New to the boat scene and have a repower question.

Discussion in 'Diesel Engines' started by LBZ, Oct 3, 2009.

  1. LBZ
    Joined: Oct 2009
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    LBZ Junior Member

    Hi all. First off this is a great forum. I have been a lurker for awhile but finally I decided to join. I don't know a whole lot about boats so I am not sure how much I can contribute but as things go along, hopefully I become useful here!:)

    I just bought a '93 Bayliner Classic 2885. It has a 454 BBC Mercruiser in it that I would like to replace with a diesel. The boat weighs 8 to 10 000lbs when it is loaded with guys gear and fuel and as you can imagine, is VERY hard on fuel!!

    I have alot of questions so bear with me folks:

    What hp/tq of a diesel should I be looking for to move this beast at say 20 to 30 mph?

    What are some of the more popular brands and models of diesels guys are using to do repowers in these kinds of boats?

    Can the transom drive be re-used/adapted to the diesel or do I need to change it?

    I ASSume I will need to change the prop and possibly gearing but that is something I can look into after I decide which engine I go with correct?

    Thanks folks!:D
     
  2. WestVanHan
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    WestVanHan Not a Senior Member

    I suggest you talk to the proper marine specialists and get an idea for the costs and whether its is even possible.


    Take this cost and assume you will get 10-20% better fuel economy-take how much $$$ a year you spend on gas a year (with hours) and figure out how many years or even decades it will take to break even.

    Or you could just slow down.

    The costs could easily be what you paid for your boat or more...
     
  3. gonzo
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    gonzo Senior Member

    Yanmar makes a direct replacement and so does Cummins. However, unless you are a commercial operator, it will take many years to make up in fuel savings the $25K or so you will invest in a new engine installed.
     
  4. LBZ
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    LBZ Junior Member

    Slowing down isn't an option!:D

    The cost of the engine will be offset by the sale of the gasser. It has just over 1000 hrs on it and was recently refreshed. The cost of upgrading to aluminum heads and upgrading the intake would be as high $25000 anyhow, which is my only other option. Also, the diesel would increase the value of the boat and the fuel savings would also be a benefit so all said and done, I am estimating about 10 to 15000 dollars would be the cost of the swap providing I can use the existing transom drive.

    All the labor will be done by myself so there are more savings there. I just need to know which engines I should be looking into using.

    Which model of Yanmar and Cummins are most often used in these size of boats? What hp range?

    As far as fuel savings go, I spent $1400 CAD on a 250km 4 day trip and I make the same journey about 4 to 6 times a year so I would like to cut that as much as possible.

    Thanks for the input guys-much appreciated!
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Lots of boat-owners would like to swap their old gas guzzler for a diesel.

    If you have the knowledge, experience, time, tools and skill to convert a car or light truck engine, you might achieve your goals at acceptable cost. A friend or relative with all these qualifications who is willing to work pro bono or for a symbolic sum would be even better.

    Your post tells me that your situation is different. That you have to pay real money for a marine diesel and for the mechanic who should install it in your 16 years old Bayliner. WestVanHan's suggestion to calculate the number of years to the beak even point is sound advice. And you should bear in mind that the boat may not live long enough to reach that point.

    In the past I owned a very thirsty Glastron. To cut the fuel bill I switched to liquid propane/butane. The investment is minimal: a pressure reducer, electric valves and some plumbing. Because there are no LPG fuel stations at the waterside you need several bottles and must be prepared to do some hard labour swapping bottles before or after every trip. In most European countries LPG costs about 1/3 compared to gasoline, but in Canada that may not be the case.
     
  6. LBZ
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    LBZ Junior Member

    I've been a heavy equipment mechanic for 15 years and am an avid Diesel Drag racer so if it's one thing I know-it's diesels and how to fix them! I have lots of access to machine shops and the like to do any special mods I need to but like all machine shops-they aren't cheap so the engine swap with the least amount of custom required parts would be my best soloution!!

    Propane is not a viable option but thanks for the suggestion!

    What I don't know is anything about installing diesels into boats that currently are gas powered. I know very little about the goings on inside of the transom drive system, but I am learning. I do have a couple 4BT Cummins engines of various years that I can pick up for cheap but they may not fit my application or my hp requirements. They also would need the manifold changed over to run in a boat which I'm not sure anyone even makes. This is why I am asking the experts and more experienced boat folk on this forum for assistance in picking a suitable engine for this project.

    A little background on the boat, I picked it up for ~$35 000 CAD and have put another $20 000 into it so far with the addition of an aluminum rear wall for the cabin, a LARGE swim grid added to the rear, and a 20hp Mercury for a kicker so I plan to keep this boat for many years and it is in IMMACULATE condition. It was only ever in fresh water before I purchased it and was never left in the water-always on a trailer.

    Thanks again folks!!
     
  7. gonzo
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    gonzo Senior Member

    Why would you put aluminum heads on?
     
  8. WestVanHan
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    WestVanHan Not a Senior Member

    LBZ:

    From memory BB are about 650 pounds,prolly you have 350 hp one.

    Some rough figures:
    Yanmar 6LP:
    -315 hp peak,270 cont.
    -950 pounds?
    -rebuilt used $15-18k
    -new $27k?

    Cummins Marine 6BTA:
    -315hp peak,260 cont..
    -WOT you'll be around 70 litres an hour
    -as you know 1100 pounds
    -new are $20k +
    -rebuilt used $15k +

    Cummins 6BTA electronic-330 peak and $$$ more.
    Converted truck engine-250 hp cont and $$$????

    So right off ~100 hp less and 350-400 pounds heavier.
    Yes Cummins can be boosted up cheap/easy but after 6 hours of heavy load WOT.....

    I suggest you phone up a marine transmission place and ask for a price on another out drive.
    Check your drive and its torque rating-its gonna blow with ~700 lb ft of Cummins going thru it.

    Then there's the exhaust,fittings,controls etc =$$$$

    Engine mounts: was the boat designed with a diesel option?
    If not-I'd say forget it.Just cant glass in a couple mounts.

    How can it be $25k for AL heads and intake?

    Stay with reliability vs. go-go. A melted piston in Skookumchuck,Nakwakto,Seymour Rapids,or many other places=likely death.
    Anywhere else=severe danger.

    Good luck,let us know.
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    OK, that is a different perspective.
    The major step from an automotive engine to a marine one is to use water as a cooling medium for everything that now uses air. There are lots of diesel engines that would fit your requirements, but for most of these there is no water jacketed manifold. The boat engines with 200+ hp you may find relatively cheap will all probably be too large, too heavy and do not have the proper rpm.
    Anything that has about the size and weight of your old Merc. will be turbine boosted and have an intercooler like a 6 cyl. Volvo Penta. Such an engine would neatly fit to your stern drive and the only thing to change there is the prop.
    But these engines I've never seen offered at bargain prices.
     
  10. Red Tide
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    Red Tide Junior Member

    What's the difference between the bravo and bravo diesel outdrives? Can a (gas) bravo be retrofitted to a bravo diesel to handle the increased torque?
     
  11. gonzo
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    gonzo Senior Member

    I believe diesels are usually mated to Bravo II or III
     
  12. TollyWally
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    TollyWally Senior Member

    I've got a big block chevy in a 28 ft. boat and have looked at the cummins 6bt motors with lust in my eye. It's a decent swap both weight and torquewise. The motor weighs a bit more but it doesn't need to carry as much fuel. The cummins has gobs of torque.

    If you're a diesel mechanic who drag races them too, you are definitely the kind of guy who can pull this off and make it all worthwhile. Here are 2 websites for a little inspiration. One of them has some power curves on it.

    http://www.hsmarine.com/
    http://sbmar.com/

    If I had your skillset and connections there would be a cummins in my boat now and I would be tooling around with at least half the fuel burn I now suffer from.

    I think the diesel torque can be hard on outdrives. The rest of the marine conversion stuff isn't that hard once you have the exhaust sorted out. A commercial shopping newspaper, Boats and Harbors, is a good place to track down misc. diesel manifolds, parts, and takeouts. Go for it, the folks here will help you out on some of the marine minutia if you get puzzled or stuck. You'll have a bit of a time tuning the prop to the new torque curve but that's a good problem! :)
     
  13. LBZ
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    LBZ Junior Member

    I have a Bravo II in my boat but for $5000 on a trade I can upgrade to a Bravo III.
    As far as motor mounts go, I would have to look at the Yanmar and the Cummins and see how they mount. I believe I should be able to adapt to BBC mounts-even if I have to make a subframe out of chromoly tubing or similar.

    Exhaust shouldn't be a big deal, just changing from a Y-pipe to a single pipe off of the exhaust with some custom tubing should do the trick in my eyes. I should be able to use the existing standpipe as it is 3.5" already.

    The fuel tank is aluminum so that is a plus as I should just have to change the fuel sending unit.

    Gonzo, the aluminum heads would be an upgrade including fuel injection for a little more power, less weight, better heat transfer and hopefully a little better fuel consumption. But at that sort of cost-it's not worth it too me.

    Thanks for the input guys! I have a bit of a better idea now on what this is going to take. IF I start to make it happen, I will be sure to keep you guys along for the ride!!
     
  14. WestVanHan
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    WestVanHan Not a Senior Member

    Hey LBZ:

    Just thinking, there are Bayliner forums out there...theyd be the guys to ask if a 6 cylinder can be mounted.

    Knew a guy years ago with same boat,the diesel version of that boat was the 4 cylinder 240 horse.Dunno if they made 6 banger.

    Let us know or paste a link to your thread.

    Good luck
     

  15. LBZ
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    LBZ Junior Member

    The 4 cyl would probably be enough. With the torque it creates, I think it would be fine. This is why I was thinking a 4BT cummins mechanical engine, but I'm just not sure about the manifolds.....
     
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