suggestion. I would welcome suggestions for that.

How about this? First, after reinstalling bearings and crankshaft and mounting block on crankcase, but before installing head, clean out scale in head so nothing will be loose in the head that might replug holes between block and head.

Then poke loose the chips sticking up through the elongated holes and round holes in block. I'd assume these chips will drop down around the outside of the cylinders. Then install and torque the head.

Now what I would like to do is remove the side plate water jacket cover and pour water down into the recess for the thermostat and have the rust flow out the side. But that would mean leaving the thermostat cover off and not being able to torque two of the head bolts that hold on the thermostat cover.

Or can I torque those two bolts with washers in place to take up the space left by the omitted thermostat cover? Then flush, then remove washers and retorque with thermostat and cover in place?

Alternative: You tell me what do do.

Thanks for your explanation re: crankshaft fracture. It's actually very interesting.
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  #8   IP: 204.157.20.43
Old 12-18-2004, 09:37 AM
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Russ,

Here is the procedure for acid flushing and pressure flushing as taken from our FAQ and service and overhaul manual:

ACID FLUSHING: The following acid flush is most effective when used as a preventative maintenance measure every 3 to 5 years:

CAUTION: Be sure to wear proper protective clothing (including eye protection). Always add acid to water when mixing, and if possible, hang a bucket over the exhaust outlet to catch acid solution when discharging from boat.

1) Mix 1/3 gallon of household muriatic acid (30% concentration) into a 5 gallon bucket of water.

2) Draw the entire 5 gallons of acid solution into the engine through an inlet "T" fitting between the raw water through-hull and the inlet to the raw water cooling pump (the same "T" as used for winterizing the engine). For best results, thermostat should be removed and the by-pass hose temporarily clamped off. All the acid solution will then be pumped through the block by running the engine. Stop the engine as soon as the bucket is empty.

NOTE: Some of the acid solution will find its way into the exhaust system, which might loosen up any crud that may have built up within the water lift muffler and connecting plumbing.

3) Start the engine after letting the acid sit in the water jackets for about 15 minutes and run it long enough to thoroughly flush out the acid.

4) If it has been possible to retrieve the acid solution from the back of the exhaust system, add approximately 1/2 pound of household baking soda to five gallons of acid solution prior to discarding.

PRESSURE FLUSHING (PRELIMINARY STEPS):

1) Remove starter and alternator.

2) Remove the three 1/8" pipe-threaded water jacket drain plugs. Two of these plugs are in the block (one is located at the forward end of the block beside the starter, and the other is located beside the distributor base). The third plug is in the lower rear corner of the manifold.

NOTE: If the cooling system has not been serviced in many years, the plugs may have to be drilled out. If, after drilling out the plugs, the threads cannot be cleaned up with a 1/8" pipe tap, the drain hole(s) can be drilled out to 7/16" and threaded using a 1/4" pipe tap. Pipe taps and replacement 1/4" brass pipe plugs are available at most hardware stores.

3) Probe into each drain with a coat-hanger-sized wire to insure that it is open. If the drain on the manifold is clogged, it will be virtually impossible to open it without removing the freeze-out plug nearest the drain and probing the drain from inside the cooling jacket. While the drain in the manifold is not used to inject pressure water, as in the case of the drains in the block, it is still preferable to open the drain if at all possible.

FLUSHING THE BLOCK:

1) Install a 1/8" pipe-threaded 6" long brass nipple in one of the drain holes in the block and a 1/8" hex-headed brass pipe plug in the other block drain.

2) On early model engines, use a 1/8" brass 45 degree street-el (provided in kit) to facilitate reaching the drain hole behind the distributor.

NOTE 2: On late model engines, the 6" nipple can be left installed in the aft block drain after the flushing operation is complete to facilitate draining the block for winterizing or other servicing (use a 1/8" brass cap to close the end of the nipple). On early model engines, there is insufficient space for the nipple after the alternator is reinstalled; however, the 45 degree elbow can be left in place with a 1/8" hex-headed pipe plug installed to make subsequent draining somewhat easier.

NOTE 3: Early model engines have a cast iron crossover tube between the head and manifold which makes it difficult to flush the block and head separately from the manifold. In some cases, this cast crossover tube has been replaced with a rubber hose and 90 degree fittings. If this is the case on your engine, you may be able to install a discharge hose on the fitting on the head to be run overboard. You can then proceed with the following steps as in the case of a late model engine.

Steps 3 through 7 apply only to late model engines.

3) Remove the thermostat housing, both fittings, and the thermostat.

4) Install a 3/8" brass street-el in the outlet of the thermostat housing (the side marked "MAN"), and a 3/8" pipe plug in the inlet (the side marked "WP").

5) Reinstall the thermostat housing, but leave the thermostat out until after flushing is complete.

7) Install bushings on the end of the 6" nipple in the aft block drain as necessary so as to be able to install a swivel type garden hose fitting. It's also very convenient to install a small ball valve before the garden hose fitting so that you can stop/start the pressure from the hose for more aggressive flushing.

8) Flush the block until the effluent from the discharge hose is clear.

9) Move the 6" nipple to the other block drain, and flush that end of the block until the effluent of the discharge hose is clear.

FLUSHING THE MANIFOLD:

1) Remove the 1/2" fitting at the rear discharge of the manifold. Inspect and clean the 1/2" pipe thread opening as necessary.

2) Connect a garden hose to the rear outlet of the manifold for overboard discharge. A 1/2" male pipe thread by 3/4" male garden hose fitting is ideal for this purpose.

3) Install a second garden hose fitting to the front (inlet) of the manifold. Connect a garden hose to this fitting, and flush the manifold with as much water pressure as possible. As in the case of the block, it's a good idea to install a ball valve between the garden hose fitting and the manifold to enable you to stop/start the pressure from the hose.

4) When flushing is complete, remove garden hoses and all flushing fittings. Reinstall the thermostat, and reassemble the rest of the cooling system.

Best regards,

Don
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