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Old 11-30-2010, 10:50 AM   #19
Egregious
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City: Sunset Beach, NC
Vessel Name: Polly P.
Vessel Model: Monk 36
Join Date: Feb 2010
Posts: 555
RE: New Guy needs advise

Quote:
FF wrote:

Usually the rating of the engines will show the style of cruising service the boat was designed for.

A 36 ft boat with 100 hp is going to be really cheap at the Sq RT of the lwl, say 6k for LRC.

Hull speed will double or more , the burn for an extra K or 2.

If the 36 ft boat boasts 350 hp, it was designed as an inshore weekender , the speed will be double the small engined boat 15K but the fuel burn will be 10-15 times higher.

On unusual boats , where you cant simply ask owners , a quick math will work.

Find the vessels displacement , that is how much it weighs (not the USCG "tons" which is volume).

Divide the weight in pounds by 2240 for the displacement in tons.

Slow cruise will cost 2 or 3 hp per ton, so multiply the tons by 3.

Then divide that number by 16 for a diesel or 12 for gas.

This will give a rough GPH at normal cruise.
This method was right on for my boat.* This calculation is very close to actual fuel burn at slow cruise.

*
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