I was recently asked, "What is better for my motor yacht, jet propulsion or traditional twin screw diesels?”
My answer was, “That depends on whether you want performance (speed) or cruising economy, and that is further affected by the size of your yacht.”
In the early 1990’s water jet propulsion, with its increased speed derived from the same horsepower, was the new model for performance motor yachts. But, jet drives have recently fallen out of favor as the optimal propulsion for cruising yachts over 100 feet.
On the other hand they are still an enticing choice for mid-sized performance yachts in the 70 to 90 foot range (like the Riva 86 domino or the Pershing 74) especially when the increased engine life which a jet driving diesel will have is factored into the buying decision. When the boat will be spending 85% of its time operating at full speed the jet drive, and only operated at the less efficient slower speeds near the dock, then a jet drive is simply the optimal choice.
But, for cruising yachts carrying large fuel loads, which are normally operated at slow and medium speeds jet drives are not a good choice. This is because a jets fuel economy at high speed or slow speed is nearly identical to their high speed consumption. By contrast, a traditional twin screw diesel installation can increase its fuel economy by a factor of three at lower speeds. Consequently, for owners of large motor yachts jets no longer have the same allure as 20 years ago.Read more
US Sailing published a report cited on page C2 of the August 9th edition of the San Francisco Chronicle, discussing the loss of the racing vessel Slow Speed Chase in the Farallones earlier this year. The report stated that,
"If the crew of Low Speed Chase had sailed in deeper water, they could have prevented the tragedy".
The report cited "Failure of seamanship in negotiating shoal waters on a lee shore", as the main safety issue in which the crew failed to consider the risks associated with waves at that depth of 28 feet. As a result of this failure five people were killed. Yet, what happened to this boat was predictable and foreseeable.
Sailors with many years of experience sailing inside SF Bay often know how to successfully predict winds and currents, and do so quite accurately, including foreseeing counter currents and back eddies. Such experienced racers can predict how the wind will channel around capes and bluffs, and by watching the amount of overcast or clear skies can tell you how windy it will get later that afternoon. Their ability comes from studying the principles of winds and currents and through experience applying these principles to racing on SF Bay.Read more
In an earlier blog I discussed where to get parts for older boat engines and since then another valuable resource has come to light.
L.A. HARBOR MARINE, located in Wilmington, is the Gray Marine Authorized West Coast Distributor, and they carry everything for Gray Marine engines, including rebuilt engines, tune up parts, starters, transmissions, engine parts, engine manuals, gaskets, manifolds, and engine logos. And they rebuild engines, and people ship their engines to them from all over the U.S..
They also have many parts for ChrisCraft, Chrysler, Chevrolet and Hercules engines, all fo which they also rebuild. They also represent Velvet Drive transmissions, and an assortment of other marine hardware items.Read more