Cat 3116 & 3126 Fuel Burn in 400 & 380

[Turtlesboat]

That's a great chart.

 

[Boat Drinks]

I'm looking for some more information regarding the maintenance and performance issues Frank W referenced on the last page. We have a 400 DA with 3116 350 engines with about 1030 hours, always in fresh water. 1000 hour maintenance all taken care of at the end of last season. We are about 2-3 years from retiring and heading from WI to FL to shop for a sailing catamaran and hopefully head to the Caribbean. Our preferred way of getting to FL would be the midwest route of the Great Loop. One of my concerns is fuel consumption on the journey. I would like to take it slow most o the way, but don't want to do any damage to the engines by not running at high enough RPM's.

Would running consistently between 800-1000 RPM's cause damage to the engines? And I so would bumping the RPM's to 1500 or 15 mins or so an hour help protect the engines? Based on what we have been reading about the route we are looking at averaging about 60-80 miles/day, so the engines would be running 6-8 hours/day I we are cruising at around 10MPH.

Any insight would be appreciated.

Thanks,

Mike

 

[Steve S]

I'm looking for some more information regarding the maintenance and performance issues Frank W referenced on the last page. We have a 400 DA with 3116 350 engines with about 1030 hours, always in fresh water. 1000 hour maintenance all taken care of at the end of last season. We are about 2-3 years from retiring and heading from WI to FL to shop for a sailing catamaran and hopefully head to the Caribbean. Our preferred way of getting to FL would be the midwest route of the Great Loop. One of my concerns is fuel consumption on the journey. I would like to take it slow most o the way, but don't want to do any damage to the engines by not running at high enough RPM's.

Would running consistently between 800-1000 RPM's cause damage to the engines? And I so would bumping the RPM's to 1500 or 15 mins or so an hour help protect the engines? Based on what we have been reading about the route we are looking at averaging about 60-80 miles/day, so the engines would be running 6-8 hours/day I we are cruising at around 10MPH.

Any insight would be appreciated.

Thanks,

Mike

Mike,

As Frank stated...

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.
--------------------------------
Now one other minor issue might surface. I ran about 1200 RPM on a 2 hour cruise and got a lot of soot on my transom, so I avoid that RPM now.

On another note - if you are planing on your trip in 2020 you may have some difficulties as the locks on the IL River will be closed for rebuilding for a good part of the summer. See the link for more info. https://www.mvr.usace.army.mil/Missions/Navigation/Navigation-Status/

You might want to join the AGLCA "Americas Great Loop Cruising Association" at greatloop.org

 

[Riptide III]

I think I baby my engine! I run 2200 to 2250 RPMs. I would like to run at 2400 but thought it seemed high. What do you all run again?

 

[Steve S]

I think I baby my engine! I run 2200 to 2250 RPMs. I would like to run at 2400 but thought it seemed high. What do you all run again?

I normally run @ 2,400 RPM. I have also run at 2,200 RPM. I haven't really run at a cocktail speed yet....

 

[yobub]

Cat 3116's 350hp I usually run at 2400 rpms. 400DA.

Occasionally I will run at displacement speed, but only for 15 min or so heading to a nearby beach.

 

[Boat Drinks]

Thanks or the reply's. I will play around with different RPM's over the next couple years and see what gets us the best fuel consumption on longer runs.

We typically cruise between 2200-2300 RPM's on the lake we are currently on and that seems to work pretty well or us. However I don't want to burn that much fuel on the way down to FL.

We are aware o the Chicago river closures in 2020, the earliest we will be able to make the move is Aug. 2021. Hopefully the construction will be done by that time.

 

[Steve S]

We typically cruise between 2200-2300 RPM's on the lake we are currently on and that seems to work pretty well or us. However I don't want to burn that much fuel on the way down to FL.

Another thing to consider, Heading south you will be going most of the way with the river flow. So you will pick up 5-7 knots in addition to whatever speed you are producing. The exact speed will be dependent on the actual river flow.

Also many locations will be "no wake" zones.

Carter Chapman can give you details on the southern portion of the route as he travels from Chattanooga TN to the FT Myers FL area yearly.

 

[dtfeld]

I have been running a lot at 900-1000 rpm most of the year due to a transmission issue, and occasionally pushing it up to 2200-2400. 2325 seams to be my sweet spot. Haven’t noticed any downside other than the gas gauge has barely moved this year.

Over in the 400/410 thread there was recently a discussion about fuel consumption. Several 410 DA owners w/ 3126’s are calculating about 1 nm/gallon at cruise speeds 2200-2400 rpm. At 1000 rpm, my 410 does 7.2-7.5 kits and burns maybe 3-4 gals/hr, so I estimate 2+ nm/gal. Nobody has fuel flow gauges so these are estimated based on the CAT fuel consumption charts and observed speeds. Secondarily, these burns can be confirmed at the fuel pump if you keep track of your distance traveled and from all indications, these numbers are fairly accurate. Certainly good enough for fuel planning purposes given an ample reserve fuel.

 

[The Bill Collector]

Our marina is down a no wake waterway... It's 15 minutes in&out at dead idle, it's perfect for warming up and cooling down. While underway it's 2000-2400 depending sea condition and schedule.

 

[JVM225]

I think I baby my engine! I run 2200 to 2250 RPMs. I would like to run at 2400 but thought it seemed high. What do you all run again?

2400 for my 3126’s.
I went to a Cat Marine engine maintenance seminar in March at the local CAT dealer The guy giving the class has more than 50 years experience and his recommendation for recreational boaters is run them at 2400. He said they like to be worked and that running them at less isn’t doing them any favors.
That’s pretty much what the manual says to do too.
Having diddly squat diesel experience before this boat, I have to do what the experts say.
When I have to run at idle speed (no wake zones, etc.) I’ve found that idle speed (no throttle at all) works best. Impossible to keep to 5 mph at idle speed. In my own canal which is narrower, or other narrow places I usually have to take them in and out of gear to abide by no wake and avoid rocking boats tied to the bulkheads on either side.
Never usually have the need to run them at 1000-1200 so I can’t provide feedback on that.

 

[Oh Brian]

Our marina is down a no wake waterway... It's 15 minutes in&out at dead idle, it's perfect for warming up and cooling down. While underway it's 2000-2400 depending sea condition and schedule.

+1

 

[Bartlett Bob]

I was looking forward to reviewing your graph but the club returns an erro attachment cannot be found when I click on the link??