HARBINGER, in common with a lot of Walker H28s, has a Bukh 20 horse diesel, which I love because it always starts. It has a beautiful clatter when running and the optical effects of the spinning fly wheel behind the companion way steps are magnificent. That said, I use it as little a possible - in the five years since we acquired Harbinger, Mr Bukh has consumed 200 litres of fuel. The fuel I feed him is laced with BC250 Biocide, and, following a blackish deposit on the CAV filter element in the first year of use, there has been no further evidence of bacterial fouling. Mr Bukh is run for at least half an hour a fortnight under load to keep the batteries up and the bores free from glazing.
I change the engine oil annually, using Castrol RX Super 15W40 (3 litres), and, although I check the gearbox oil level regularly, have only changed it once using Castrol GTX20W50 (350 mL) - I can't see that the gearbox needs more frequent changing with the small amount of work it does. The engine anode at the back of the block is checked several times a year and usually requires replacement every 10 - 12 months - before it is gone completely. I cast my own replacements, melting the remains of hull anodes in a soup ladle onto 27 mm long lengths of 5 mm x 0.8 mm threads cut from bolts, set in a simple mould of 12 mm x 40 mm holes drilled in a bit of hardwood. Engine anodes are also available from Bukh in Sydney at about $20 each or from Discount Seamart in Melbourne for about $10 each.
I have a spare Johnson water pump and impeller on board. The impeller failed recently after at least five years. The impeller had come adrift from the centre bush, but the rubber vanes were in good condition with no evidence of cracking at their roots. The damage may be related to a build up of corrosion under the cover, probably as a result of stainless steel screws used by the previous owner to replace lost bronze ones. I suspect that much advice about replacement intervals may relate to engines used commercially for thousands of hours a year on fishing boats.
Which brings me to the filters: The first fuel filter after the tank on Harbinger is the standard CAV 296 filter with glass bowl and drain plug on the bottom. I check the glass bowl regularly and to date have been fortunate enough to have never found traces of water. The nylon plug for draining the bowl can shear, and I keep a spare plug on board. The Ryco filter number is R2132P. I also buy Ryco filters for the engine oil and fuel filters - about half the price of Bukh filters. The engine oil filter number is Z418 and the fuel filter I use is Ryco R2042P. The engine fuel filter is not listed as an equivalent by Ryco, but it fits (Ryco don't include a new housing seal ring). I change the engine oil and CAV filters annually and the engine mounted fuel filter bi-annually.
A good idea I saw recently was a long length of thin wire down the bore of the plastic drain tube which we push into the dipstick tube to pump out the sump. It stops the end of the plastic tube flexing up and out of the oil when it touches the inside base of the sump.
I hope that the above, based on limited experience, will stimulate comments from other members.