Originally Posted by Xsbank
WOT should be about 1 or 2 hundred RPM below rated maximum. WOT at half power setting makes no sense.
The power installations of many or most trawlers of this vintage make no sense. Oversized engines were installed for marketing reasons and because reduction gears with the proper ratio were expensive and hard to obtain when trawlers suddenly became popular. The boat is seriously under propped so the governer maxes out at about 50% power. The props are the best compromise for the speeds we like to operate at, 7-8 knots, S/L 1.12 - 1.28, 1400 - 1600 RPM, 33-56 HP (18 - 28 each engine).
Going slowly through the long no wake zones of the ICW and harbors would become harder if we added pitch to the props.
When I was designing research vessels like these,
Roger Long Boat Designer and Sailor
Engine suppliers would generally insist on the engine turning within 50 rpm of maximum at WOT if you wanted a guarantee. Modern engines are a lot less forgiving though than the Perkins museum pieces we have.