Whaler Central - Boston Whaler Boat Information and Photos

Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Fuel Economy

Posted by souweine on 05/13/08 - 9:00 AM

Hi,

I am trying to estimate what my fuel usage will be this summer. I have a 90hp merc 4 stroke with EFI.

I used to assume that (when I had a 2 stroke) 90 hp meant roughly 9 gal/hr at WOT.

Is there an equivlant equation for 4 strokes? Also, how about at cruising RPM's I don't expect to WOT for an hour ever.....

Thanks!

Joshua

Posted by Ric232 on 05/21/08 - 5:55 PM

Yep, there is an equivalent rule of thumb for 4-strokes. It's approx. 9 gph for a 90hp at WOT. :) Direct injection 2-strokes are no worse at WOT, sometimes better.

Posted by souweine on 05/22/08 - 6:57 AM

How about at cruising? 2500 - 3500 rpm?

Posted by wrangler on 05/22/08 - 4:55 PM

It is based on vessel load, people, weight, tide, wind, sea conditions etc.
With a 4 stroke you should use about 3-4 gallons an hour at 4000 rpm. About 5-6 miles per gallon.
I get this on a montauk 17 with 2 people, calm water and staying at 4000rpm.
I have a 90hp 4 stroke Yamaha.

Posted by Ric232 on 05/22/08 - 9:10 PM

souweine wrote:
How about at cruising? 2500 - 3500 rpm?

Best way to get your arms around this is to look at the tests published on Mercury's website: http://www.mercurymarine.com/look_deeper/index.php

Focus on the "BHB" (Boathouse Bulletin) tests. The head-to-head tests sometimes don't provide as much detail. Be sure to look at several tests and average the results. Once in a while, there will be one in there that looks kind of out-of-whack.