Yanmar - Vibration in gear at higher rpms

[Chuteman]

Background - 4JH4AE, 54 hp, 640 hrs, Flexofold prop

No problems to date, but after launching boat Monday - did not notice anything in short hop over to Greece. But this am at the end of an overnight that included at least 15 hrs of motoring (aargh), I noticed what I thought was a level of vibration that was not familiar.

Starts at about 2200 rpm and increases definitely noticeable at 2400. I pick up the vibration in my feet and on the stb side wheel. Only in gear, only tested forward. Did not dive on prop yet, as a nap was #1 on my list, but I'll check and see if I ran over a line last night - never saw or got close to any fishing gear.

Did not know if the experts and other Yanmar owners have some insights or ideas. BTW - a shaft alignment has not been done by me and don't think prior owner did either. Everything looked good on the hard, only changed anode at end of prop.
Thanks in advance

[Captain Bill]

My experience is that this happens when I get a small piece of line caught up in the prop. In the past year I have twice picked up a piece of line in water thousands of feet deep so I know I didn’t run over someone’s crab or fish trap. In both cases they were pieces of polypropylene line which of course floats. Unfortunately there's a lot of that floating around these days.

[Don L]

you did the most basic thing right, checked the gear oil level?

[terrylad]

Jump in, take a look! Have a sharp knife handy!

I picked up a sheet of black plastic ground cover in the Chesapeake once when the water was below 50degF. Borrowed a tree saw from a beach property and cut it out from the dinghy. Also, I picked up another sheet of ground cover in the ICW in S. Carolina and was able to cut it off underwater. That stuff shuts the engine right down, black smoke chuffing out of the exhaust. I've been snagged with lobster lines, anchor lines, fishing lines, and netting to contend with, but the big issue is "how cold is the water?"

[Chuteman]

Thanks for responses and personal experiences

After posting and waking up a little, I took a look although the visibility was not great and rough water, the prop and shaft look clear.

There is not a problem with power, chugging or even that bad when it goes to higher rpm, it just felt different this am. I 'll keep checking all the basics and check back for any new hints.

Thanks again

[Chuteman]

Transmission oil level - spot on

Water temp - not that cold but big difference vs air temp

Engine Mounts /Feet - I checked them after reply, right away I saw some black flakes next to the forward Stb one + it appears slightly turned, otherwise it looks and feels fine. The flakes were not there before Monday because the whole compartment was cleaned/swept

Alignment - think that is the next thing to check. it is on the List but has moved up with a bullet.
I'll study up before diving in

[cheoah]

Yep, I'd jump in first off and rule out prop. It happens to so many of us, I feel like I'm always under there but mostly for barnacles. Hopefully you're prop is just fouled, but you can check cutlass bearing and Flexofold while you're down there, although you did just have it on the hard.

Good luck-

[Cotemar]

Check you motor mounts with a wrench on each bolt.
Had the same problem

[Chuteman]

Thanks for add'l responses and suggestions

Prop - took another look in much clearer water, clean = no lines, trash, anything.
Cutlass -everything looked and felt ok ( untrained comment ) before launch Monday

Cotemar - I interpret your comment to test each mount before starting alignment? Ok, will do.

[Cheechako]

sounds a bit like a worn cutlass.... but I'd align first.

[Tonys tank]

If you don't have self bleeding prop shaft seals, did you purge when re-launched?.


The cutless bearings could be running dry

Tony 777

[Cheechako]

Originally Posted by Tonys tank

If you don't have self bleeding prop shaft seals, did you purge when re-launched?.


The cutless bearings could be running dry

Tony 777

Never heard of this... you mean on non conventional shaft seals..? Please elaborate.

[sv Shearwater]

I would think he does means a conventional shaft seal. Not a stuffing box. A conventional shaft seal without a vent line traps air in the stern tube after launch and prevents water from lubricating the seal. The result can be that the faces of the seal get hot and start to stick together and then start to chatter as they stick and unstick as the shaft rotates. The result can be a horrible racket and vibration that increases with rpm.