34' Tollycraft at 17,000 lb. when dry, approx 21,000 fully loaded.* Twin 350 cid / 255 hp Mercruisers in tuned, top running*cond. Two 100 gal*alum gas tanks = 200 cap:
Either engine running alone and*traveling quite*slow (5.9 to 6.2 knts)*avg near 3 nmpg.
Both engines running...*at*6.7 to 7.3 knts (just below hull speed of 7.58 knts) we avg 2 + nmpg.**
Fully on plane at 16 +/- knts she gets 1 +/- nmpg; but*that can quickly get expensive these days.*
Higher rpm, quads begin to open -*never tried it long enough*to calc nmpg, probably can't count that high anyway - LOL.*
But... when speed is necessary she will top out*(WOT / 4,500 rpm) at over 21 knts.* So far only had to stress her real hard once to solve*a potentially disastrous developing*situation of dumb boaters while we were helping to usher Tom Perkins Maltese Falcon under Golden Gate Bridge and into SF Bay.* I kept her nearly opened up for a couple minutes, until out of the danger zone!* Only other time I hit WOT was during sea trial, then held her just slightly back at 4,400 for*a few*minutes.* I would not doubt that 40 to 50 gph is her fuel consumption at that speed... OMG!
Currently, due to weight/nmpg results, we generally cruise at or below hull speed keeping tanks under 50% full and put some gas in at 15 to 20% reserve.* Soltron fuel additive has worked wonders for our fuel system.* Weve been using it for a couple years and our fuel stays fresh with no water and no gunk build up, such as previously would occur.* During first half year of use Soltron cleared up gas problems wed been experiencing on regular basis... and has kept it that way!* Also great for diesel.*
http://www.soltron-gtr.com/english.htm
So... Our Crusing Range(s):
-****** At 6.2 knts; well below hull speed w/ one eng running... 500 +/- miles
-****** At 7 knts; just below hull speed w/ both eng running..... 350 +/- miles
-****** At 16 knts on full plane.................................................... 175 +/- miles
-****** At nearly WOT ................................................................. Forget About It!! *