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Old 12-06-2015, 12:43 PM   #124
Art
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City: SF Bay Area
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 12,569
Quote:
Originally Posted by bayview View Post
Art: Are those gassers? extraordinary mileage if they are.
Yup! Not really extraordinary mileage. Top condition engines - 350 cid / 255 hp each. Very clean bottom, correct props, little over half load aboard.

With one engine only running at low rpm and moving boat through water at just 5 to 5.5 knts... in calm water, with other prop left freewheeling (BTW - BW VD tranys allow that).. 2.75 to 3 nmpg is attained. With twins running at low rpm for 6 knots 2 nmpg becomes avg. 7.58 knts is our Tolly's calced hull speed (at 7 or just above speed running twins we get only 1.5 nmpg) For full plane at 16 to 17 knts Tolly averages 1 nmpg.

Well designed planing hull, good condition gassers, clean bottom, correct props, and not too much carry-on load = OK mileage in the water. Being able to plane out at 16/17 knts or above speeds when desired or needed can be priceless. That is speed we travel when long distance needs to be accomplished from dawn to dusk.

One time I needed to run quickly away from oncoming and potentially horrific multiple boat traffic problems. WOT at 21/22 knts really helped out... only needed that speed for a short duration... minutes.
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