gallons per hour question...

[2320 pilothouse]

i own a 2120 with a 2 stroke 150 i am thinking about getting a 2010 2320 with a 250 4 stroke .would i use alot more gas on average with the 250 2320 i know its heavier then the 2120 just trying get a idea.is there a chart some where.

thanks

dave

 

[BradV]

http://www.yamaha-motor.com/assets/prod ... 150txr.pdf 2120

Here is what I have experienced. About 21-2400 RPMs is what I call "trawler speed" it's about as fast as you can go without the boat trying to plane. It is useful to "get you there" at about 9-12mph not use much fuel and have people hold a sandwich or a beer. 37-3900 RPMs is my economy cruise 20-22 MPH. I can only estimate but it seems to be 4-5 gph.

42-44 RPMs boat really flattens out and speeds up. It's all over at about 5400 RPMs perhaps due to the prop or whatever. I don't have a need for that speed range too much so I haven't explored changing things around realy. Motor is quiet and content at all speeds and gets a really detailed going over each Fall snd Spring where I keep it (dealer's storage yard and Yammie dealer)

It will definately burn more. If you look around im sure you can find some more stuff on this forum.

[Edited by DH, 'K' converted to RPMs for readability]

 

[2320 pilothouse]

you have the same chart for the f250 4 stroke..

dave

 

[BradV]

No for some reason Yamaha doesnt have it. Do a search from grouperjim and performance or look under the sticky for what props people are running. btw the 225 is so close to the 250 in performance as far as numbers go you might squeak out another knot or two on the top end.

 

[BradV]

found it. This is more realistic real world numbers than what Yamaha has.


2006 2320 F250/bracket

My new numbers with engine in top hole with Merc rev 4 19 pitch are:

400 lbs gas
400 lbs of people
100 lbs of gear

WOT 45mph 5600 rpm
2.6 mpg 35mph 4600 rpm
2.8 mpg 30mph 4200 rpm
3.0 mpg 25mph 3700 rpm


More prop testing. 2006 Parker 2320/f250 same load and conditions as above.

Prop: (3 blade) Merc Mirage Plus/Yamaha SWS (15 1/4 x 19)

WOT 47 mph 5800 rpm
2.7 mpg 35 mph 4600 rpm
2.9 mpg 30 mph 4200 rpm
3.0 mpg 28 mph 4100 rpm
2.5 mpg 25 mph 4000 rpm

Note: Steering with a three blade v. four blade is MUCH easier because the Rev 4 has such a wide cone of thrust (stern lifting prop) v. the narrow cone of thrust on the Mirage/SWS (bow lifting prop). Steering: 3 blade=easier, 4 blade=harder/stiffer.

Also, the mpg/rpms really starts to decay with the Mirage/SWS at 25 mph because of the weight of the boat and the amount of slip as the boat is struggling to stay on plane. The boat is not efficiently on plane until 28 mph with the Mirage/SWS. Anything lower than that is not going to work even with the 12x24 tabs.

For me I have to be able to stay efficiently on plane in the 20-25 mph range due to the steep seas we often get offshore in the Gulf. I'm definitely going to stay with the Rev 4 even though steering is a bit stiffer. I am going to try the Rev 4 17 pitch next and with post data upon completion.

More prop testing. The monsoon finally subsided long enough for me to get out at try a Merc Rev 4 17 pitch.

WOT 44 mph 6000 rpm
2.5 mpg 35 mph 5000 rpm
2.8 mpg 30 mph 4400 rpm
3.1 mpg 25 mph 3900 rpm

Overall I like this prop the best. There is a nice cruising rpm range from 3800-4200 with about 3.0 mpg efficiency. In that range the engine sounds very smooth. There is no significant bogging down in higher seas either. With this prop the F250 pushes along effortlessly. Although 35 mph is less efficient due to the 5000 rpms needed to get there, I don't really get to go that fast in any kind of real sea anyway just basically due to the helm being that far forward on the hull. So, I am happy with the 3.0+ mpg in the 25-28 mph range.

 

[2320 pilothouse]

thanks for the info guys the chart shows a 4 STROKE i have a 2 stroke now is there much difference

dave

 

[DaleH]

thanks for the info guys the chart shows a 4 STROKE i have a 2 stroke now is there much difference

Dave:

Just due to better injection, newer 4-stroke or even 2-stroke OBs with injector technology (versus carbs) can realize a 20-40% efficiency at cruise speeds. Just remember that it takes fuel to deliver rated HP and at WOT or on the high end, ANY motor will burn through fuel like a raped ape.

RPMs around 4K for 2-stroke motors seem to be the typical sweet spot, and somewhat higher on 4-strokes, due to their design and power band. But I'd opine that for best fuel efficiency, stay below 4800 RPMs. A Navman/Northstar fuel computer for < $100 can pay for itself. FWIW, I run Navan/Northstar GPS color chartplotters with the fuel computer built-in and they are FANTASTIC! I get instantaneous readouts (always shows on GPS screen) directly in MPG or N(nautical mile)PG, or can select to read/display GPH too.

 

[2320 pilothouse]

thanks dale,great info

dave

 

[BradV]

If you have a 2 stroke 150 on your boat shouldnt you be able to tell your fuel economy?

 

[Megabyte]

4100 to 4400 rpms seems to be the sweet spot for my 225 OX66.
I'll burn (on average) ~13 to 14 gph at those rpms.

 

[Catfish]

Dave

If I understand your question right I get between 10.85 - 11.15 gallons per hour and 2.25 - 2.4 Miles per gallon. I have a 2008 250 four stroke on a 2520Xl modified vee with a bracket. I know the 2320 has a deep vee and will be a little harder to push. But keep in mind the added weight and beam of the 2520.
These figures are Full Fuel, One passenger, Moderate Gear load and smooth river current with a Rev 4/17 prop, consistantly.

 

[2320 pilothouse]

If you have a 2 stroke 150 on your boat shouldnt you be able to tell your fuel economy?

yes i have a 2 stroke 150 i was trying to find some tests in writing

dave

 

[BradV]

Most of the written test are on the more positive side instead of real world.