Fuel Burn of Twin Suzuki DF300’s on a 28 Foot Fiberglass Boat

Sharphooks

Sharphooks

Well-Known Member
Anybody running twin Suzuki 300’s? I’m curious what normal fuel burn would expected to be on a boat with a total weight of approx. 14,500 running at cruise speed

I just took delivery of my new ride yesterday and I couldn’t get much better then 2.25km/3.78 liters (1.4 miles/gallon)

The disappointing part of maiden voyage at that fuel burn rate: zero weight in the boat and only 1/4 tank of gas

Curious what other guys are getting with that boat/motor profile
 
GpH is the best thing to go off of when dealing with this. Imo. Also any 300 hp modern outboard will burn 10 or 11 GPH at around 4 grand. You can give or take a little bit with prop choice and engine choice but it's all in that park.
 
Sharphooks said:
Anybody running twin Suzuki 300’s? I’m curious what normal fuel burn would expected to be on a boat with a total weight of approx. 14,500 running at cruise speed

I just took delivery of my new ride yesterday and I couldn’t get much better then 2.25km/3.78 liters (1.4 miles/gallon)

The disappointing part of maiden voyage at that fuel burn rate: zero weight in the boat and only 1/4 tank of gas

Curious what other guys are getting with that boat/motor profile
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I thought you just got a new Seaport 28 last year?
you could try diesel. 2.3 mpg on a 16000 pound boat. 😀

your calculation is in US gallons too. 4.54 litres per imperial gallon.
 
For 14500lbs boat that sounds about right. We are a few thousand pounds less when unloaded, and run at roughly the same specs when we are loaded. Twin 300 Yamaha, not Suzuki, but shouldn’t be far off.

Did you get the DuoProp?

Wish the Yamahas ran on diesel…

Anyone know what gallons the motor companies are typically providing their numbers in? Imperial or US? 4.5 vs 3.8 is quite a spread. Hope I’m burning US gallons…
 
The calculations the outboard guys use is a US gallon (3.78 liters)

No, I didn’t get the duo-props....I was warned away from them....I heard the 30” legs are having issues with shaft seals etc so I stuck with the tried and true old-school Suzukis

Just for grins, I made a telephone appointment with Sharrow this morning.

Reason: if I got 1.4 MPG with half a tank of gas and zero weight in the boat (as in nothing on the boat except chartplotters and a roll of toilet paper) I know those numbers are going off a cliff as soon as I top off the gas, put fresh water in the tanks, and start adding downrigger balls and gear

IT’ll be interesting to hear what Sharrow says Based on the boat config I have
 
I don’t think you’re going to get much better than that unfortunately.
I’ve got about 15 hours on my Merc 250 (approx 4500lb boat decently loaded) so you’re gonna be double me at least. I don’t think there much differences these days between manufacturers. I’m kind of a dork so I been tracking it pretty close. Here’s what I get so far:

-2.4 nautical miles (2.7miles) per gallon
-9.5 g/hr approx
This is at cruising speed of 25-30knots, 4000-4500rpm. When I open it up to 5500-6000 I can get 40+ knots but the gas mileage efficiency drops right off (like over 13g/hr). Using 3.78L/gal which is most common I think.
 
That’s sounds like you are in the right ballpark but you might be able to eke out a few marginal gains for another 0.1 - 0.3 MPG.

We have a 30’ Pursuit with twin Mercury I6 Verados. Dry weight of the boat without engines is about 10,000 lbs, so plus engines, full fuel (310 G), water (30 G) and gear, we are probably around your current weight. I get 1.3 - 1.4 when the tanks are full and will see a bit better once about 50 G of fuel has burned off (and even better once under 1/3 a tank).

Did you check you were in the right RPM range for the props currently installed? I propped mine for when the boat is full so the engines aren’t working too hard when we are fully loaded up and staying on the boat for a couple weeks. Manufacturers/ dealers are notorious for over-propping boats so the test results look good when they are lightly loaded.

You could also try a different brand of props. The ECO Enertias are known to get better mid-range cruising than most. I’ve posted my views on the Sharrow props before, so won’t repeat them again other than to say I’m very sceptical of their claims.

You’ll probably get a bit better mileage as well once you sort out the nuances of trimming the new boat optimally. My first impression was that 4,500 RPM sounds like it is in the high side of where you want to be, especially given you were running “light”. I’ve found we generally get the best cruise at 4,100 - 4,300 RPM depending on how heavy the boat is; the previous F250’s in the boat did better at 3,900 - 4,200 RPM.
 
I found my new Yamaha F250 got better mileage post break-in period. Not sure if your motors are new or not.
 
CBsqrd said:
That’s sounds like you are in the right ballpark but you might be able to eke out a few marginal gains for another 0.1 - 0.3 MPG.

We have a 30’ Pursuit with twin Mercury I6 Verados. Dry weight of the boat without engines is about 10,000 lbs, so plus engines, full fuel (310 G), water (30 G) and gear, we are probably around your current weight. I get 1.3 - 1.4 when the tanks are full and will see a bit better once about 50 G of fuel has burned off (and even better once under 1/3 a tank).

Did you check you were in the right RPM range for the props currently installed? I propped mine for when the boat is full so the engines aren’t working too hard when we are fully loaded up and staying on the boat for a couple weeks. Manufacturers/ dealers are notorious for over-propping boats so the test results look good when they are lightly loaded.

You could also try a different brand of props. The ECO Enertias are known to get better mid-range cruising than most. I’ve posted my views on the Sharrow props before, so won’t repeat them again other than to say I’m very sceptical of their claims.

You’ll probably get a bit better mileage as well once you sort out the nuances of trimming the new boat optimally. My first impression was that 4,500 RPM sounds like it is in the high side of where you want to be, especially given you were running “light”. I’ve found we generally get the best cruise at 4,100 - 4,300 RPM depending on how heavy the boat is; the previous F250’s in the boat did better at 3,900 - 4,200 RPM.
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That’s very helpful info, CB—-your Pursuit spex match the hull weight fo my Commander with exactly the same tank sizes for fuel/water so good boat for comparison purposes

My twin Suzuki DF300’s are propped with 16x18.5” Suzuki props. I had a single DF300 on an earlier boat and after numerous prop tests (including 4-blades) I ended up sticking with the 16x18.5” 3-blade so I wasn’t surprised to find the same pitched props on the twins I own now.

Meanwhile, I bought the boat pre-owned so the twin DF300’s already have 100 hours on them—-they are definitely broken in.

I know your take on Sharrows...but I did talk to them this morning and they said with the hull profile of my Seasport, they felt that minimum 20% increase in efficiency in the mid-range would be in the cards....I’m at least listening to them because I would love to see that Commander cruise at 3,000 - 3,200 and not fall back into a hole the way it does now (a Yamaha T25 hanging off the stern doesn’t help)
 
Sharphooks said:
That’s very helpful info, CB—-your Pursuit spex match the hull weight fo my Commander with exactly the same tank sizes for fuel/water so good boat for comparison purposes

My twin Suzuki DF300’s are propped with 16x18.5” Suzuki props. I had a single DF300 on an earlier boat and after numerous prop tests (including 4-blades) I ended up sticking with the 16x18.5” 3-blade so I wasn’t surprised to find the same pitched props on the twins I own now.

Meanwhile, I bought the boat pre-owned so the twin DF300’s already have 100 hours on them—-they are definitely broken in.

I know your take on Sharrows...but I did talk to them this morning and they said with the hull profile of my Seasport, they felt that minimum 20% increase in efficiency in the mid-range would be in the cards....I’m at least listening to them because I would love to see that Commander cruise at 3,000 - 3,200 and not fall back into a hole the way it does now (a Yamaha T25 hanging off the stern doesn’t help)
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I hope you try and it works out I’m still curious
 
Would be curious to know what your numbers are and what your wot rpm is with those 18.5p props. The big zuki's are notoriously hard to prop with the big wheel they use. With my 300 I was only able to get to about 5500 rpm with the zuk 16x18.5 prop. When i dropped to their next prop the 17 pitch i was able to get to about 5800 rpm wot but i lost a bit of fuel economy. I know the eco enerita props are better but at $1700 a prop now thats alot of gas money for a .2-.4 mpg increase in fuel economy. I ended up sticking with the 17p as it gave better holeshot and throttle response.
 
Sharphooks said:
That’s very helpful info, CB—-your Pursuit spex match the hull weight fo my Commander with exactly the same tank sizes for fuel/water so good boat for comparison purposes

My twin Suzuki DF300’s are propped with 16x18.5” Suzuki props. I had a single DF300 on an earlier boat and after numerous prop tests (including 4-blades) I ended up sticking with the 16x18.5” 3-blade so I wasn’t surprised to find the same pitched props on the twins I own now.

Meanwhile, I bought the boat pre-owned so the twin DF300’s already have 100 hours on them—-they are definitely broken in.

I know your take on Sharrows...but I did talk to them this morning and they said with the hull profile of my Seasport, they felt that minimum 20% increase in efficiency in the mid-range would be in the cards....I’m at least listening to them because I would love to see that Commander cruise at 3,000 - 3,200 and not fall back into a hole the way it does now (a Yamaha T25 hanging off the stern doesn’t help)
Click to expand...
Back to this again I see. You know the reason that cruising at 3000 rpm is generally not a good idea? The engine isn't making power. Outboards like to sing. The are not singing at 3 grand. Unless your waaay over powered.
 
ship happens said:
Back to this again I see. You know the reason that cruising at 3000 rpm is generally not a good idea? The engine isn't making power. Outboards like to sing. The are not singing at 3 grand. Unless your waaay over powered.
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So true, plowing water is much harder on the motor than singing at 4000rpm
 
Reel Time said:
So true, plowing water is much harder on the motor than singing at 4000rpm
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Well the whole claim with the sharrows is that you're not plowing water at those rpms. They provide more lift and thrust at lower rpms, aledgedly.
 
Unreel said:
Would be curious to know what your numbers are and what your wot rpm is with those 18.5p props. The big zuki's are notoriously hard to prop with the big wheel they use. With my 300 I was only able to get to about 5500 rpm with the zuk 16x18.5 prop. When i dropped to their next prop the 17 pitch i was able to get to about 5800 rpm wot but i lost a bit of fuel economy. I know the eco enerita props are better but at $1700 a prop now thats alot of gas money for a .2-.4 mpg increase in fuel economy. I ended up sticking with the 17p as it gave better holeshot and throttle response.
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$1200 cdn currently at retail
 
I have a Pursuit with twin 300 suzks. When full with fuel and gear I'm just over 12000 lbs. I have 16in diameter 17 pitch props. Cruising speed around 28 to 30 mph, at 18.5 to 20 gallons an hr. I get around 1.1 to 1.4 miles per gallon. The more I trim up the better. I've put almost every type of prop on it last year to see what i could gain. Lots of different issues. I can PM you my number and you can give me a call if you want.
 
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