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| Damaged piston and the replacement, complete with new rings |
After having suffered an engine seizure due to salt water in the cylinder, David Lillistone (son) and I carried out an overhaul replacing the piston and piston rings, exhaust valve and seat, plus a multitude of other components. In addition, I had a new bronze propeller made by Austral Propellers, with consultation and calculation provided by William Olds and Sons (Olds Engineering) in Maryborough. The service provided by Olds Engineering was exceptional, and they acted on my behalf in dealing with Austral. http://www.olds.com.au/
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| Three generations of the family worked on the engine overhaul... |
The engine is now starting to be run-in, although I believe she will continue to improve for a long time yet. The original propeller was a 12" x 10" re-pitched to 12" x 8". The blades were of the Yanmar pattern, but the replacement is a 12" x 8" from the start, with about a 55% disc- area ratio.
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| Original Yanmar-pattern propeller.... |
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| ....and the new Austral prop supplied by Olds Engineering |
Performance is continuing to improve with use, but the boat has gone from a top speed of 6.1 knots/7mph to 7.3 knots/8.4mph. That is at maximum engine speed of 3600rpm, but at maximum continuous of 3400rpm continuous speed falls back to about 6 knots/6.9mph and at my preferred cruising speed of 2800rpm, we run at about 5.5 knots/6.3mph. Those 2800rpm speeds are quoted from memory, but I have got them recorded somewhere.
When we are bird-watching, or just cruising the shoreline, or favourite engine speed is 2000rpm - the engine is like a sewing machine and the boat runs at a very pleasant 4.7 knots/5.4mph.
Sweet boat Rossco.Notice the exhaust on the fast run,she's spitting out raw diesel as they do when working harder than needs be trying to beat the drag at a speed she does not like to run.Bit like cruising a Tiger.As you know,1900 rpm'll give around 78kts & full throttle will give you around 78kts too!The original "constant speed variable noise machine"!Finding the sweet spot for power/speed with those little diesels gives a very smooth & pleasant ride.I thought I detected a vibration period on the fast run,but maybe it was just the audio quality.You're getting quite a collection together.Al.
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