Seeking knowledgeable advice re replacing the shaft log, and associated drive train installations and alignment.
The patient is a 1986 Jonmeri 40. Using a cute custom-made tool crafted by a local machine shop (photo 1) after 2 days of effort, finally got the cutless bearing out and removed the prop shaft. This revealed extensive corrosion
at the in-board end of the shaft log tube, especially on the underside and under the retaining strap for the Volvo
dripless shaft seal
(photos 2&3). There are 1/8" diameter holes right through the stainless at the edge where the Volvo
seats. Lucky we didn't sink the boat
is on the hard
in Johor, Malaysia
. Given the policies, realities and work
force at this yard, this is going to be a DIY
job. The yard will not allow us to bring in any outside (i.e., qualified) labour. Before I start blindly grinding away I need a lot of information, a plan, and confidence.
Here are the relevant (and perhaps irrelevant) details I can offer (attempts to get info from the manufacturer in Finland
are in process, but so far frustrating):
The existing tube appears to be 50mm ID and 54mm OD, length approx. 30cm on top and 14cm on the bottom (cut at angle flush with hull). All other original stainless on this Baltic-built boat has held up beautifully so I presume it was top-quality high alloy 316 or 317. I now realize there was no cathodic protection for this tube. This boat design is non-bonded.
The Volvo shaft seal
was last changed 4 years ago; the tube had some deterioration but looked serviceable. The seal had been previously changed in 2004. At that time there was corrosion
along the 10-12mm inboard end of the tube. The corroded area was cut off and the Volvo seal was installed a bit further down the shaft on the still-intact remnant of tube.
is solid fiberglass
, approximately 35-40mm thick in this area. If there is a flange on the exterior hull
(photo 4), it is under layers of vinyl ester and barrier coat applied after osmosis
strip and repair in 2007 (New Zealand's Osmosis
In addition to getting the new shaft log aligned and glassed in properly, the sequence and methods for installation
and alignment (out of and in the water) of the following drive train elements need to be worked out:
- new engine
mounts for the Yanmar
4JH2E, yet to be installed.
- there is a classic
AquaDrive -- the seals
on 2 prior AquaDrives blew out due to less-than-optimal engine
alignment, but no problems for the last 9 years on this unit. I imagine that, at a minimum, the rubber mounting bushings should be replaced.
- adjusting the shaft coupling on the AquaDrive to correct the slight pulling of the shaft downward/to starboard that caused some uneven wear of the old cutless bearing.
- install new Volvo shaft seal.
- find and install new cutless bearing (unfortunately, 1 7/8" strut ID despite the 35mm shaft)
- the current
prop shaft is 35mm diameter, 1.53M long. We are about to purchase
a new FlexOFold, and we are very marginal on clearance under the hull and between the hub and strut. A new, longer shaft may be in order.
- new zincs on the shaft (finally, something easy!)
Oh, wait, and at some point here the rig (currently pretty slack) will be removed to install new electronics
. Putting the mast
up and retuning will tweak the hull.
So where to start? If anyone is willing to chime in on any or all of my questions, here is how I have attempted to categorize them:
1 - Pre-surgery prep: What do I need to measure and analyze, and how, before I start anything else? If I was fitting a new boat
, the placement and alignment of the shaft log would be a given before getting to prop shafts, engine mounts, etc., so it seems my objective should be to make the replacement shaft log exactly as when this Jonmeri left the factory.
2 - Removal
of corroded pipe: Should the objective be to remove the absolute minimum of surrounding fiberglass
, or does that leave a tougher job for bedding the new tube?
3 - Sourcing new tube, fabricating flange (assuming I can't get one from the manufacturer). I don't think I have a good option other than again using a high alloy stainless with about 2mm wall thickness. I need the 54mm OD to fit the Volvo seal (of which I already have spares), and I don't have room for a larger seal (e.g., PSS style). Quality stainless should allow the largest ID for water
flow inside the seal and around the shaft.
4 - Sequence for aligning everything - does this seem right:
1 - Install new cutless bearing in strut
2 - Install new bushings and adjust AquaDrive coupling (is this possible? how?) to true up prop shaft angle (machine shop has already confirmed that shaft is straight)
3 - Install prop shaft with new shaft log tube and Volvo seal threaded over shaft
4 - Center shaft log tube around shaft using shims, wedges -- I assume I want the shaft perfectly centered in the tube? That 50mm tube ID gives adequate clearance for any settling of the boat once it's in the water
, or when the backstay is tightened, rig adjusted, etc.
5 - Does it matter at what point I install the engine mounts and do the on-land alignment to the AquaDrive?
5 - Glassing in/bedding new tube -- is this just a sideways thru-hull, or do I need to use other techniques and materials?
5 - How to provide cathodic protection to the new shaft log?
Thank you in advance,
Alii (Laura, sv ZEN)