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Fuel numbers on Yamaha 90 2 stroke. I have a 15' Sport std model I have redone, now 90% finished. I took it out last night to do a fuel test. The hull only was weighed at 568 lbs. The additional weight of the console, seats, hatch cover, battery fuel and me was approximately 350 lbs. It has a 90 Yamaha 2s weighing 261 lbs less oil, and spinning a Mercury 13 1/4 x 20 Laser II. I haven't installed a tach yet, but wanted to know run time at a certain run speed. I used 2.5 gallons of fuel for a run time of 40 minutes at 24 mph. I figured this gives me 6+ mpg. Water temp was 75°, with 6" chop, little wind. 2:00-1 gear ratio. Does this seem accurate? Thx in advance
Joe, thanks for asking. It is a 15' Sport. I got the 90 Yamaha because I bought a 16'7 Tashmoo that the motor was on and traded up if you will for reliability. It is a 1979 hull with the original 1980 70 HP Evinrude, somewhat tired but hanging in there. So far the Yamaha has done very well except for the 2:1 gear ratio being a struggle for lower planing speeds. I'm thinking of getting a 4 blade SCD POWER TECH to run low planing speeds as I'm told they are stern lifting style props. I rarely open the motor up, but its nice to have a little additional power when fully loaded. 5 adults, gear, 3 dogs (lol) and this little boat takes it in stride! I'm impressed with the " hold up " factor of these classic hulls, even after almost 40 years of use!
I've never monitored it. I have a 12 gallon tank. I never run the boat more than 6 miles at any given run, maybe twice on a weekend, and still have plenty of fuel left. I am curious what you find.
Ran it again tonight with virtually same conditions, weight and fuel. This time I used a GPS cruise speed of 30 mph constant and went for 30 mins so that computes to 15 miles ÷ 2.5 gallons exactly 6 mpg. Not quite as good as the previous at 6+ but not bad. James I would think that you could do that or maybe better with a taller pitch, plus the jack plate should help get a better push angle and less drag if you raise it up. I've got the same size tank so filled, being on the safe side you could easy run 50+ miles round trip. BTW I looked at the performance upgrades. Your right the one kit raises power by a minimum of 10 HP. I think after the new stainless and instrumentation I'll look at the 4" Microjacker. We have a lot of shallow water bars, and coves. Be handy to raise it up so prop doesn't get hurt.
A basic hydraulic steering system is my best recommendation for an upgrade though. I love it. I used this one http://www.ultraflexgroup.com/easySto...hedaID=537 it's probably more than what is needed. I liked it because it was silver in color
That steering setup is NICE! When you back down off plane do you have to watch back wash over stern? Or does your weight forward compensate? I did the quick math and motor + plate goes 350+-. Plus being leveraged 4". You have some very nice upgrades. Have you done anything to your hull?
Hull has been modified, extended strikes and a running pad. Water comes over the stern when the motor is jacked all the way up and I hit reverse or if just me in the boat, and I stand in the back. Water will fill the tub and eventually overflow. Otherwise, under normal circumstances it doesn't come in. My motor weighs a bunch more than your Yamaha I think. I would call it a problem, but it doesn't matter to me, it's a river taxi, and I usually have a bunch of kids or adults in it just idling in a no wake zone.
