3807 Fuel Burn

J

jdkohnke

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Dec 30, 2007
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29159
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I have an '87 3807 with Crusader engines. I have seen various references in this forum to somebody having compliled a "Fuel Burn Chart" for this model. I would love to see it if you have one...

Thanks in advance,

Jeff
 
Oasis shared his with me several years ago.
Basically, as I remember, running at around 1800 RPM's which gives me about 8 knots (hull speed), I get about 1 mpg. Run the engines up to cruise speed of about 15 knots - 3200 RPM's and my mpg went down to less than 1/2 mpg. Since we saw his printout, we only run at hull speed. I've got better things to do than just buy gas for the boat.
FYI, I have Merc's but I'm sure the fuel rate is about the same.
 
This is really helpful. Thank you very much for sharing the info. I have suspected that was the case, but will continue to run at about 1,800 during my leisurely cruises!
 
It takes a lot of gas ($$$) to run that boat at planing speeds. To run 50 miles at planing speed, you are looking at around 120 gallons and let's say $3/gal is $360. Drop it down to hull speed and you're looking at $150. BIG difference.
Maybe Oasis will see this and repost his spreadsheet.
 
When I bought my 38' Santego (454 Crusaders) four years ago, a helpful fellow, (can't remember his name darn it), sent my this chart:
RPM *GPH MPH Cruising Range Cruising Hours
650 2 4 432 Miles 108 hrs 0 min
1000 3 6 432 Miles 72 hrs 0 min
1500 7 8 247 Miles 30 hrs 51 min
2000 10 10 216 Miles 21 hrs 36 min
3200 32 23 155 Miles 6 hrs 45 min
3500 36 25 150 Miles 6 hrs
4400 50 30 130 Miles 4 hs 19 min
From this chart, looks like hull speed and best efficiency is somewhere around 1000-1200 rpm. I typically run at around 1250 and have avg. around 1.8 mpg at that speed. There is very little wake, you can feel that the boat is not "pushing". Anything above that and the wake starts to increase and it is definitely starting to push water and suck more fuel.
 
Jeff,
In order to determine your burn rate, you need to tell us what engines you have. Crusaders have various engines. What size engines?
 
When low in gas and leaving a destination last week, a friend (and fellow USPS member) suggested cruising at 6 knots back to the marina instead of my normal 18 knot cruising speed at 3200 RPM on my 93 Mariner, since I would burn about 6 GPH instead of 18. It sounded good and I started out at 6, but when thinking on it, what do I save if it takes me 3 times as long to get back?

What am I missing on the burn rate? I certainly see the difference if going out for a certain number of hours, but don't see a gain if going to a destination.

Stu
 
Stu,
It takes a lot of extra power (gas) to get a boat up on plane. Look at any boating magazine that has boat reviews and specs. You will see miles per gallon is always much higher when the speed is hull speed or less.
On my 3807, MPG's at 7-8 knots is more than double MPG's at 15 knots.
 
Check out the following web site. It has a very interesting formula for calculating hull speed.

www.psychosnail.com/BoatSpeedCalculator.aspx

Bob
 
quote:
Originally posted by Starry Night

Jeff,
In order to determine your burn rate, you need to tell us what engines you have. Crusaders have various engines. What size engines?

Click to expand...


I have the 7.4L Crusader 350's (454 C.I.D).
 
I understand now, probably burn a lot less at lower speeds than I thought, which was verified in the following reply from Crusader when questiong going to a destination 18 miles away as an example. I have twin Crusader 5.7's.

The following fuel burns are for later 5.7L engines and were measured on our dynamometer.

At 1000 RPM fuel burn was 1.4 gal / hr

At 3000 RPM fuel burn was 8.4 gal / hr

Using your example the round trip distance is 36 miles. At 6 knots it will take you 5.2 hrs to complete; at 18 knots it will take 1.7 hrs.

At 1000 RPM: 1.4 gal/hr x 5.2 hrs x 2 engines = 14.6 gallons

At 3000 RPM: 8.4 gal/hr x 1.7 hrs x 2 engines = 28.6 gallons

So if time is not an issue the lower speed wins by a factor of 2.

Stu
 
CWMS, thanks for remembering the info I sent you. The numbers below we taken when I first installed my fuel flow meters. They are still fairly accurate. The boat is a a 1988 Carver 3807 with Crusader big blocks. Today they have about 2150 hours on them. Speed is in MPH read from a GPS. I now cruise at about 1500 to 1600 rpm. The 1.3 at 1500 is probably wrong. I probably should be about 1.2 or so.

RPM _ GPH _ SPD _ MPG
1000 _ 4.70 _ 5.90 _ 1.26
1200 _ 4.80 _ 6.90 _ 1.44
1400 _ 6.20 _ 7.90 _ 1.27
1500 _ 6.40 _ 8.30 _ 1.30
1600 _ 7.70 _ 8.60 _ 1.12
1700 _ 8.40 _ 9.10 _ 1.08
1800 _ 9.00 _ 9.30 _ 1.03
1900 _ 10.00 _ 9.70 _ 0.97
2000 _ 11.60 _ 10.00 _ 0.86
2100 _ 12.70 _ 10.40 _ 0.82
2200 _ 14.00 _ 10.50 _ 0.75
2300 _ 15.80 _ 10.80 _ 0.68
2400 _ 18.00 _ 11.20 _ 0.62
2500 _ 19.00 _ 11.30 _ 0.59
2600 _ 21.70 _ 11.70 _ 0.54
2700 _ 22.50 _ 11.50 _ 0.51
2800 _ 28.80 _ 12.60 _ 0.44
2900 _ 29.50 _ 12.70 _ 0.43
3000 _ 36.00 _ 13.70 _ 0.38
3200 _ 40.50 _ 16.30 _ 0.40
3800 _ 51.50 _ 21.70 _ 0.42

Hope this helps
 
That's outstanding - exactly what I was looking for. Thank you VERY much!
 
On my 1986 32 Mariner, on plane at 3200 rpm on a 45 mile round trip, I will burn through 50 gallons. This trip includes several no-wake zones that maybe add up to 6-8 miles. I have crusaders, 270 hp each. Can't remember the size... The trip takes me about 4 hours round trip total.
 
I just found these posts. I also have a 3807 w/454's. My question for Oasis is, Did your 3807 top out at 3800, or was that where you stopped measuring? Mine tops out around 42-4400, though I only do this briefly to test engine/hull condition, and only for seconds at at time, for obvious reason$. I thought the props were 4 blade 24x23, but the prop shop measured them at 24x21.5's. Top end is in mid 20's. I have seen 24, but again, I have never left it at full throttle long enough for it to build up full momentum.
 
idyltimelg,
Your 42-4400 RPM's is just where you want to be for WOT.
 
I understand that my WOT numbers are correct. I guess my thinking is that if Oasis has more prop, he is moving a little faster at lower rpm's, but maybe burning a little more fuel. At 1200, I am moving about 6 (by GPS) on a fresh bottom and new running gear, while Oasis is close to 7. I have to hit 1800 to get 7.5 to 8, where Oasis is at 9.3. Based on Oasis's fuel burn figures, I nearly double the fuel burn to gain 2 mph. What I am hoping is that I have less pitch, so the engines don't have to work as hard for a given rpm, and our actual mpg figures would be similar. It's all a mystery. I would like to have Twinscans, but hate the idea of fishing the wires around and up to the bridge (no lower station on my boat).
 
I don't remember why I stopped at 3800. Maybe I couldn't afford further testing. At one point my boat did about 4200 rpms and if I remember correctly it topped out at about 26 or 27 MPH. The cruising. I have had the boat 9 years and have only had it at WOT a few times. I run it like a trawler and plan my trips accordingly. I just turned over to 2200 hrs and plan on getting a lot more hours out of it. I am currently running four blade props and at 1600 rpm run about 8.5 mph.

Every on have a great thanksgiving. We are going to the boat TDAY evening and going downtown Chattanooga for the lighted boat parade, fireworks and the entire weekend.
 
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