Tohatsu 6.0 Long Shaft performance . .
Posted: Tue Aug 21, 2012 11:07 amTattoo has mounted on its [cutout] transom a 6 hp Tohatsu long shaft. If you just need to get in and out of the marina, then that's a lot more power than you need. But for crusing where you want to get somewhere to anchor or meet others, and the wind and/or tide are adverse, then its my opinion that you need at least 4.5 hp and a little more doesn't hurt. Tohatsu has a 4.5 hp version, but it's identical to the 6 hp except for its compression ratio. The 6 hp is developed at 5,000 rpm using their low pitch prop. My engine maxes out at 4,920 rpm -- so it's very close to its specifications. A higher pitch prop wouldn't reach its rated hp. And the engine pushes Tattoo close to its hull speed starting at a about 4,200 rpm. The lower pitch provides more torque when needed against waves and strong head winds.
I can now report actual measured performance data. At the end of July I cruised from Colonial Beach, Virginia, to Leonardtown, Maryland, to visit my son and family. It's about 17 nm one way. The tide and wind were against me and if I attempted to sail the distance, I wouldn't have made Leonardtown before dark and I'd have missed a wonderful crab feast.
By measurement on my shop's "bathroom" scale, Tattoo used 13 lbs of fuel (calculated as 2.1 gal @ 6.2 lbs/gal). I set the engine to 4,000 rmp and Tattoo usually made about 5 knots. Round-trip transit time was about 7.5 hours. That's about 1.7 lbs per hour. Tattoo's gas tank holds 3.1 gal, giving it a range of about 55 nm. I carry a 1.3 gal reserve of gas in a separate container. If I set her at 3,000 rpm -- the speed would only drop to about 4.5 knots, but the fuel consumption would improve dramatically. Maybe oneday I'll have occasion to get the same data at 3,000 rpm.
I can now report actual measured performance data. At the end of July I cruised from Colonial Beach, Virginia, to Leonardtown, Maryland, to visit my son and family. It's about 17 nm one way. The tide and wind were against me and if I attempted to sail the distance, I wouldn't have made Leonardtown before dark and I'd have missed a wonderful crab feast.
By measurement on my shop's "bathroom" scale, Tattoo used 13 lbs of fuel (calculated as 2.1 gal @ 6.2 lbs/gal). I set the engine to 4,000 rmp and Tattoo usually made about 5 knots. Round-trip transit time was about 7.5 hours. That's about 1.7 lbs per hour. Tattoo's gas tank holds 3.1 gal, giving it a range of about 55 nm. I carry a 1.3 gal reserve of gas in a separate container. If I set her at 3,000 rpm -- the speed would only drop to about 4.5 knots, but the fuel consumption would improve dramatically. Maybe oneday I'll have occasion to get the same data at 3,000 rpm.