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Thread: diesel inboard motor

  1. #1

    Default diesel inboard motor

    what is the most efficient brand of marine diesel?Who gets the best fuel mileage?who is the most dependable?About 30' aluminum so say 400-500 horse.

  2. #2
    Member anonymous1's Avatar
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    Default tough question

    Man thats a tough question with out more information. My guess with that size boat and 400 - 500 hp your plannin on scootin right along. Engine weight per HP is gonna be a factor to consider. Check out the new Yanmar line

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    I would have to say Volvo d-6. I have a 370 h.p. in a BAMF 29 Fish-Around (33' x 9.6' oal). The Boat weighs 12,500 lbs fully loaded. I'm getting about 3 MPG , 12 GPH at 30 knots. The Engine is smooth and quite. I'm think a 400-500 H.P. is a little to much for a 30' and wouldn't expect getting any better fuel economy. You'd be better off with a Volvo. The Drive are much improved from the first DPH. Better gears and bushings. If your dead set on a huge diesel I'd go Cummins QSB.

  4. #4

    Default

    I have a 30 foot aluminum boat with dual, Volvo, D4 225s. I still have to get with Volvo to reprogram the computers so I can trim the drives, but I should get just over 40mph. With them trimmed all the way down, I'm topping out in the high 30s. They only have a couple of hours on them so I don't have any fuel numbers but I will post them once things are straightened out. I figure my drives should last a while since they are the same ones used with the D6 370.

    What builder are you considering?

  5. #5
    Member jrogers's Avatar
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    Default

    I have a Volvo Penta D6-370 in a 31' aluminum boat, and I get 3.1 mpg at 26 kts. Top speed is around 38kts. I don't know that the big difference in mileage will be due to the brand of motor you get, but more from the hull design. The deeper V designs take more power and fuel, but give a softer ride. Also, HP is only part of the story. My 370HP motor also makes something like 650 ft-lbs of torque, whereas with gas motors the torquie is not that great for the same HP rating. My weight with no gear but full fuel and water was 12,000 lbs.
    2009 Seawolf 31'
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  6. #6
    Member captaindd's Avatar
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    Default Volvo D-6

    I am running twin 310 hp Volvo Diesels estimated boat weight empty 16000lbs loaded with fuel, water, gear, and six passengers estimate 20000. Top end 36.5 Knots with G-5 prop cruise at 3000 rpm is around 30knots fuel about 1.46 miles per gallon. I have about 1600 hours on my engines. So far have lost one outdrive shifter, 1 hi pressure fuel pump, and corrossion mess up one outdrive up and down switch. If you have a volvo with out drives spray the electrical connectors with corrossion block. The fuel pump I got a used one from in demand marine in Homer for $700. The shifter from Coastal Marine in Seattle. These new volvo engines are not bullet proof. The are 4 in Valdez and two have been replaced at just over 2300 hours. The piston blocks are not sleaved so you end up buying a whole block if something goes wrong. I recommend out boards for boats that are under 32 feet long and 12000 pounds.

  7. #7
    Sponsor potbuilder's Avatar
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    Quote Originally Posted by captaindd View Post
    I am running twin 310 hp Volvo Diesels estimated boat weight empty 16000lbs loaded with fuel, water, gear, and six passengers estimate 20000. Top end 36.5 Knots with G-5 prop cruise at 3000 rpm is around 30knots fuel about 1.46 miles per gallon. I have about 1600 hours on my engines. So far have lost one outdrive shifter, 1 hi pressure fuel pump, and corrossion mess up one outdrive up and down switch. If you have a volvo with out drives spray the electrical connectors with corrossion block. The fuel pump I got a used one from in demand marine in Homer for $700. The shifter from Coastal Marine in Seattle. These new volvo engines are not bullet proof. The are 4 in Valdez and two have been replaced at just over 2300 hours. The piston blocks are not sleaved so you end up buying a whole block if something goes wrong. I recommend out boards for boats that are under 32 feet long and 12000 pounds.
    Sounds to me like the D-6's have their problems, i spoke with a guy who charters out of whittier at the wasilla outdoors show over this last weekend and the boat he runs also has those engines, yup blew a jug and now he's got a throw away block, that doesn't say much for volvo engineering ??? why not make it a sleaved block so a rebuild is possible.
    I also have a good friend who has a D-6 in his bowpicker and he's had problems with the electronic shifting system.
    Why can't they make a simple shift system that you can troubleshoot(without a laptop) that can be fixed with simple parts ??? Now i really want another lobstah' boat, big power, big rudder, big shaft, big transmission and no troubles.

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    Go to boatdiesel.com for all kinds of info on diesels. The $25/yr is worth it for the support if you burn oil.

  9. #9
    Member tzieli22's Avatar
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    Default Wow, thats a lot of juice for a 30'

    I am running twin TAMD 31P's @ 150 HP each, now don't get me wrong, I would love 200/250 HP's but have to say I am very pleased with my Volvo's. I am cruising at 20knts @ 3200rpm's and get about 1.4 gpm and can push them up to 28knts but will need a fuel stop at Cap Res... . And I am pushing about 14k -16k lbs wet.

    And as some of the others say, depends on what your using it for. If I were going to run a 30' to 32' GC (or the like) I would more than likely run 2 250 yammies. One brakes, you lift it off and replace it in less than an hour. Never going to do that with a Diesel IB. Plus you should be looking for 26 to 30 knots for your cruising speed if you can afford it

    But then again, there is nothing finer than the smell of diesel in the morning...

    Good luck.
    Tony

  10. #10
    Member AK NIMROD's Avatar
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    The 34 FOOTER i sold has twin yanmars ? 230hp each it is getting about 7gph (combined) at 21-22 knots. hard to beat that.
    RETIRED U.S.A.F. CAPT.; LIFETIME MEMBER NRA; LIFETIME MEMBER ALASKA BOWHUNTER ASSOC.
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  11. #11
    Charterboat Operator kodiakcombo's Avatar
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    Default hours per year?

    If you only put seasonal use on your boat you should have outboards, if you run year round I would go with a diesel. I run a 24XL coho I purchased new in 1995, it has a cerified lenght of 26ft. THe boat is on its 6th engine, Volvo gas, volvo AD41, Merc 4.2 d-tronic, Merc 4.2 d- tronic, Yanmar 315, Currenly a Volvo D-4 225.

    THe volvo AD41P had the most hours and was running when I replaced it(5700) planed with 3300# of cod.
    The mercs only lasted 1200hrs.
    THe yanmar had 4000hrs and was running strong when sold.
    The D-4 225 is still going with 1700hrs

    The AD41 had the best milage but was also the slowest 18knts cruise 28 WFO.
    THe yanmar had worst feul but topped 38knts
    The D-4 is really good with cruise of 18-22 with 4.5-5.4 gal per hr. planed with 6 drums of diesel and 100 gals below deck and 200# of groceries with 2 of us onboard for a 70 nautical mile run.

    Pick a motor you can have serviced locally or better yet ask your mechanic what he is willing to service.
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  12. #12

    Default Not apples....

    but my buddy runs a 34' Fiberglass catamaran Na Pali tour/fishing boat and burns 15 gals TOTAL for a 4 hour trip (this loaded with 14 passengers and running 15 knots or so into the trades). Boat is powered by 4 cyl. Isuzu (sp?) diesels coupled to Mercruiser Alpha 1's via jackshaft.

    The low-end Alpha drives have taken their share of opinions, but can't argue with the results. He is a maintenance nut (his livelihood depends on it) and is constantly checking leg oil, excessive play in parts, u-joints, t&t, and has 2 complete spare engine/drive packages. I believe these motors are 120 hp models; I know they're not in the range for the above poster's consideration, but just wanted to shed some light on the subject.

    BTW, the same guy used to run twin Volvo AD-41 DP's and sold 2 of the boats with about 10k hours on them (same engines, never rebuilt, torn apart, etc.).

    Key words here: Maintenance, maintenance, maintenance

    Jim

  13. #13

    Default

    Quote Originally Posted by potbuilder View Post
    Now i really want another lobstah' boat, big power, big rudder, big shaft, big transmission and no troubles.
    Amen to shafts and rudders. The only way to go, in my opinion.

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