surprised the tri doesn't burn a bit less, Larry. What prop? I have a Volvo D2-75 saildrive, that's 75 hp driving a 20" 3 blade feathering Autostream, 30,000 lb boat. I run at about 1950 rpm and make about 6.7 in calm, down to 6.3 or 6.4 with a 15 knot headwind. The burn rate is quite consistent, over about 500 hours now.