eyschulman
Guru
- Joined
- Apr 1, 2014
- Messages
- 1,288
I am reopening a old can of worms. the issue of the fuel burn of a single motor Vs twins. Theoretically on the same boat the single should be more efficient and the motor size closest to the HP needed should be the most efficient. What I have noticed over and over again is that on a practical real world basis this is not always the case in any significant measure particularly if similar but not identical boats are compared. I see many circumstances where twins even large twins do as well as single engine boats. As an example that is not in any way unique we can compare the fuel burn published for the Helmsman 43 at approx. 35,000 lb disp. against my boat at 48 ft and approx. 35,000lb disp. The helmsman has a single 370 HP engine and my boat has twin 330 Hp engines. The Helmsman at 8.3K burns 4.9 G/Hr and at 9.5K burns 8.4 G/Hr at 10.5K the burn was 16.3 G/Hr. Compared to my boat we find 8.3K at 4.4 G/Hr and 9.6K at 7 G/Hr and 10.3K at 11 G/Hr. There are realistic reasons against twins but for me the fuel efficiency argument does not fly. I am of the school that believes the boat and prop or props will demand x amount of power for y amount of speed and the x from one or two engines is pretty much in the same ball park in real world terms and whatever drag and lose from two engines is not significant to speak against twins.