Fuel Economy question?

[VCinRI]

I have a 27' Sailfish with twin 225 Yamaha's SWS, FI, 1997's.

I believe I am averaging about 1.2 MPG. 3800-4000 rpm cruise, @ about 28-30 MPH. Does this sound about right.

Would there be much of an improvement if I went to Four strokes in the future?

Thanks,
VC

 

[megabytes]

I had the exact same boat. My average was a bit more at a bit faster RPM. I would cruise (conditions permitting) at 4000 and sacrifice just a tad of economy at 4200 when it was really nice. At this setting I could generally get 1.3 - 1.4 MPG and run 30 kts which is a good deal faster then what you are seeing. This is with tabs all the way up, 4 bars on the engine trim, and generally full load and fuel.

In flat, protected water like the ditch I saw 1.5 mpg on occaision running at 4K RPM. Note my numbers are in nautical units based on the FMS setting.

 

[Tuna Man]

Mega, I think your boat did not have bottom paint is that correct? Assuming VC's boat has bottom paint this might explain some of the loss of speed/performance.

If you switched to four strokes, I think you would reduce your overall consumption by about ffifteen percent. You may save a little more if you troll a lot and save a little less if you run at full throttle often. I'll let you decide if investing in new engines makes sense or not for your usage.

 

[VCinRI]

Yes, I am bottom painted. Range was my real concern. I heard a fellow Grady owner with four strokes question my range compared to his. (same boat).

It got me thinking.

Thanks for the info.
VC

 

[ocnslr]

We purchased our 2002 Islander new with a single 250HP OX66. With a loaded boat, we could consistently get 1.2nm/gal, at a 22-25kt cruise - depending on conditions. It would quickly drop down towards 1.0nm/gal if we needed to push the bow down into a chop.

We wanted to fish offshore, but with only a 150gal tank we would be rather limited in where we could safely fish.

With 465 hours on the OX66, we repowered with twin F150s. With the same heavy boat load we now cruise at a faster 25-28kts, getting 1.6-1.7nm/gal. This improvement in fuel economy has enabled us to run 75nm offshore and back, with or without trolling, and we have never burned more than 114 gallons.

We did not repower to save money - could never pay the cost of the repower even with current fuel prices. We repowered to extend our range, and the 35-40% improvement was everything we hoped for.

Brian

 

[Fine-A-Lee]

I have 2 250 4 strokes on a 2006 Marlin 300 and at the most have gotten 1.3mpg after trying all tab & tilt settings.
Ken

 

[Tuna Man]

Ken,
Welcome to the site. Hate to derail this thread, but I just looked at my notes from a test we did back in June. We hit 1.4mpg at 3500, 1.5mpg at 4000 and 4500 with the same setup as you. Boat is bottom painted, but was lightly loaded in smooth water on a 75 degree day.

 

[ocnslr]

When reading posts referring to fuel economy, be sure to differentiate between MPG and nm/gal.

Multiply nm/gal figures by 1.151 to get MPG.

Sorry, but my charts are in NM, and all my instruments are set that way..

 

[megabytes]

Correct. My 97 272 did NOT have bottom paint.