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Old 10-19-2014, 07:09 AM   #6
caltexflanc
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City: North Carolina for now
Country: USA
Vessel Name: Small Incentive
Vessel Model: Boston Whaler 130 Sport
Join Date: Aug 2011
Posts: 5,358
Two 8v92TI's on my 60' LOA, 75,000+# Hatteras 56MY . At seven knots, 900-1000 rpm around 7 GPH total , but typically run at 8 or 9 knots, 1300-1500 rpm 10 GPH total. Designed to be a planing boat but we never did, nowadays it would euphemistically be called "semi-displacement". Running them up once at the end of the day for 10-15 minutes to 1800-2000 kept them very clean and happy, got a very thorough survey at 3000 hours, came out great. Maybe engines in poorer condition need more frequent high RPM runs, mine certainly did not; I could skip a day or two and the smoke would clear up in a couple of minutes.

Given the size of the boat in the OP, but now knowing the hull form, 10-12 GPH at say 8 knots may be about right (all GPH do not include generator use). Want better economy, get a smaller, narrower, true full displacement boat and go even slower. At some point, it takes X amount of horsepower to move Y amount of boat at Z amount of speed.
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