before - the standard volvo coupling
Warning: high yawn rating ;-)
Following our lift in Manoel Island Yacht Yard where we had both cutlass bearings replaced we have been keen to realign both our prop shafts just in case they were out and causing undue wear on the new bearings.
The actual exercise is relatively straight forward to undertake but like most things relatively time consuming requiring the coupling that joins the propeller shaft to the gearbox to be split (unbolted) and parted slightly so that a feeler gauge can be inserted around the flange at 90° increments. In an ideal world with a perfectly aligned engine and shaft the gap would be consistent but if it isn't the engine needs to be raised or dropped, angled up or down or moved left or right or any combination of these movements - a bit of a dark art as one of our cruising friends commented.
On Flirtie, access to the bolts to split the coupling is rather awkward in the first instance so no surprise the alignment exercise hasn't been performed in long time. What we really wanted was a solution that makes the job easier and this is where the "R and D flexible coupling" www.randdmarine.com/flexiblesc.asp
The R and D flexible coupling negates the first exercise of unbolting the coupling and instead provides you with a designated area (a machined red bolt) that you can insert a feeler gauge above and measure the gap. This means the gap can be monitored at leisure and any minor adjustments made as necessary. Additionally the coupling is semi flexible meaning it absorbs minor alignment errors of up to 0.25mm - a benefit certainly but not completely necessary.
The installation was relatively straightforward with the help of the clear instructions www.randdmarine.com/flexiblescinstr.asp
. The only minor inconvenience being the new bolts that connect the coupling to the gearbox flange needed shortening by about 4mm to clear part of the gearbox casting. This was fairly easy for us with access to mains power and an angle grinder but would be a bit of a pain with only hand tools.
after - the white nylon coupling between the two halves of the standard coupling
With the installation complete and with just a minor tweak to a couple of the engine legs the gap is almost identical at all 90° positions so we're now ready for a proper sea trial ;-)