bullflex couplings for prop shafts

[fran uteg]

I am picking up a pre-owned (69 total hours) 2011 Ranger 21EC and have a question about prop shaft alignment. Has the Ranger factory ever equipped a tug with a Vetus Bullflex coupler or do you know if any owners have done so as an aftrermarket add-on. I have had vibration problems on an antique launch equipped with a Yanmar 2GM20 and a #2 Bullflex coupler satisfactorily eliminated the problem. Fran Uteg

 

[Andrew Custis]

We have never used anything other than the standard shaft packing. A proper engine alignment should be done to make sure everything is ok on the boat but our vessels only use a 3-4' shaft which is very short. The 30hp will vibrate at idle (nature of a 3 cylinder diesel) but it should be very smooth under way at higher RPM.

 

[baz]

Fran:

Here's my info for prop shaft alignment... taken from a posting of mine here... http://www.tugnuts.com/viewtopic.php?f=5&t=1319&p=9339&hilit=alignment#p9339

Here's another tip I obtained from Bobby Kilker the other day. It was related to 'shaft alignment'.

Shaft alignment is the alignment of the engine's output shaft from the gearbox to the prop shaft. Too much mis-alignment means unwanted stress on the gearbox output shaft's bearing. Proper alignment is therefore crucial to avoid premature bearing failure. The alignment, if needed, requires the 4 engine mounts to be adjusted. Bobby indicated he has come to expect Ranger Tugs to have no issues with alignment as the Ranger Tug factory assembly folks do a great job.

To quickly determine if the shaft alignment is in need of adjustment one simply reaches down to the prop shaft (the shiny piece of shaft between the gearbox output and the stuffing box) and grab it and turn it with throttle lever in neutral position. If it turns freely the alignment is typically in good shape. However, if it's hard or stiff to turn or worse still one has to use a wrench to turn the shaft the alignment is in need of adjustment.

BTW -- the gearbox ratio for the R25's 4BY2-150 is 2.04:1 meaning that for just over two revolutions of the engine the prop shaft is rotated once. Thus, I'm presuming with the engine turning 4000 RPM the prop is rotating about 1960 RPM.