My new jackhammer

[odaydokay]

So we are cruising along under power (Universal M12) and all of a sudden we get this jackhammer sound from the engine. At first I thought we were throwing a rod or something, but rpm and temps were all unaffected.

I opened a hatch and it sounded like the sound was exhaust related. I took a damp rag so I could touch the black pipe (wrapped) exhaust. By applying force to the pipe, I could actually stop the noise. When we got to the dock I found a tiny bit of play between first nipple and flange, but that was not the jackhammer sound.

When I held the flange with one hand to take the play out and then hit the pipe with my other hand, I got the jackhammer noise as secondary vibration. Could both hear and feel something broken off or loose. No evidence of break in pipe, Y coupling or header flange, at least not external. No exhaust water leakage anywhere.

Anyone got a hunch on this?

 

[fred1diver]

never use a jackhammer as a boat engine
all kidding aside, what kind of engine do you have?
did the sound change with different engine speed?
if so it could be the crank shaft, rod, broken valve... hard to say without seeing the motor

 

[Ross]

Just keep looking. Check it in gear and in neutral, forward and reverse. You can make it stop so you should be able to isolate it.

 

[Stu Jackson]

Hope you can find the issue. The internet is not an appropriate place to diagnose sounds, smells, tastes, or electrical issues with pictures but no wiring diagrams.

 

[kloudie1]

Sounds like something that would be normally isolated by the elastic engine mounts .. that is hitting the hull or motor mounts.. Check the mounts themselves to see if they are bottoming out.. Sounds like when you are pushing/pulling, you may be lifting the mount enough to stoop the contact.

 

[Bill Roosa]

yea, sounds like you blew an engine mount.

 

[RAD]

The noise could be the shaft banging against the shaft log if you blew a mount, when I bought my Oday and while underway there was a loud knocking/banging noise and I thought it was something in the tranny....turns out to be a few bad engine mounts and mis alignment

 

[odaydokay]

Does not do it under. 3.5 knots, only as rpms come up. I can make the sound with engine shut off by banging on the black pipe exhaust. Sounds like it is in the exhaust manifold. Not an engine mount if I can make the sound with engine off right?

 

[woodster]

might wana check the damper plate on the flywheel while you are checking....just my 2 cents...

regards

woody

 

[Ray Bowles]

A blown exhaust gasket at the header/head flange can cause a noise very simular to what you are speaking about. A second item can be a spring located flange joint. Many industrial motors had a header mounted to the head of the motor and a spring assembly that held the next exhaust pipe section onto and over the header pipe. This type of mount could also make such noise.
Ray

 

[jeanharvey]

So we are cruising along under power (Universal M12) and all of a sudden we get this jackhammer sound from the engine. At first I thought we were throwing a rod or something, but rpm and temps were all unaffected.

I opened a hatch and it sounded like the sound was exhaust related. I took a damp rag so I could touch the black pipe (wrapped) exhaust. By applying force to the pipe, I could actually stop the noise. When we got to the dock I found a tiny bit of play between first nipple and flange, but that was not the jackhammer sound.

When I held the flange with one hand to take the play out and then hit the pipe with my other hand, I got the jackhammer noise as secondary vibration. Could both hear and feel something broken off or loose. No evidence of break in pipe, Y coupling or header flange, at least not external. No exhaust water leakage anywhere.

Anyone got a hunch on this?

I would start by checking the exhaust leaks gasket (between engine and exhaust manifold and exhaust manifold to exhaust pipe). pass your hand close to the pipe or engine (I don't have to tell you try not to touch it but you could check it when engine cold. Any leak from the exhaust before the muffler would make a louder sound. If the exhaust gasket is leaking or damage. If you have hanger bracket,make sure the bracket are tight. If the hanger bracket are to loose or broken the weight will be on the exhaust manifold.
Jean Harvey

 

[rblack27]

exhaust banging

So we are cruising along under power (Universal M12) and all of a sudden we get this jackhammer sound from the engine. At first I thought we were throwing a rod or something, but rpm and temps were all unaffected.

I opened a hatch and it sounded like the sound was exhaust related. I took a damp rag so I could touch the black pipe (wrapped) exhaust. By applying force to the pipe, I could actually stop the noise. When we got to the dock I found a tiny bit of play between first nipple and flange, but that was not the jackhammer sound.

When I held the flange with one hand to take the play out and then hit the pipe with my other hand, I got the jackhammer noise as secondary vibration. Could both hear and feel something broken off or loose. No evidence of break in pipe, Y coupling or header flange, at least not external. No exhaust water leakage anywhere.

Anyone got a hunch on this?

This may be too obvious, but in my boat there is a 1'-2' length of flat iron run from the engine to the top part of the black-iron exhaust riser for stability /support. Many years ago one end of this cracked and broke at the attachment point for the exhaust, after which the remaining flat iron would bang against the exhaust pipe whenever the engine was running. Since the broken end was up in the dark area near the top of the engine compartment, and it still looked "attached" when the engine was not running, it was not readily visible. Sounds a lot like what you are describing.

At the end of the day, black iron pipe and the fidgety diesel don't go together that well over the long run

Btw, I'd suggest keeping a CO monitor handy any time there is a suspicion of an exhaust system problem.


rb

 

[eherlihy]

This could also be play in the exhaust system.

Occasionally, at the right RPM, the vent hose on my exhaust vented loop will slap against the underside of the cockpit. The slap is amplified by the cockpit floor, and it is very disconcerting. A simple tug on the hose provides a little tension on the hose as it goes through a tie wrap, and the noise stops. Another fix would be to put foam on the hose, but I don't bother.

I would check the exhaust elbow (for cracks) and then look closely at the vented loop.

 

[odaydokay]

This may be too obvious, but in my boat there is a 1'-2' length of flat iron run from the engine to the top part of the black-iron exhaust riser for stability /support. Many years ago one end of this cracked and broke at the attachment point for the exhaust, after which the remaining flat iron would bang against the exhaust pipe whenever the engine was running. Since the broken end was up in the dark area near the top of the engine compartment, and it still looked "attached" when the engine was not running, it was not readily visible. Sounds a lot like what you are describing.

At the end of the day, black iron pipe and the fidgety diesel don't go together that well over the long run

Btw, I'd suggest keeping a CO monitor handy any time there is a suspicion of an exhaust system problem.


rb

This may be too obvious, but in my boat there is a 1'-2' length of flat iron run from the engine to the top part of the black-iron exhaust riser for stability /support. Many years ago one end of this cracked . That is exactly how it sounds, but I do not believe there is such a thing in my set up. I am going to do some more looking tomorrow, however.

 

[2taylorscotts]

Universal jackhammer finder

I'd suggest investing in a mechanics stethoscope. I used one in my work for twenty some years and have one in my tool box now. I think I paid about $8.00 for it and it's money well-spent for locating the source of squeaks, squeals, knocks and bangs--especially when there is a lot of other noise going on. It's a typical stethoscope with a plastic mushroom at the end, housing a metal diaphragm with a probe about eight inches long. With the engine knocking carefully touch the probe to all the suspected sources. I emphasize "CAREFULLY" because a sharp rap on something solid,or Neptune forbid, a touch to a running alternator fan can give you a memorable headache. I've used one on everything from a monster air handling unit to my wife's vacuum cleaner.
I have the same Universal in my O'Day 272. My knock was the alternator vibrating against the engine compartment wall--solved by a new belt 1/2" shorter.
Best of luck.

S/V Spirit
Barnum Bay, WI

So we are cruising along under power (Universal M12) and all of a sudden we get this jackhammer sound from the engine. At first I thought we were throwing a rod or something, but rpm and temps were all unaffected.

I opened a hatch and it sounded like the sound was exhaust related. I took a damp rag so I could touch the black pipe (wrapped) exhaust. By applying force to the pipe, I could actually stop the noise. When we got to the dock I found a tiny bit of play between first nipple and flange, but that was not the jackhammer sound.

When I held the flange with one hand to take the play out and then hit the pipe with my other hand, I got the jackhammer noise as secondary vibration. Could both hear and feel something broken off or loose. No evidence of break in pipe, Y coupling or header flange, at least not external. No exhaust water leakage anywhere.

Anyone got a hunch on this?

 

[tailwind]

The noise might be caused by a miss due to air in the injector lines. Try bleeding the filter and injector lines.

 

[Weasel]

Check your mixer elbow before the muffler. You could have a hole in the unit if it is steel or cast iron .

 

[odaydokay]

Thanks to all of you for weighing in. This morning I was able to isolate the problem. As noted, the pounding sends sound throughout the whole damn boat so more exploration was needed. The sound can now be replicated with the engine off. Grabbing the prop shaft (neutral) and spinning it vigorously back and forth creates a hammering noice with 3-4 ricochets to it about 3-4 feet aft of where the stuffing box is located, that is to say outside the boat. There is some play in the shaft as well, though not a lot, but pushing and pulling it laterally creates the noise as well. Hard to believe a shaft anode slipped. Something caught on the prop? A bearing?

 

[sailnoproblem]

Not sure but!

Not sure, but if you can stop the noise by holding the exhaust pipe I doubt it's internal. Check everything exhaust related. Good Luck.

 

[kloudie1]

Sounds like time for a dive to investigate.