this idea here just in case someone runs into the same problems I had measuring up for a new dripless shaft seal
. I am avoiding using abreviations for critical bits (the meta data) in the hope that anyone searching will find this thread and it might help them out. Someone might already have posted a similar idea, I just could not find it.
Of the two dimensions needed, the shaft diameter was easily obtained with a set of calipers (OK, yeah, I tried to measure with a shifting spanner first, my bad, I won't be that lazy that again.)
The stern tube was REALLY difficult though. First, the boat is in the water
, so I didn't really want to pull the seal off the stern tube to take the measurement. Aside from the water
everywhere, I could not be confident of getting it back on again as it of an unknown age and therefore not very trustworthy.
Second, access to my sterntube is a bit of a nightmare. It is a long way down in the keel
, nearly two feet below the level of the cabin sole
, and there was simply no room to get the calipers close to the critical bit, regardless of the fact that the bit I needed to measure was also covered by the dripless seal and fenced off by the bolts holding the sterntube to the bulkhead.
One person suggested a piece of string wrapped around the tube tightly, to determine the diameter, but because of the access, and the old grease, I did not feel I could get a very accurate measurement that way. I may have been wrong, it just did not feel right.
So, I cut out a series of horseshoe shaped guages from a sheet of reasonable thickness tin, in incremental sizes from a size below what I estimated the diameter to be, to a size above. These were thin enough to slip between the face of the sterntube bracket and the edge of the dripless seal without disturbing the seal itself and the arms of the horseshoe were narrow enough to fit between the tube wall and the bolts holding the the sterntube flange in place.
Clearly these had to be cut out fairly accurately, and I had to make a call on whether my system was likely to be metric or imperial, pretty easy for an old Australian boat like mine, not so easy for something newer I suppose.
So, in my case I estimated it was a two inch stern tube (as I had a 1.5 inch shaft) so cut out a 1.75" (probably pointless, but I had to be sure), a 2.0" and a 2.25" horseshoe.
As it turned out, neither the 1.75" OR 2".0" would fit but the 2.25" fitted nice and snugly.
Now I have ordered my replacement PSS seal, and in a few days I will know if I was right.
(I will update this thread or hopefully remove it completely if I am wrong. What is the price
paid to the mods for removing self incriminationg posts I wonder...?)
I hope this helps someone in the same predicament.