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Old 04-30-2013, 09:35 PM   #1
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Default SPEED : Cruise & Top End -- Fuel Consumption -- 3200 3300 3500 3700 4100 SCR

Hey guys,

I've been doing a bit of research on these. I tried to find some data on specs and real world and came up with no consolidated info. So I thought I'd ask here and update this post with information as I come by it.

So if you have some stats to add I'd appreciate them:

Boat Model
Engines
Drives
Props

Cruise: Speed / RPM / Consumption
Max:Speed / RPM / Consumption
==========================
DATA:

3200 SCR

3300 SCR

3500 SCR

3700 SCR

7.4 MPI: 3200 RPM 20 MPH 30 GPH (William Ferrell)

3900 SCR

4100 SCR
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Old 05-01-2013, 12:27 AM   #2
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1998 37 SCR
7.4 MPI
inboard
Stock
20mph 3200 30gal total per hour
unknown
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Old 05-01-2013, 02:52 PM   #3
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Thanks William... I updated it
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Old 05-02-2013, 01:58 PM   #4
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Oh boy, this is going to be a world of variables unaccounted for here. Wind, Current, Sea State, whether the engine is in tune, how the boat is propped etc. In the case of outdrives, the gear ratio of the drive, the type of drive and how the boat is operated. Two identical boat/engine packages can return very different numbers, if for example, one person trims and tabs differently than the other. How loaded (or overloaded) the boat is will also impact behavior.

What is your ultimate goal here?
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Old 05-03-2013, 12:48 AM   #5
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1998 3700 SCR, 7.4 MPI, 24,000 lbs with full tanks and gear

We cruise slow at 1200 to 1400 rpm on a fresh water lake. I log every weekend's mileage and engine hours. Over the last few months we cruised 190 miles. Last weekend I topped off the tanks with 155 gallons ($4.36 for 87 octane). The left tank took an extra 24 gallons as it also feeds the generator. Assuming the engines burn roughly the same amount of fuel they would have consumed 131 gallons. Our average speed was 5.3 mph at 1.45 gpm (11.15 gph).

1200 rpm - 6.8 (0% tabs)
1400 - 7.7 (0%)
1600 - 8.7 (0%)
1800 - 9.3 (10%)
2000 - 9.9 (20%)
2200 - 10.4 (50%)
2400 - 11.0 (100%)
2600 - 12 (100%)
2800 - 13 (100%)
3000 - 20 (100%) To achieve this speed/rpm and stay on plane I have to accelerate to at least 25 mph then slowly back off.
3200 - 21 (75%)
3400 - 23 (50%)
3600 - 25 (30%)
3800 - 27 (20%)
4000 - 29 (20%)
4200 - 31 (10%)
4400 - 32 (10%)

Based on 24 gallons the Westerbeke 7.2 generator burns .47 gph.
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Old 05-03-2013, 04:10 PM   #6
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Great Info

Shrew, my goal is simple. Data analysis....

While I understand there are unforeseen variables. I think most boat owners take these factors into consideration when quoting their figures. If we get a large enough sampling then we can review data that looks erroneous.

Ultimately, my goal would be to find the correct powerplant / props for each of our missions. Some people might be looking for top end, while others are looking for economy.

If we can't get reasonable data, still no harm done.
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Old 05-04-2013, 12:36 AM   #7
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When you burn at least $150 USD each weekend or take extended voyages, this could be very helpful.

I've yet to launch our '96 3200 on Lake Michigan this year. We have twin 4 bbl 350s w/ B2s and we'll be burning a lot more fuel than we did on the Chain O'Lakes. I've had a Garmin 740S plotter/radar bundle installed with fuel flow sensors in hopes of finding the "sweet spots" in terms of RPM, drive trim and trim tab set ups. A friend with a '94 sister ship says he's always hunting for the damn "sweet spot".

I know, if you want to save a ton of money, sell the boat. I would just like to enjoy cruising knowing that we're not burning a ton more fuel than we have to.

I'm also very curious to see how much more fuel efficient FI is over carbs and if an upgrade to the 3900 or 4100 is going to melt our credit cards at the pumps.
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Old 05-04-2013, 04:12 AM   #8
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Exactly AlwaysSober.....

Let us know what you find out. If your friend isn't a member here maybe you could post his numbers.
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Old 08-17-2017, 01:34 AM   #9
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Quote:
Originally Posted by Fastbri View Post
I recently purchased my 3700 SCR w/twin 454 MPI (310hp Each)
I am at Lake mead about 1100 ft elevation and I can only get 4000 RPM and WOT 23mph.
What props are you running and where?
Welcome aboard

Four year old thread and the OP has not posted since. I suggest you start your own thread.
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