bent shaft?

[Marty Levenson]

I have a slight wobble and vibration visible at the stuffing box when the engine is running in gear. I believe the alignment is good. The prop is clean. With the output coupling unbolted, if I rotate the prop shaft by hand I cannot see or feel any fluctuation or movement at that end.

Still unbolted, rotating the shaft by hand, with my finger touching both the output coupling and the shaft coupling I cannot sense any wobble.

So, are a bent shaft or worn cutlass bearing the only possibilities? I have a haulout booked for Monday and want to be sure I am not wasting my money/time. any further tests I can do?

Many thanks,
Marty

[67c&ccorv]

Can you grab the shaft near the cutlass bearing and give it a shake to see if there is any play in there?

If there is you probably have a worn cutlass bearing.

[Al Schober]

As I recall, the T27 has only the bearing just forward of the prop - no steady bearing. Please correct me if I'm wrong.
What you need is a dial indicator. Lacking that, you need a better measure of the runout in your shafting. Just rotate the shaft by hand (in neutral) and watch the change in clearance to something fixed about half way to the bearing (piece of wood held by a c-clamp?). See how much the clearance changes as the shaft rotates. If it just touches in one position, and then 180 deg out the clearance is less than a piece of cardboard, you should be OK.
Of course, this says nothing about what the prop is doing. The shaft can be straight inboard and have a kink at the aft end which will really throw off the propeller - which will really shake the boat.
Personally, if it's not shaking the boat, I'd live with it. A slight wobble of the shaft & stuffing box isn't a big deal in my book.

[hanleyclifford]

Marty - Since you have a haul out scheduled here is a suggestion. Remove the shaft and prop out the back but leave the shaft coupling with the engine. Go to the hardware store and buy a cheap chrome plated brass shower pole which is very light, and run it in thru the cutlass and up to the engine. Because they are light and easy to adjust you will be able to see if the cutlass is true to the output coupling. Your engine may be too high or too low on the mounts. It is actually possible to get a "good" alignment with such an out of true engine/cutlass relationship but because of the weight of a shaft this can be difficult to detect.

[Marty Levenson]

Thank you for your replies....very useful in steering me toward a decision on how to proceed.

I have a newly rebuilt engine, a brand new exhaust system and riser, and rewired dc distribution panel (Blue Sea!). Having a wobble in the aft part of the shaft makes me want to complete the job: shaft out (straighten or replace) stuffing box completely redone, new cutlass bearing. The only remaining part of the system is the gas tank, which as its the original high nickel monel metal, don't plan on ever changing.

Amazing how just DECIDING changes my feeling about the work: now looking forward to it while a couple days ago I felt unsure and annoyed about the whole thing. Also helped talking to a good mechanic working close to the travel lift (Skookum Yachts on Granville Island, Vancouver) who praised Atomic Fours, loves the good old boats, and offered me free tools and consultation. They were amazed I had repowered on my own and "like to work with handy owners".

Marty