Click for Ocean Alexander Click for Burger Click for Westport Click for Mag Bay Click for Walker

What is fuel consumtion for CAT 3126-420hp?

Discussion in 'Cabo Yacht' started by Todosjohn07, Sep 21, 2013.

You need to be registered and signed in to view this content.
  1. Todosjohn07

    Todosjohn07 New Member

    Joined:
    Sep 21, 2013
    Messages:
    3
    Location:
    Cabo San Lucas
    i have a 2003 3100 Cabo Express with twin CAT 3126TA's. looking for info on what the fuel consumption might be at very low ( idle) speeds. cut sheet from factory doesn't go that low. trying to make a 430 mile leg with 350 gallons and don't want to go out and do expensive sea trial at those speeds.:)
  2. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    At 7 knots or keeping the motors at or under 1000 rpms, you'll easily get 2 mpg.
  3. Todosjohn07

    Todosjohn07 New Member

    Joined:
    Sep 21, 2013
    Messages:
    3
    Location:
    Cabo San Lucas
    thanks mucho! i hope that works out.
  4. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    I ran a 45' Searay SB with the same motors all of the way to St. Croix from Ft. Lauderdale mainly at 7.5 knots (hull speed), we were able to do those distances no problem at 7.5 knots.....I think cruise was 2400rpms, if you keep them at 1200rpms or below you'll save a ton of fuel. 1000 rpms even less fuel. I ran them up to cruise every 6 hours for 20 minutes. You can also bring 2-50 gallon drums for extra measure, and your boat should have a fuel fill on the top of the tank to make it easy to get it in there.....I'd leave and stay at 1000 rpms (or less if you're pushing past hull speed at that rpm), keep it there for 10 hours, run it up to cruise for 20 mins 1 time and see how much of a drum you can stick in the tank, then you'll know your exact consumption. I would definately bring 2 55 gallon drums, and get those into the main tank when you can.
  5. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    The condition of your engines, the tuning, the weight of your boat and cargo can all play a role. You say you don't want to do an expensive sea trial but I sure wouldn't gamble without some real current information from actual experience with those engines on that specific boat. I wouldn't even use manufacturer's numbers. We all need to know the true consumption of our boats. We learn that either through experience such as starting full, going a distance, refilling and calculating or through the use of test or measuring equipment, but I personally am not going to undertake a distance I'm not sure of with some allowance for winds and tides as well. The other issue that comes into play is knowing whether you truly have the stated amount of fuel usable, especially on an older boat. Where is your fuel pickup in the tank or tanks. If unsure, I'd do just as Capt J said and take additional fuel until I knew for certain.
  6. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    Unless you really overload a boat or get the balance way wrong, hull speed will pretty much be the same at a given rpm within 5%. I'd do 7 knots and keep it at or under 1000 rpms with 2-55 gallon drums as far foward as possible and go. I have done at least 50 long long leg deliveries this way, and spending a day seatrialing and wasting time and fuel was not an option........
  7. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    I agree with what you've written and certainly believe your approach makes even more sense in a delivery situation where you don't have luxury of time and learning. However, I would as an owner want to know more about my boat and have more information, not just for the one trip but ongoing. Now part of that can be obtained on the trip doing it as you've suggested. Your vast experience in loading, balance, being sure the engine is operating properly, knowing the hull condition is not such as to significantly impact things, is very important and aids you.

    I do have a question for you, Capt J. In your experiences have you encountered situations where tank capacity was not as stated and/or where the tank and fuel pick up were designed in such a way as to not access the full capacity? I knew someone recently to encounter such a problem and just wondered how common or rare it was in your experience.
  8. Fishtigua

    Fishtigua Senior Member

    Joined:
    Jul 20, 2007
    Messages:
    2,937
    Location:
    Guernsey/Antigua
    On the run down to Venezuela from Miami on the Bertram we used a lot of bladder tanks on the aftdeck. At each refuel along the way, at a pace a bit faster than 7.5 knots, these tanks paid for themselves in safety and Get Go in case of very bad weather. (We had a fair bit of that).

    Have a look and a think.

    http://atlinc.com/pdfs/PillowTanks/DS617-REB-Fuel-Bladders-web.pdf
  9. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    What are the advantages both ways of drums vs. bladders?
  10. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    I'm not Capt J, but I hope you don't mind if I chime in here;
    Our aft tank is formed to follow the hull (Bert 58 my). It goes deeper as the long tank goes forward. Pick up in the aft end. Fuel sender mid way. I managed another boat that did the same thing (Striker 44).
    So, with bow down or level, if you go bingo on these tanks, another large part of your fuel is in the tank.
    So, our aft tank is 550 gallons, I'd say 475 or less is usable with bow down. The sad part, that remaining fuel is where my fuel snot is lurking. When I pick the bow up (when I feel rich) the filters clog.
    My gen-sets draw from the front of this tank. At anchor, they clog also. Front tank only for them.

    Next thought, fuel tank pick up tubes are rather crude. Just a length of copper tube soldered to a top fitting. Sometimes there is a screen of some kind on the end. I have worked on boats where the pick up is on the bottom of the tank, and others 6 inches from the bottom (made with scrap pieces). If your concerned, pop the plate and measure it to make sure your close to the bottom. If you use the boat allot, put the pick up low, if it's a dock queen, maybe not so low.
  11. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    That was my concern that until you know the true range of your boat, you must be extra conservative. I had an acquaintance who recently found out the hard way. He purchased a boat and one of the first things he had added was a monitor for usage so he could find his best areas for fuel usage. He was so sure of himself and his usage that he decided quite unnecessarily to not refuel between Fernandina and Fort Lauderdale. Needless to say he got towed in and he was furious at the fuel usage meter. He had a 500 gallon tank and he felt like he should have 80 gallons left. Well, he was refilled at the marina and it only took 425 gallons. Now he was one who purchased with no survey, didn't get anything checked out after purchase, just added gadgets. I didn't know if his case was very rare or how often such issues were encountered.
  12. Todosjohn07

    Todosjohn07 New Member

    Joined:
    Sep 21, 2013
    Messages:
    3
    Location:
    Cabo San Lucas
    thanks to all. i AM going to do a sea trial. first one at 2000 rpm since CABO says that's the sweet spot. that will tell me how far i can go at gitty up ( about 22 knts)... no matter what i will take empty drums. my first leg is only 140 miles and i can putter down at 900 rpm. next leg is 282.
    the factory says i hold 350. the first month i owned the boat the gauge said 1/3 rd tank. i filled up and took 360! even then teh fuel filters remained clean. as we say in Todos Santos, nos vemos!
    :D
  13. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    Well at least you know you hold at least 360.
  14. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    I can not remember any purchase survey checking fuel pick up / fuel level gages / usable fuel / stated fuel capacity / fuel tank design.
    If the owner added fuel flow equipment and did not calibrate flow vs bingo, then the surprise is on only him.

    Once you go bingo, you know and respect your limits. Till you go there, your still guessing.

    Been there, lost my shirt. Became a better boater.

    Now I'll tell you, I have also run aground. If you tell anybody, I'll have to raspberry you...
  15. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    I used the lack of survey only in conjunction that he just isn't one to be thorough or careful on any aspects, such as checking bingo as your refer to it. As to running aground, I haven't yet, but I know I will. Main reason I haven't is my runs to new areas have been with experienced Captains either running the boat or supervising me. I can't imagine with all the shoaling now that anyone could run the ICW and surrounding areas regularly and never get bottom. Now they might be fortunate enough not to go totally aground. As funding is short it gets more difficult.

    In lake boating, I said I'd never run out of fuel but I did once. I was too lazy to fill Sunday evening and when I went out midweek, the Marina closed at 5 and I arrived at 5:15. I had to adjust to doing things much differently on the lake than I do in the car. Car guages are very accurate and I can tell you what I have down to probably a half gallon. I never fill my car until I'm down to the fuel warning light. On the water you don't know when the marina will be closed or out of fuel or what else will happen. Plus if you don't use your boat often you encounter the risks associated with the tanks sitting near empty.
  16. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    When I do range calculations I figure them based upon 80% of the tanks capacity, always. Always figure that 10% of the tanks capacity is unusable. You will never pull 500 gallons out of a 500 gallon tank. And I also take a look and see what section of the tank the pickup is at, but as in rcrapps boat and a lot of the older Hatteras MY's, one tank will have the pickup near the front of the tank. I also almost always calculate my range based upon GPH/80% of the tanks capacity x speed.
  17. Fishtigua

    Fishtigua Senior Member

    Joined:
    Jul 20, 2007
    Messages:
    2,937
    Location:
    Guernsey/Antigua
    Yep, I hope all skippers do that.
  18. olderboater

    olderboater Senior Member

    Joined:
    Sep 2, 2013
    Messages:
    7,132
    Location:
    Fort Lauderdale
    Another reason to take the manufacturer's range numbers and the numbers of many boat review sites with a grain of salt as they are generally based on 90% and also in ideal conditions with a light to medium load.