I thought I would put this out to see if others have experienced the same. I have a Universal M18 in my '88 Catalina (490 hours). A few weeks ago I tightened down on my packing gland nut to limit the water flow. I also noted that a nut was missing on the rear right side of the engine mount. The nut holds the engine down on the mount unit itself. I added a new nut and tightened down. Under power this past weekend I noted a very stong cavitation or vibration when I went to 1500 RPM and higher. It was one of those harmonic rumblings, like flying on an old DC-3! I put the engine in neutral and revved it up and noted it was not the engine. No leakage anywhere. The big question is: could I have set off the shaft alignment by adding the mount nut and tightening down on that side of the engine? Could a few turns on the packing gland nut cause a shaft alignment problem? Is this symptimatic of a bad cutlass bearing? I have yet to dive down to see if I have anything hanging up on the prop, zinc or cutlass bearing. Thanks Bob
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Sounds like alignment, check the other engine
mounts, but just "cranking" down on one corner would probably throw it out even if other mounts were OK. Overtightening packing gland may score the shaft but unless so grossly tight as to inhibit rotation shouldn't cause vibrations you describe.
mounts, but just "cranking" down on one corner would probably throw it out even if other mounts were OK. Overtightening packing gland may score the shaft but unless so grossly tight as to inhibit rotation shouldn't cause vibrations you describe.
B
Bob
Thanks Ted
Thanks Ted. I never messed much with shaft alignments on previous diesel powered engines. I did question just why the nut was missing? I first thought it was negligence on the prior owners part, but the more I think of it the more I realize that adding the nut and torqueing down could very well set off the alignment just so to cause the vibration. The first thing I will do is take the nut off and see of that helps. Bob
Thanks Ted. I never messed much with shaft alignments on previous diesel powered engines. I did question just why the nut was missing? I first thought it was negligence on the prior owners part, but the more I think of it the more I realize that adding the nut and torqueing down could very well set off the alignment just so to cause the vibration. The first thing I will do is take the nut off and see of that helps. Bob
I'll try to attach a link here to a previous
discussion on this board. Mount nuts are notorious for vibrating loose, and alignment gets thrown off by factors as diverse as rig tune or just getting hauled and splashed again.
discussion on this board. Mount nuts are notorious for vibrating loose, and alignment gets thrown off by factors as diverse as rig tune or just getting hauled and splashed again.
E
ed
you got good advice here.
You have an alignment problem. thats probably why the nut came off in the first place. just go ahead and re-align it and you probably will be fine. Dont run it out of line or you could trash the cutlass bearing or rip loose the tube thru the hull and or bend the shaft.
You have an alignment problem. thats probably why the nut came off in the first place. just go ahead and re-align it and you probably will be fine. Dont run it out of line or you could trash the cutlass bearing or rip loose the tube thru the hull and or bend the shaft.
B
Bob
Great Ted
Great procedure! You know, I never considered the consequences of what tightening down on a mounting bolt could do. You would think the opposite; that the rubber in the mount would take any of the excess vibration without upsetting the shaft alignment. The engine afterall sounds great in neutral, so its almost a double edged sword! But, by torqueing down on all the mounting nuts I probably really set the alignment off. The harmonic vibration throughout the vessel that occurs over 1500 rpm, is similar to flying in an old DC-3!! What would I feel in the vessel if it were a worn cutlass bearing over the issue I have presently? Thanks Bob
Great procedure! You know, I never considered the consequences of what tightening down on a mounting bolt could do. You would think the opposite; that the rubber in the mount would take any of the excess vibration without upsetting the shaft alignment. The engine afterall sounds great in neutral, so its almost a double edged sword! But, by torqueing down on all the mounting nuts I probably really set the alignment off. The harmonic vibration throughout the vessel that occurs over 1500 rpm, is similar to flying in an old DC-3!! What would I feel in the vessel if it were a worn cutlass bearing over the issue I have presently? Thanks Bob
L
Landsend
easy check...
Try turning the prop shaft by hand. If it rotates easily the alignment isn't too bad.
Try turning the prop shaft by hand. If it rotates easily the alignment isn't too bad.
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