Cat 3116 & 3126 Fuel Burn in 400 & 380

Hellman Huddle

Hellman Huddle

New Member
Nov 6, 2009
510
Lake Wateree/SC Coast
Boat Info
2005 260 Sundancer
2000 F-350 Diesel
Engines
350 Mercruiser Bravo III
Anybody have any fule burn data on these two engines/boats? I am looking at a couple and was wondering what the total fuel was for cruising speed & at trawler speed.

Was considering moving up to a trawler but I have read the fuel burn for these was very reasonable and I like the fact that if I need the speed it is there! BTW, both are Sedan Bridge 2000 & 1999.

Thanks!
 
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The fuel burn for Cat engines is the same rate per hour no matter what the engines are in. The variable is going to be the boat's speed.

At rated cruise rpms of 2400, the 300hp 3116 burns 19.4 gph; the 350hp 3116 burns 22.6 gph, and the 420hp 3126 burns 26.0 gph.
 
At rated cruise rpms of 2400, the 300hp 3116 burns 19.4 gph; the 350hp 3116 burns 22.6 gph, and the 420hp 3126 burns 26.0 gph.

That's pretty much what I get with my 400DA running the 350 HP Cats.
 
my boat burns more fuel that what Frank listed. If you take out 1 gallon per hour for the genset, I'm at about 28-29 GPH at cruise (both engines). At 9 knots (1400 RPM), I'm about 9 GPH (both)
 
You have to mathematically interpolate the Cat published tables for speeds below 1600 rpm so I'm not going to go to the trouble until you figure out what engines and what boat you are buying. I can tell you that 1500 rpm seems to be a sweet spot for the 3116/3126 and that is 6.0 gph and 9.7 kts for me. I think 1200 is too slow and will give you some performance and maintenance problems, but is going to net about 4.0 gph for 350 hp 3116's.
 
I found some spec sheets on the internet and found:

3116 300HP Burns around 2.3 gph @ 1400 rpms
350HP ..................2.5 .......................

For a grand total of around 5gph. I agree each boat has their sweet spot. But, all of this info is very encouraging considering I was looking at some 320-360's with gas engines that burn a whole lot more. I just want to make sure I can afford to operate after making a purchase.

Definitely a choice to make between a 380/400 Sedan Bridge versus a trawler. Thanks
for the info all! :smt038
 
fwebster said:
I can tell you that 1500 rpm seems to be a sweet spot for the 3116/3126 and that is 6.0 gph and 9.7 kts for me. I think 1200 is too slow and will give you some performance and maintenance problems, but is going to net about 4.0 gph for 350 hp 3116's.
Click to expand...

At 1500 rpm I leave a huge wake; not a problem offshore but up here in 1000 Islands it will give you a lousy reputation quickly. 1200rpm puts me just on hull speed with a reasonable wake. Frank, I appreciate that running at that speed continually is not a good idea but what performance problems are you referring to?

PS I just had my props tuned to Class S so I am looking forward to replotting my RPM to Speed graph!
 
There aren't any serious problems............ these engines like enough rpms that the turbo is creating some intake vacuum. At slow rpms you may get an oil drop or 2 where the hump hose from the breather connects to the turbo housing if you have Walker AirSeps; drips into the bilge under the breather pipe if you don't.

I've only had it happen once and that was during the oil spill last summer when the clean up crews were working in the Gulf access/port entrance washing off boats and everyone had to maintain idle speed as we transited the area. I usually run between 1000 and 1500 rpm in high traffic areas and don't have any problems.

There is no mechanical reason the engines can't run 1200 rpm, its just that you might get some oil drips in the bilge.
 
Thanks. BTW I am very pleased with the Class S props. They were expensive but I will get it back in fuel.
 
Hi... did some experimenting this summer on our summer vacation in North Channel area with trawler speed and normal 2400rpm cruising.....
1350 would work out between 9.5 and 10 mph depending on water conditions....on one tank for a 20 mile trip(and other similar legs) we travelled 10 miles at TS and rest on plane and gph worked out to 9gph.... also checked a 60 mile trip on plane the whole way and gph worked out to be 18.3gph(imperial gallons + 20% for US Gal).
Admiral doesn't like trawler speed when there's much wave action, me either.... nice to have option to save a little fuel and enjoy the scenery or travel normal cruise speeds... our 380 mile trip cost 650 bucks with 3/8 tank back home
 
Hellman Huddle said:
....Was considering moving up to a trawler but I have read the fuel burn for these was very reasonable and I like the fact that if I need the speed it is there! BTW, both are Sedan Bridge 2000 & 1999. .....
Click to expand...

Just keep in mind that the fuel burn tables show you GPH, which may sound very reasonable. However, the numbers that you're mostly interest in are MPG. This is where you'll pay much more when comparing DB to DA with the same engines.

An exapmple, most DB owners I've talked to said the true AVG number is .6MPG at cruising speed. DA owners get 1.0MPG or in some cases even better. So, before you spend any money make sure you have your expectation set properly. There's a huge difference between DB and DA, but you pay for it twice (during purchase and every day use).

If you get the DB b/c it can cruise at 10MPH and give you great fuel economy, it might get very old very fast and you'll be at the normal crusing speed most of the time. Everyone is different, some people have the time and trully enjoy slow cruise even when travelling long distance. So, know how you will use your boat and look at both sides of the coin.

Good luck,
Alex.

Hellman Huddle said:
They call it an Aft Cabin, but looks very similiar to a Sedan Bridge.
Click to expand...


But, you're still looking at apples and oranges. These are very different boats in many ways.
 
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Alex,
I agree! I was seriously looking at trawlers and understand the speed, but if I can get a DB that gets close to the fuel economy at trawler speed that would be great. I like having the speed available if needed to outrun a storm or get somewhere faster if needed. On a daily basis I would be at trawler speed. The SD is too much like a cave and are not built for living on board as I would prefer, and I don't think they do well at trawler speed.
 
I'm still confused about how an aft cabin looks like a sedan bridge.

At 1000 RPM, I'm doing 8 kts and burning 4 GPH. At 1300, I'm climbing a hill and not gaining any speed. At 2400, I'm burning 26-27 GPH.
 
I've been cruising at 1500 rpms as per Frank's recommendation and it's not bad. I'm doing about 10kts, kick it on autopilot and enjoy cruising all day sipping fuel. 1500 is definitely a sweet spot on the 450, the boat is flat, i'm not digging a big hole, and it's a surprisingly stable ride. If i'm not in a rush, this is my preferred cruising speed now. No idea what i'm burning but it is less than planning cruise for the same distance. I like it because I can kick back, relax, enjoy the scenery, eat something, play a game, whatever. Set some radar perimeter alarms and i'm good to go.
 
FWIW the fuel economy I get is given in the graph I made below. The fuel consumption is theoretical, kindly provided by Frank, the speeds were measured, two way, last weekend. I didn't bother measuring the "plowing" speeds between 11 and 17 knots as I never operate there - I simply interpolated them. Props are ISO 484 Class S. I am setting up this boat as a live-aboard Great Loop boat for our retirement in a couple of years. Fuel should not be a problem in my opinion.

View attachment 21181
 
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