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Thread: Re-power Cruisemaster 700 with diesel

  1. #1

    Re-power Cruisemaster 700 with diesel

    I have a Whittney cruisemaster 700 which has a 5.7l mercruiser 300hp carb engine with a bravo 1 drive. I am going to re power later this year and have decided that I will go diesel.

    I was looking at staying with petrol and replacing with a mercruiser 350 MPI seacore with a bravo 3 drive. I got quotes and researched different options until my head was about to fall off. I contacted Captain Rednut to have a look at my set up sometime back and have been conversing with Jim for sometime (sorry if I have been a pain Jim) and he has given me a great deal of ideas and advice on what he thinks should be the re- power. The cost from petrol to diesel re-power is quite a few drinks and had many conversations with the wife on the subject to get approval to spend the extra dollars that I will never recover in the short or long term.


    I made my mind up to go with the diesel as follows.

    • I carry 320 litres of fuel which doesn't give me a great range with the petrol inboard. I plan on spending 2-3 nights out when weather permits and the diesel will let me achieve this.
    • The engine I am looking at is a Yanmar 315hp with either a Bravo 3 or a ZT370. I am leaving that up to rednuts to work out. This is going to give me a better cruise speed than the petrol which this hull will be happier with. There are the bare electrics on the engine so I wont have electronic problems that can sometime drive you insane as I have had before.
    • The obvious one that its a little harder to get diesel to explode but the fuel injected petrol inboards are certainly much safer then years ago. The wife also said she would feel safer which sold her on the idea.
    • I am going to keep this boat and don't see me selling for many years after all the time and money spent. Happy with the boat has everything we need for cruising and fishing and can still tow without to much trouble to 1770 as this is where I wish to spend as much time as possible.



    I am not even getting into the money differences and cost of fuel or fuel usage as I have been down that road and enjoying my time on the water which covers in my book any money issues or hang ups. Boating is not a investment for your money as we all know. Hard to beat the rod getting pulled out of your hand and watching the sun set over the water.

    I am sure there are a few on here that have done what I am about to do and would like to know how it all turned out or may be changed your mind and stayed with the petrol. Anyone who has done this with a similar boat I would be interested on the performance difference. I will be adding an extra 100 kg in the boat and will need to increase the engine bay 100mm and possibly move the fuel tank forward which I am still to look at.

    I am doing lots of other work on the boat like removing the anti foul and upgrading radios etc. Have a long list of tasks to complete and will completely gut and detail the boat. Just in the process of building a trailer to have under it and the cost at the end will be something I will forget when I pull a nice red fish over the side.

  2. #2

    Re: Re-power Cruisemaster 700 with diesel

    From an outsiders POV, I reckon it makes a lot of sense. To make yourself feel a bit better, don't under estimate the future value of your rig with a diesel vs petrol. Ok, so you might not recover all the extra bucks, but it will certainly make it more attractive as a second hand outfit.
    Good luck with it all, look forward to seeing all the before and after performance figure
    fruit salad is the new Bacon

  3. #3

    Re: Re-power Cruisemaster 700 with diesel

    yep, I'd go with fishards comment there,,,
    you've obviously looked at the other boat option and decided to modify and re-power yours to suit your own needs !
    if the numbers stack up, go for it !
    your right, sometimes its not about the money, its about being happy with what your going to end up with !
    sounds like an interesting project ahead of you, good luck

    bonneville

  4. #4

    Re: Re-power Cruisemaster 700 with diesel

    Boating is never about the money. If it was, I'd be the first one to get a seafood business. You're 3rd point in it's own right would be enough for me. The fact you saved a few bucks by sticking with petrol would be of little consequence if the thing went bang.

  5. #5

    Re: Re-power Cruisemaster 700 with diesel

    What is the suggested hp required to replace the V8 petrol? I spied a 24 foot Savage with a flybridge for sale. It is powered with a 300hp Volvo, it has got me thinking about doing the same thing. Be interested in any updates as you go along.

  6. #6

    Re: Re-power Cruisemaster 700 with diesel

    Don't discount looking at the mercruiser TDI diesels

    have a pair of the 335 hp TDI V8s and they are sensational, and cheaper than the yanmar,

  7. #7

    Re: Re-power Cruisemaster 700 with diesel

    Quote Originally Posted by scottar View Post
    Boating is never about the money. If it was, I'd be the first one to get a seafood business. You're 3rd point in it's own right would be enough for me. The fact you saved a few bucks by sticking with petrol would be of little consequence if the thing went bang.
    Yes it was a major part of deciding if the extra cost is worth it. You don't get any chance with petrol if all goes wrong. The wife was happy for me to spend an extra 15k just for that extra safety. I take the son out most of the time and she likes to cook when we are out and having a bbq running was not her cup of tea. I think I was struggling more with the extra cost than her. She actually got to the point of saying she would not go out if I installed another petrol. The wife is not a good deck hand but a hell of a good cook. Keeping her happy is worth 15k I can tell you.

  8. #8

    Re: Re-power Cruisemaster 700 with diesel

    Quote Originally Posted by Bremic View Post
    What is the suggested hp required to replace the V8 petrol? I spied a 24 foot Savage with a flybridge for sale. It is powered with a 300hp Volvo, it has got me thinking about doing the same thing. Be interested in any updates as you go along.
    I spoke to many people over what HP to replace with and some said 260 HP diesel would give me what I need. Now they could be correct in this statement but speaking with someone who has re-powered many boats and ones simular to mine and listening to what I want in performance he was adamant that I go with the Yanmar 315 hp. I looked at all the different engines available and got in to many discussions about the pros and cons of the different makes. There are engines on the market that actually weight less than what I have now which one would think would be a good thing until you start speaking to the people that install and repair marine engines for a living. None I spoke too and they are diesel marine mechanics had anything good to say about these light weight engines and explained the reason why. Even some have said that you will not be able to re build these engines.

    I don't think I can go to wrong with the Yanmar. There are some good engines out there and some have very advanced technical systems which is great until they play up. They have good fuel burn as they are controlled by computer injection with a host of sensors. The yanmar is old school when it comes to this. I understand that Yanmar soon will also start bringing the same diesel injection out if they haven't already to comply with emissions standards I have been told. For my needs I was after something simple and proven which the Yanmar is. Many diesels now compliant with all the plug and play equipment and nmea 2000 for interfacing with all your toys and even your coffee machine. I am wondering how the hell you fix out at sea when a gremlin appears in the electrics.

    I will certainly keep up to date with progress but it will be later in the year before I complete the re-power.

  9. #9

    Re: Re-power Cruisemaster 700 with diesel

    I guess doing this conversion, weight of a biggish diesel is going to be a factor, a decent diesel is going to weigh a lot more than a similar petrol motor, especially when you are talking "heavy duty" as distinct from the light weight motors around today, lots of them have VW technology, and I wouldn't be too scared of what some diesel mechanics tell you about longevity and rebuilds, by the time any of them need a rebuild, with rec use, most people would be in a walking frame in a nursing home....

  10. #10

    Re: Re-power Cruisemaster 700 with diesel

    Quote Originally Posted by Noelm View Post
    I guess doing this conversion, weight of a biggish diesel is going to be a factor, a decent diesel is going to weigh a lot more than a similar petrol motor, especially when you are talking "heavy duty" as distinct from the light weight motors around today, lots of them have VW technology, and I wouldn't be too scared of what some diesel mechanics tell you about longevity and rebuilds, by the time any of them need a rebuild, with rec use, most people would be in a walking frame in a nursing home....
    I am not to far off the walking frame Noelm some days.

    The yanmar is only 100 kg heavier than what I already have and I would be carrying more than that in extra fuel when I wish to stay out a few nights with the petrol engine. The only real weight adding I would like would be some fish. The boat would come in at about 2.5 ton without bodies in the water and 100 kg is not going to hurt. The last person that owned it had 100m of bloody chain for the rode which would have certainly kept the bow down. I am also looking at moving the fuel tank forward which will be better to distribute the weight better as these boats do tend to be heavy in the ass a little. Even if I was replacing with another petrol I would seriously have looked at moving forward.

    You would class the yanmar as a light weight diesel also compared to some of the others. I think even the Volvo's are heavier for the same HP. Agree for rec use you would be lucky or unlucky to have to re build unless of course something goes wrong.

  11. #11

    Re: Re-power Cruisemaster 700 with diesel

    Hi Brett
    Ive got two yanmar installs on now that i can give you accurate speed and fuel data statistics on when complete and one boat is nearly a sister ship in size and weight but a different brand to yours with the same choice of engine 315 Hp Yanmar with a bravo Three drive and the other one is the same size and weight with a 260 hp BY ZT370 Drive so ill compare speed and fuel figures for you for curiosity.
    Cheers JIM

  12. #12

    Re: Re-power Cruisemaster 700 with diesel

    Hello brett62,
    have a look at these results.
    Same boat petrol V diesel on a similar weight boat to yours.
    http://www.########.com/boats/boat_video.aspx?ID=1893
    http://www.########.com/boats/boat_video.aspx?ID=1894
    Have a look at this website, they have actually installed and tested a very similar setup.
    http://www.australianboatmags.com.au/pub/index.php
    I am glad that you have got over the $$$$ because from a financial position it make no sense at all for a recreational user. You will never recoup the startup costs and maintenance on a high-tech diesel will be heartbreaking.
    If you don't believe me on that talk to a mechanic who services modern diesel cars.
    I see that you are at Caboolture so finding a competent mechanic should be easy enough.
    Diesel is safer from a fire, but if it ever does catch alight, stand well back.
    I assume that you have an LP gas bottle on board, I would be more worried about that.
    From the range figures above there would be no need to increase the capacity of the fuel tank.
    To test for the extra 100kgs, have some crew members sit on the engine box for a while.
    Make sure that the Yanmar is not made in China because I drive a work vehicle that has a Chinese diesel and it is hugely temperamental and no-one knows how to fix it.

  13. #13

    Re: Re-power Cruisemaster 700 with diesel

    Hello All,

    The #### are ########.

  14. #14

    Re: Re-power Cruisemaster 700 with diesel

    Try again,

    join the words boat and test, no space.

  15. #15

    Re: Re-power Cruisemaster 700 with diesel

    Quote Originally Posted by captain rednut View Post
    Hi Brett
    Ive got two yanmar installs on now that i can give you accurate speed and fuel data statistics on when complete and one boat is nearly a sister ship in size and weight but a different brand to yours with the same choice of engine 315 Hp Yanmar with a bravo Three drive and the other one is the same size and weight with a 260 hp BY ZT370 Drive so ill compare speed and fuel figures for you for curiosity.
    Cheers JIM
    Jim that would be great to have some data which will give me some idea of what I can look forward too. I am hoping to get my boat back on the new trailer soon so you can pull the motor out so you can work out what changes will need to be made to the engine bay. I am going to get the anti foul off first so I don't have too put the boat back on the stands. Jim are the two boats your setting up re-powers or new install ?

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