25 HP Outboards Choice

Discussion in 'Outboards' started by SukiSolo, May 20, 2014.

  1. SukiSolo
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    SukiSolo Senior Member

    Does anyone have any feedback on which would be the optimum 25 HP outboard for Sailing Club use?

    It is most likely a choice between the Tohatsu/Nissan EFI or brand new Suzuki EFI. I realise that these are pretty new motors so hard to get anyone who has used them. However the Suzy fuel efficiency figures suggest reasonable extra purchase cost over fuel saving. The motor will be doing a lot of idling, and low speed coaching work. The hull is a Dell Quay Dory (Boston Whaler type) and 25 HP is pretty much optimum for it's 13' length. 200+ hours per year, most likely 70% at idle and low speed where it is claimed the Suzy is significantly more fuel efficient. Different at top end where consumption curves align.

    We have had a lot of gearbox/selector problems with a Yamaha (40) so that is a bit off putting and the Honda has a very low alternator output, hardly ideal for a lot of idling.

    Ver much appreciate any comments.
     
  2. PAR
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    PAR Yacht Designer/Builder

    Maybe a high thrust model for the low speed stuff, where the better gearing will help. On the other hand, why not twin 10's, one to putter around on, the other for the occasional high speed blast.
     
  3. rustybarge
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    rustybarge Cheetah 25' Powercat.

    as far as I know the Suzi lean burn are only 20% More efficient in the 3500 to 4500 rev band. so it is doubtful if you would see any saving at idle speeds.

    ....still could make good sense purely on the available range increase at cruise speeds on a small dory.
     
  4. SukiSolo
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    SukiSolo Senior Member

    Thanks for the comments PAR and rusty. We recently replaced a 9.9 Mariner with the 2013 Suzuki 9.9 and that is a much better engine, with a very suitably rated prop giving good drive. Only niggle is it needs a longer bracket for the 'washing line' steering...it will be extended.

    The consumption figure chart I have seen (Suzuki internal testing) suggests much better figures at idle through to around 4,000 rpm. Looks around 9-10% better, maybe 15. As the motor will comfortably get the hull on the plane and then you can drop the throttle into this range, it should start to payback (fuel wise) in year 4. The current Mariners (25s') are 2001 (2 off one long, one short shaft) and a 2004 (short shaft). All have had the flywheel/starter ring replaced in the last three years as the magnets started disintegrating. Very lucky not to have done a lot more damage too. Fortunately when presented with a piece of magnetic sintered material I knew wher it must have come from!. Voltage regulators, a couple of them, and a lot of small niggly bits and pieces. All annually serviced properly. Hours wise anything from 3 to over 4k.
    Not quite robust enough to endear the Mariner/Tohatsu/Nissan engineering.

    Not sure we could mount 2 10 HP on the transom, it is really designed for one motor mount with aluminium reinforcement plate. Also rod/cable steer would have to be sorted out to work with that arrangement.

    The hull is good enough to see out another engine at least. Unlike RIB's these glass workhorses are pretty durable with a modicum of care.

    Thanks for the constructive comments.
     
  5. rustybarge
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    rustybarge Cheetah 25' Powercat.


    You are quite right, Suzuki are claiming better economy right through the speed range; different from last year when I was looking at their site where the leanburn blurb claimed saving only in the mid cruise range.

    ... Maybe the system has been remapped.
     
  6. SukiSolo
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    SukiSolo Senior Member

    The new Suzuki is a triple in line with offset crank (to cylinder centre) a very different beast to the prior V twin. It is so new that they have not yet arrived in the UK but may have in the US. Due in by end of month. Designation DF25 and DF30, these replace the older units. Spec is actually quite good.

    My guess is the bean counters got to the old V twin as it has a lot of carburettor breathing problems apparently. If it does not have two individual carbs and kept well synchronised it could be problematic. Nothing inherently wrong with using a V configuration for better primary balance and torque.

    I was hoping someone may have got their hands on one of these beasts (DF25) to get an impression of the unit. The Tohatsu/Mariner I have seen and heard.
     
  7. FAST FRED
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    FAST FRED Senior Member

    HONDA 4 cycle.
     
  8. SukiSolo
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    SukiSolo Senior Member

    The Honda is OK, but the alternator output at 10 Ah is a bit low for a unit that will spend 70% + at idle or trickle speed. Hence may not keep battery charge up especially in the winter.
     
  9. rustybarge
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    rustybarge Cheetah 25' Powercat.

    If you look at the latest free copy of 'Motorboat Owner' where they test the latest leanburn Suzuki 150hp, it burns exactly the same as the old Honda 150hp: 4.5 gals/hr at 4000 revs/20 kts.

    http://www.motorboatowner.co.uk

    Not very leanburn at all!!!:(
     
  10. FAST FRED
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    FAST FRED Senior Member

    output at 10 Ah is a bit low for a unit that will spend 70% + at idle or trickle speed.

    A fairly new battery will internally discharge about 1% of its capacity per day.

    That and a couple of starts a day will not tax the Alt.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    What about other RPM ranges ?
     
  12. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Here's a very accurate consumption test from PBO magazine in 2008:

    [​IMG]

    if you look at motorboat owner you can compare the data: sports boat type 6.2 mtr by 2.5 beam 1.3 ton displ.
    Suzuki 150 leanburn OB.

    1000 3.2 kts 2.2ltr
    1500 5.kts 4
    2000 6.kts 6
    2500 7.kts 10
    3000 9.5.kts 14
    3500 12.5.kts. 19
    4000. 20kts. 21
    4500 24kts. 28
    5000. 27kts. 35.5


    .....so: there's no saving at low revs, no saving at cruise of 4000 revs.......But considerable savings over 4500 revs.

    Surprising !!!
     
  13. Grey Ghost
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    Grey Ghost Senior Member

    Another endorsement for the honda fourstroke.
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    Thanks mate, I was under the impression the suzuki might have been a little better in the lower cruise range, but probably not much different. With a 25hp motor, not worth worrying about .
     

  15. SukiSolo
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    SukiSolo Senior Member

    Well, the Suzuki is now on order. I will let you know how much better it is on fuel than the 2004 Mariner on the other almost identical hull. Only 25Hp but that is all we need. Fun thing is now on the little Honda 2.5HPs' which you turn 180 degrees to reverse. We have been mandated by the RYA to wear kill cords above the knee and must be on leg. A couple of 2 stroke permanently in gear Mariners are similar. Just wondering when the kill cords wrap themselves around and around....

    Last year we were told the cords must be round the wrist.....
     
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