Rebuilt engine starts perfectly, then comes to screaching halt

[TheDude7B7]

Fellow Afourians-

Finally fired up my engine after a 3 year rebuild project (thank you COVID and other stressful life events). She started and ran flawlessly, idling smoothly at 850 rpm wth 40psi of oil pressure. Then, to my dismay, two minutes into the first run the engine came to a screaching halt. After the engine stopped, turning the crank resulted in a squeaking noise. Video links are below. After the engine cooled down, the squeaking went away. Engine started up perfectly again with the same result.

Has anyone heard this noise before? It's gotta be heat realated and I'm thinking it might be some oil startvation. It sounds like it's coming from behind the flywheel or the #1 cylinder.

As far as the rebuild, I had a machinist bore the cylinders 20 over, turn the main and rod journals. I also had him do the assembly with new pistons, rings, rod, main, cam bearings. Could this be due to a lack of end play? I'm stumped and really want to exhast all possibilities before I have to pull the engine again. ANy thoughts would be helpful.

Video of engine seizing:

https://youtube.com/shorts/PfYWaLNe4d4?feature=share

Video of turning crank:

https://youtube.com/shorts/xjDrVXxh-Rk?feature=share

[ndutton]

Please try it with the shaft coupler unbolted and pulled away from the engine.

[TheDude7B7]

Thanks Neil. Will try this on Saturday when I get back out there.

[joe_db]

Please try it with the shaft coupler unbolted and pulled away from the engine.

Great idea! I am failing to come up with a logical explanation for this being an internal issue.

[ndutton]

Will try this on Saturday when I get back out there.

Dude, any update??

[TheDude7B7]

Saturday didn't happen. Turns out I forgot about a previous engagement. Hoping to get out there this weekend.

[sastanley]

we look forward to it...other crap gets in the way a lot...for all of us..update when you can!

[Dave Neptune]

Was the 'ring gap" set and checked. It only takes a couple of minutes for "too little" gap to stop the engine when the ring gap goes away due to cylinder heat and that will bring the engine to a stop. Once cooled they can have enough clearance to turn freely. They can also make a scraping sound when tight.

Even the "proper pre-gapped rings" need to be checked.

The slow stop of the engine and being free when cooled lead me to this "possibility". Hopefully I'm wrong.

Did the engine turn freely before starting?

Dave Neptune

[TheDude7B7]

Was able to get out today to do some troubleshooting. Disconnecting the prop shaft did the trick. Ran the engine for an hour between idle and 2000 RPM with zero issues. Temp stayed at 180-190 and oil pressure was steady at low 30's at idle and 40 at speed. It ran better and cleaner than ever so I'm feeling a bit better about the rotating assemply now and the job the machinist did. Was pretty stoked to hear the little heart of my boat pumping away liek it was brand new.

Haven't had a chance to connect the prop shaft back up, but while running the engine, I noticed that even though the the revering gear was in neutral the tail shaft was still spinning at engine speed. I was able to stop it with my foot, but felt a good amount of vibration through it when I did. Almost similar to the vibration you feel with engaging reverse. I am able put the gear into to forward and reverse fairly easily by hand ut in neutral it seems like somthing is sticking a bit. Looking at the prop shaft, it appears to be aligned. The gap looks completely parallel and the shaft mates to the coupling easily.

I wont be able to get back out to the boat for another 2 weeks to try it with the prop shaft connected. But until then, any thoughts on the issue with the tail shaft always being a bit engaged? Could it be as simple as adjuging the forard gear engagement? Could the clutch plates be sticking? And could all that cause that god awful squeal and stopping of the engine after a few minutes of running initially with the shaft connected? Could the prop shaft be putting forward pressure on the crank and thus the forward main bearing causing it to heat and seize (if that is even possible)? To quote Gandalf.. "Questions, Questions that need answers" LOL.

[ndutton]

Thanks for doing that test, it really helps.

My bet is your stuffing box is adjusted too tight, simple as that. With the driveline attached, the rotating shaft heats up due to friction with the flax inside the gland, the shaft expands with the heat, the friction increases making more heat→more friction→more drag on the shaft until it reaches a point that the engine can no longer overcome the drag. That's the squeal you're hearing, the final protest from the shaft. Your boat is talking to you with that squeal.

Next test is to reattach the shaft coupler, loosen the stuffing box so it drips profusely with the engine off (don't worry, it's only a test and your auto bilge pump should be able to manage it easily) and then do another running test. I'll bet the problem disappears confirming what I'm suggesting. Once that is confirmed, replace the flax inside the stuffing box and adjust it as loose as possible so it drips under way but not at rest. A delicate touch is the way to go. It should be noted that worn out flax requires way too much tightness to stop the dripping. When was the last time you changed yours?

Finally, there is no neutral in the Atomic 4 reversing gear. There's forward with a detent clunk you can feel, there's reverse with no detent that you have to hold pressure on the shift lever to maintain and there's a sweet spot somewhere between the two where the shaft does not turn.

[TheDude7B7]

Thanks Neil. That will be the first thing I do when I get back on the boat. One thing I would add is in the initial video where the engine stalls out, forward wasn't completely engaged. I could stop the shaft by hand if I wanted to, so I'm not sure if the shaft bound up in the stuffing box, it would have stalled the engine, unless the fiction plates were putting enough pressure on the crank. Also, if it was the prop shaft seizing, any idea why the squeaking noise would be coming from the front of the engine and not back by the stuffing box?

[ndutton]

Dude, I'm guiding your testing based on my very similar experience to your shutdown description including the squeal (see links to pertinent posts below). This may turn out to be something different but if so, the testing will eliminate my hypothesis which is good information too. And by the way, this thread has reminded me it's time to replace my packing flax.

That said, I don't mean to discount your observation that the squeal came from the front of the engine but frankly when the engine is running it's hard to pinpoint the source of noises. Also, your successful test with the driveline disconnected points me to the driveline and away from anything going on at the front of the engine. Let's get the second test done (driveline reconnected, stuffing box adjusted loose) and see what it tells us before we start chasing other zephyrs.

Looking forward to your next report.

https://www.moyermarineforum.com/forums/showpost.php?p=24045&postcount=14

https://www.moyermarineforum.com/forums/showpost.php?p=57300&postcount=19

https://www.moyermarineforum.com/forums/showpost.php?p=69295&postcount=11

[TheDude7B7]

Hey Neil-

Reattached the shaft and decided to see if the problem would happen again before loosening the stuffing box. To my surprise the engine ran fine with zero protest. The stuffing box was dripping at the same rate it normally does while spinning. I was elated until I noticed quite a bit of wobble in the shaft by the stiffing box. Didn't feel too much vibration but it was definitely visible (see link below). While attaching the shaft, I went through the process of using feeler gauges to make sure it was aligned and all looked ok. Ran out of time and had to leave before I could double check the alignment. Only other thing I can think of is that the shaft got bent somehow during one of the many haul outs that have occurred aver the last few years while I was working on the engine, but that seems unlikely.

Thanks for all your diagnostic help on this matter. Given my limited time at this point in life, it has really helped speed things along.

Stuffing Box Wobble:

https://youtube.com/shorts/9eLDpo3QJpc?feature=share

[joe_db]

Hey Neil-

Reattached the shaft and decided to see if the problem would happen again before loosening the stuffing box. To my surprise the engine ran fine with zero protest. The stuffing box was dripping at the same rate it normally does while spinning. I was elated until I noticed quite a bit of wobble in the shaft by the stiffing box. Didn't feel too much vibration but it was definitely visible (see link below). While attaching the shaft, I went through the process of using feeler gauges to make sure it was aligned and all looked ok. Ran out of time and had to leave before I could double check the alignment. Only other thing I can think of is that the shaft got bent somehow during one of the many haul outs that have occurred aver the last few years while I was working on the engine, but that seems unlikely.

Thanks for all your diagnostic help on this matter. Given my limited time at this point in life, it has really helped speed things along.

Stuffing Box Wobble:
https://youtube.com/shorts/9eLDpo3QJpc?feature=share

Dive under the boat and grab the shaft. See if it can move in the cutless bearing. If it can, there is your issue. Also check to see if the engine mounts are all tight.

[TheDude7B7]

Yeah, diving under the boat in the Morris Canal in NJ is likely to make me grow another arm. LOL. I'll check the mounts though. I have to have the boat hauled anyway to clear out the intake and take care of a few other things. I can have them check the cutlass bearing while they are at it. I'll let you know what happens.