Metal shavings inside water jacket

[SoCal Sailor]

Hello everyone,

A few weeks ago I was coming into my slip and sometimes I need to go in reverse at the last moment to “walk” the stern around. This time I accidentally pushed the throttle lever wide open while holding back on the shifter lever. She ran at high rpm for maybe 1-2 seconds before I backed off the throttle. Immediately after I started to hear a “ping ping pa pa ping pinging” sound. Not sure what it was at the time thought maybe it was in the gearbox. The next day I started it back up and noticed that the pinging was louder when it was cold and I still had forward and reverse. The engine sounded rough with an extra vibration so, after reading a few good threads, I went ahead and checked compression. I got 120 - 0 - 120 - 30 from back to front (flywheel is front). Thought maybe it’s a broken valve, so I decided it’s time to remove the head.

20 hrs later head is removed; it’s not a valve, I have a broken piston. So I guess my first question is “what is the cause”? “And is the block too corroded for a major overhaul“?

Also look what I found in the water jacket... it’s looks like metal shavings!

Anyway, I have the engine ready to be removed from the boat. I’m taking the block to a machine shop to have it inspected and cleaned. I’m hoping it’s still in good condition so I can perform the major overhaul. Any advice from this point is much appreciated!

“Sojourn”
1974 Cal 2-27

[JOHN COOKSON]

Bummer to hear about the destroyed piston.
Our host, MMI, sells rebuilt A4s in various stages of completion. Have you checked this option out? I don't know your ability, resources, time, and $. In your situation a MMI rebuild would be the best option? Just an idea - I'm not promoting particular course of action.

ex TRUE GRIT

[Mo]

Humm...that piston looks like it got cleaned...as if water hit it. I wouldn't be able to say if it was before or after it broke? I might be wrong as well, but that piston is cleaner than the other. ? the cause water in the top end when it went to high rpm. Something would have to give if water got in the top end when it was doing high rpm...might have been why the piston broke. Another thought, did the broken piston break the block and I wonder what kind of shape the cyl bore is in. Either way, I truly hope that is not the case.

Pistons break up through like that when the engine gets loose as well...just plain failure at the pin boss when the connecting rod is connected. Actually, the more I look at it that looks like the case. When I initially looked at it I thought I saw 3 cracks so I was thinking a compression impact or something off there...yours is straight across so at the connecting rod was probable source. In retrospect, I think you cleaned it off for us to see. Correct me if I'm wrong.

Have a look at top right near the water jacket. Is that a crack or debris sitting on the head.

Sorry to hear of your troubles.

[SoCal Sailor]

Thank you for your replies!

Mo, The broken piston was noticeably cleaner than the rest. I didn’t clean it any more than the rest. I just used a shop vac to suck up all the loose debris left over from the head. I think your right about water in the cylinder being the culprit. Could that be from a poor seal?

I’m considering getting a rebuilt block from MMI. The solenoid casing broke when I was removing the starter motor. Didn’t take a lot of force to do it either.

So how much of a MMI rebuilt A4 would be ideal to replace? Does the gears and water pump need to be replaced? I just bought a new water pump last year. The head and manifold just came back from the machine shop, they look new. I have the head, manifold, valve cover, and water jacket gaskets. Maybe I should take these questions to MMi direct.

I have the engine out and ready to be dropped off at the machine shop but maybe it’s not even worth the money for sandblasting.

[JOHN COOKSON]

T
So how much of a MMI rebuilt A4 would be ideal to replace? Does the gears and water pump need to be replaced? I just bought a new water pump last year. The head and manifold just came back from the machine shop, they look new. I have the head, manifold, valve cover, and water jacket gaskets. Maybe I should take these questions to MMi direct.
.

Yes.
Call Ken @ MMI parts sales.

ex TRUE GRIT

[Mo]

Thank you for your replies!

Mo, The broken piston was noticeably cleaner than the rest. I didn’t clean it any more than the rest. I just used a shop vac to suck up all the loose debris left over from the head. I think your right about water in the cylinder being the culprit. Could that be from a poor seal?

I’m considering getting a rebuilt block from MMI. The solenoid casing broke when I was removing the starter motor. Didn’t take a lot of force to do it either.

So how much of a MMI rebuilt A4 would be ideal to replace? Does the gears and water pump need to be replaced? I just bought a new water pump last year. The head and manifold just came back from the machine shop, they look new. I have the head, manifold, valve cover, and water jacket gaskets. Maybe I should take these questions to MMi direct.

I have the engine out and ready to be dropped off at the machine shop but maybe it’s not even worth the money for sandblasting.

As John said, you should talk to Ken. Your reversing gear should be salvageable, the water pump would be fine, the starter can be replaced. Many parts on the engine would still likely be fine.

Yeah, she just came apart. It can happen. There might have been a bit water, not sure. You said you ran it following the incident so it ran on 3 cyl and likely scored up the bore. The block might have been compromised, maybe even in the bore to allow some water that would have made it look cleaner. That might have cleaned the piston top and area on your second running...hard to say.

Either way, I think you should be looking for an engine. You might get into that for $1000 to $1500 for a shop to take a look, and still be where you are right now. As John suggested, you should talk to Ken and see what he thinks. Shavings in the water jacket...I'm thinking the bore is torn up an even may be perforated. You will have a multitude of good parts there. reversing gear should be OK, water pump, exhaust manifold, carb...all that stuff should be fine. Starters are easy to come by.

Let us know how you make out.

[ndutton]

Good to hear you're considering MMI rebuild options. If the broken piston was due to water incursion, a hydraulic event, there's every chance the connecting rod is damaged and the no-center-main-bearing crankshaft is bent. If your block is salvageable I expect it would need deep and expensive repairs to bring it back to life.