I intend to start two separate threads: Why or why not change out your diaphragms, and how I did mine. This is the first.
From my own experience and from posts here, I suggest the reasons we change them out are:
1. They have begun to let water
either into the boat or at the sensor that says there is water
between the two seals
2. They are old, and either an insurance surveyor
or the manufacturers' agents says it is time.
Number one, is a no brainer! I am not sure what could create a leak in the lower diaphragm
- they are outrageously hardy - but it is obvious from some other posts here that it can happen. Of course, leaks
in a boat must be addressed.
Number two, well, I now have trouble with that. I just changed the diaphragms on the two saildrives on Cat Tales, a 1996 FP Tobago
35. It was dreadfully hard to do, and the equipment
appears to be in fantastic shape - like new - after 20 years.
The best information on the web seems to suggest that Yanmar
every two years and total replacement of the stuff every 6 years. As a result, if you have your boat surveyed every 5 or so years for insurance
purposes, and the surveyor
is worth anything, you have to demonstrate your effort to stay on the manufacturer's schedule.
is really difficult. I guess you could sacrifice the lower boot and inspect the lower section with a mirror and good lighting
; and remove the straps on the upper diaphragm
and inspect the upper part of the lower section and the upper diaphragm completely. This method might only cost you $500 US or 400 Euros, as the boot usually rips, and the two straps are not allowed to be used after removal
Not that I'd do it, but I can see how someone might simply say to himself that he has tested the water sensor, and since there is no water between the two diaphragms, I have inspected the installation
- and say to the surveyor that he has done so.
Replacement after 6 years? That means a new lower, upper, two straps, and the boot that provides fairing against the outer hull
. That costs ~1000 Euros per saildrive
, if you do it yourself.
If I was not attempting to maintain my insurance, and knowing what I know now, I would not spend the money
. I swear, all parts
were in excellent shape, no different from the new parts