The issue is not thermal destruction but rather saving the exhaust manifold and gaskets. If the QSM's had wet exhaust we wouldn't be talking about it. I just put the 52DB back in the water last week; had the props, shafts, bearings, couplings, and seals refurbished/replaced as well as the bottom done. When the props were in the shop I had 75-100 RPM added to the engines. No hard fuel data yet but went from 2250RPM at 99% load and 27.2 knots to 2420RPM at 95% load and 30.4 knots full fuel and water. Bahamas trip first of Sept so better data after that. The boat liked 1800 RPM before; we'll see where it want's to run now.So he's lowered his GPH recommendations even further? I haven't run across that yet. But that's not a good sign. That seems to imply that the engines are destined to eventually thermally destruct, and that it's just a case of when that happens. By continuing to lower fuel burn recommendations are we just trying to prolong the "when" as far as possible?
20-22 knots is a fine speed, especially for the size of the boat. The Cats can safely cruise faster, but they aren't without their issues, too. Glad to see these recommendations still produce cruising speeds over 20 knots!
I'd love to hear numbers from other Cummins owners, too!
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