Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: fuel mileage 15' Classic/90 2stroke
Posted by Jeff Lohr on 06/23/16 - 5:54 PM
#1
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
Posted by Joe Kriz on 06/23/16 - 6:02 PM
#2
Jeff,
A couple of questions.
What is a "Standard Model" for your 15' ?
http://www.whalercentral.com/userphot...allery.php
The 15' models were rated for a MAX HP of 70
So, there aren't very many people here, that I know of, that have a 90hp like you and jamesgt727
Hopefully some engineers or others with a similar setup can help you out.
Sounds too fast for me as I am not a speed demon. :-)
Posted by Jeff Lohr on 06/23/16 - 6:56 PM
#3
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!
Posted by jamesgt727 on 06/24/16 - 4:16 PM
#4
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.
Posted by Jeff Lohr on 06/24/16 - 6:18 PM
#5
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.
Posted by Jeff Lohr on 06/25/16 - 6:03 PM
#7
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?
Posted by jamesgt727 on 06/25/16 - 7:54 PM
#8
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.