Packing box "wobbling" at low RPMs

[Fastjeff]

Got the same problem on mine, and a theory: Unless one has the flange mounted to the prop shaft and turned in a lathe (as a unit) the flange can run out--and even with a perfect prop shaft. If this is the case, the usual method of aligning the prop shaft is meaningless!

Grrr!

Here's what I'm gonna try (when the boat is in the water): Using a 1/2 inch drill with a pulley clamped in the jaws, I'm going to rotate the prop shaft with a section of rope (or TBD). When--and not if--the little b*st*rd runs out, I'm gonna shim the coupling faces with brass shim stock until it doesn't (clamping the shims in with the bolts).

I'll report back on how this works.

Jeff

[Maestro]

Another factor to add to the mystery - I know my transmission is wearing out.

The shaft turns very slowly even when in neutral. I have adjusted the linkage many times with no effect. According to the manual the problem is most likely worn clutch plates.

Not sure if a transmission problem such as that could cause our "wobbling" problem.

Getting the transmission rebuilt is on the long term checklist...right now the shaft turning in neutral problem is very slight.

[Roger2]

Maestro,
I don't see the shaft turning slowly as a problem. The friction of oil between the clutch plates will cause this, and it most likely will continue after rebuild. Worn clutch plates will cause slippage while in gear, not the turning in neutral. I would say that the trans is not the problem, "unless you can take shaft and move it up & down."

my 2 cents
Roger

[Maestro]

Roger...thanks for your insight. Much appreciated.

I have never noticed the transmission slip while in gear - so that's good.

When I remove the coupling bolts, the prop shaft flange rests a tiny bit lower than the transmission flange. Not sure if this means I have an alignment problem.

[Roger2]

Maestro,
The weight of shaft will cause it to drop when unbolted. To check alignment pull coupling to gather, slightly loosen bolts, and check with a feeler gauge, at all 4 positions, top, Bottom, left and right sides, Turn coupling 90 degrees, and repeat measurements. Do this 4 times, or all the way around. If you chart these positions, and have a bent shaft, you will see a larger measurement go all the way around.
Chart: Top , Bot, Left, Right
0
90
180
270

Hope this helps

Roger

[Fastjeff]

Note that this well accepted procedure is correct ONLY if the face of the shaft coupling is not running out. Unfortunately no way to dial indicate that in place...

The flange face of my port shaft definitely was running out (the coupling is pressed on the shaft) and had to be faced off in a lathe. The starboard shaft--that has a wobble in it--was NOT treated to Mr. Lathe and probably has some run out in the flange face.

I'll soon be doing a little in-water research (spinning the shaft with a 1/2 inch drill, with the coupling bolts loosened) to see if that's the case. Should be interesting.

Jeff

[Roger2]

The feeler gauge procedure will tell you that either coupling face, or the shaft is bent. you then have to go to the lathe to find out which and correct.

Roger

[Fastjeff]

And that's the problem! Just remove the coupling from the shaft (a royal PITA), then the prop, and yank the shaft out and take it to a machine shop...etc.

Too bad there's not some reliable way of dial indicating the flange face IN PLACE. I've wracked my miniscule brain trying to come up with a way to no event.

Jeff

[barkleydave]

Perfection is not a reality. There are just too many factors that effect trueness of the drive line. Prop, Strut alignment, Cutless bearing wear, Coupler, Engine mount wear, Alignment, and yes hull flex! On and On. If you align the shaft and wobble is minimal and the boat is running smooth without excess vibration.... leave it be and enjoy your big M.

safe boating,
dave

[Fastjeff]

Good advice, but I'm anal, see, so...

Jeff