best fuel economy

berryst · Posted: Thu Nov 03, 2011 12:52 pm Post subject: best fuel economy

I know that this topic has been covered in the threads but I am still confused and I know there are many of you that are a lot smarter than me about this.

What is the best speed for the best fuel economy in the 22 CD, 90hp 4stroke, angler..loaded....?

Is is best to get up to a plane? Putt along? Cruising speed?

I see much about props and load etc. Perhaps there is no right answer.
I see charts but they don't seem to apply to me. Do I just get a flow meter and figure it out?

Chris

Wandering Sagebrush · Posted: Thu Nov 03, 2011 1:28 pm Post subject:

Chris, here's a link to the factory performance stats for the Classic Angler. The data are for twin 40s, but the single 90 is not that much different, if I remember correctly.

ferret30 · Posted: Thu Nov 03, 2011 1:44 pm Post subject:

From c-dory.com:

Single Honda 75 Hp Four Stroke
RPM GPH MPH MPG NMPH NMPG
2,500 1.50 8.5 5.67 7.4 4.87
3,000 2.40 12.5 5.21 10.9 4.48
3,500 3.10 16.2 5.23 14.1 4.49
4,000 3.85 20.3 5.27 17.7 4.53
4,500 4.70 24.7 5.26 21.5 4.52
5,000 5.60 27.6 4.93 24.0 4.24
5,500 6.80 30.4 4.47 26.4 3.84

Probably similar for a 90?

tpbrady · Posted: Thu Nov 03, 2011 5:25 pm Post subject:

The factory table is very optimistic but if plotted on the graph for a carbureted Honda 90 should have the same basic curve. The best fuel economy is at hull speed, just shy of about 6 mph. The best economy on plane is 21-24 mph. The fuel injected 90 Honda has a completely different fuel curve.

berryst · Posted: Mon Nov 07, 2011 1:08 pm Post subject:

well.... from what I see the factory table must be going with the wind. the tide, staying on the down hill slope of the wave, empty boat, driven by a midget, just before it ran out of gas (to lighten the load) and going with the rotation of the earth made by a guy selling boats who was later indited for misrepresentation just before he left town never to be seen again just after he sold the factory.

Chris

ferret30 · Posted: Mon Nov 07, 2011 1:42 pm Post subject:

I noticed over the weekend that my 22 Cruiser doesn't make it over 17nmph (according to GPS) when running at 4500rpm with a Suzuki 90. That was with 4 people on board though... That's a lot lower speed than what the table says for a 22 with a 75hp Honda at the same rpm!

starcrafttom · Posted: Mon Nov 07, 2011 2:47 pm Post subject:

I logged 1000plus hours on my 22 with a 90 honda. I never got the numbers the factory claimed. I burned 4.5 gallons a hour at 20 mph for a 4.4 mpg. if you need it in knots you do the conversion. I cant think in knots.

Those number were on a good day with a heavy but not really heavy load. My susan can load a boat.

On the one time we had 5 people on board I could not get over 15 mph and every time I hit a wave we lost ground. As some point you can overy wieght the boat. We had a lot of gear for camping and we are all big people 220 Plus. so maybe 1100 of people plus full tanks. Thats a lot ot ask a boat to do.

A Fishin C · Guest

Personally I never get the speed per RPM's that C-Dory or some of you get. Whether with 15 or 17 pitch prop. 4500-4600 RPM 18-20 mph not knots. 3 guys and fishing gear, new bottom, Yamaha 90. My fuel economy is good, just not fast. 20 mph at 4000 rpm with just a Honda 75(factory no.s) I just don't see how it is possible. Unless maybe our waters are less viscous up here in Canada.

Chris, thanks for your hilarious post.

JGrider · Posted: Tue Nov 08, 2011 12:34 am Post subject:

[quote="A Fishin C"]Personally I never get the speed per RPM's that C-Dory or some of you get. Whether with 15 or 17 pitch prop. 4500-4600 RPM 18-20 mph not knots.
Me too. I have never gotten my RPMs on my Honda 75 over 4900. I have been running a 15P and I think when I get the chance I will try a 14P. I know I could not gain any RPM with a 17.

jennykatz · Posted: Tue Nov 08, 2011 7:03 am Post subject: props

What you might need to do make sure that your bottom is clean without sea growth then take everything off your boat you dont need . make sure your engine is tuned up then take it out and do WOT runs make sure the engine at least turns the min rpm actually it should be in the upper range like 5500-6000rpm then as you reload the boat you will loose some of the rpm with weight If you are loading your boat down you might need to go to a 13pitch prop to get it up to 5500rpm
A good prop shop will let you experement or borrow from other c-brat
On our cd-22 cruiser we had a Suzuki 90 (actually a 100hp) that we had a 14by 18 pitch prop we got over 5mpg statute and could get up to 34-36 mph Now with a Honda or Yamaha you need to go down a pitch or so because the suzuki has a bigger gearcase so it will throw a bigger prop another reason to go Suzuki
ON my cape cruiser 23 I have Yamaha f-115 with a 13by 15 pitch prop I only get 5500rpm and 30-32 mph and about 4-4.5 mpg

20dauntless · Posted: Tue Nov 08, 2011 9:29 am Post subject:

Here's info from BoatTest.com on a 2008 22 Crusier with a Honda BF90D.

berryst · Posted: Tue Nov 08, 2011 11:56 am Post subject:

tpbrady · Posted: Tue Nov 08, 2011 6:38 pm Post subject:

If you look at the chart closely you will see fuel consumption go up dramatically between 3500 and 4500 rpm. Up until that point, you see every 500 rpm increases consumption by .8 to 1 gph. Between 3500 and 4000 it goes up 1.8 gph. Between 4000 and 4500 it goes up 2 gph. Between 4500 and 5000 it goes up 1.1 gph. When I had a Honda BF90D on a 22, this meant you traveled either 14-15 mph or as fast as you could go because of the big jump in fuel consumption that was right around 3800 to 4000 rpm depending on how heavy the boat was. The fuel graph on the older BF90A was more linear. If you look at the first chart you see the most efficient speed when on plane on the BF70A was around 24 mph. That doesn't hold true for the BF90D where the most efficient speed is 10 mph slower.

JamesTXSD · Posted: Tue Nov 08, 2011 6:55 pm Post subject:

Probably a factor of our hull designs, but we do notice a similar situation with our 25; but the fuel burn in mpg is markedly better at displacement speed (around 6 knots on our boat) as compared with the near linear fuel use increase with speed with the 22 as shown on that chart. We are most inefficient just before the boat goes on plane, a definite improvement as the boat comes on plane, a little blip at about 16-17 knots where the fuel use is better than below or above that speed, dropping slightly as speed increases. At displacement speed, we get 5+ mpg... drops to about 2 as we get on plane, gets to around 3 at the sweet spot, then drops from there.

This varies with conditions; a fuel flow meter helps to get the boat set with trim, attitude, and rpm for best fuel burn.

20dauntless · Posted: Tue Nov 08, 2011 7:31 pm Post subject:

My experience with the BF90D is similar to tpbrady's. When the VTEC engages and lean burn control disengages, fuel burn jumps quite a bit. Notably, I think this is not at a fixed RPM but rather at certain engine loads. I can run at 4400 RPM and around 20 knots alone on the boat and sip fuel. With 8 people and weekend gear I can still run at 4400 RPM but only get 16 knots and burn a lot more fuel.

I don't have a fuel flow meter on board so I don't have precise figures, but this has been my experience baased on 300 or so hours.