Understanding O/B HP ?

Discussion in 'Powerboats' started by gerard baladi, May 12, 2005.

  1. gerard baladi
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    gerard baladi Junior Member

    I have been trying to choose between O/B engines Say Mercury Verado. The specs for the 200 Hp 225Hp 250Hp & 275Hp are identical .
    To be more precise, The models stated above have the same RPM range, same displacement, same Bore/Stroke, same gear ratio, same weight.

    How and where do they get the extra HP?

    Assuming also that they have the same propeller size and pitch would the extra Hp to get higher end speed or better performance through out?

    I have given the Verado as an example, but I have seen the same similar specs on 2 strokes engines by other manufacturers as well.
     
  2. Alan Power
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    Alan Power Junior Member

    Hp

    I don't know anything about the verado but my gues is that the lower HP's are just detuned versions of the same engine.

    With two stroke outboards there are differences in porting, tuners, carbs and intakes.
     
  3. marshmat
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    marshmat Senior Member

    To save on tooling costs, all outboard makers will use the same powerhead and chassis for several different engines. For instance, the Verados you mention; same for a Merc90 and Yamaha 100; same for a Johnson 25 and 30, etc, etc... (Note also that over 15hp they round the actual power to the nearest 5, over 75, to the nearest 10hp- ie. a 90hp could be from 85 to 96 or so)

    The lowest engine in the series is detuned a lot. It has smaller carbs or throttle bodies, fuel and airflow restrictors, sometimes lower rpm limits, but the same internal components. To get the higher powers, they might put bigger carbs, more potent injectors, maybe a better-tuned head.

    Outboards of the size you mention should not include propellers. Unlike a 20hp motor, which will push most boats it will see using the same-size prop, a 250hp engine requires a prop correctly sized for your boat/motor combination. A good dealer will have you test-drive your rig with a few different props to find one that is suitable.

    The higher HP will typically give you better acceleration and more top-end speed. For the same displacement, fuel use at a given speed will usually not change much between motors in the same series.

    However, if you want long-term reliability more than speed, always go with the smallest in a series. The higher models place more stress on the same parts and so will always wear out faster and break more readily.
     
  4. gerard baladi
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    gerard baladi Junior Member

    Thank you for the replies, I had the feeling that in the same series the lower HP would have less stress & live longer.
     
  5. hmattos
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    hmattos Senior Member

    If you look at the Evinrude website, you will see the same pattern of horsepower against capacity as other brands. However, being direct injection two strokes, the whole deal is controled be the computer EMM engine management module. Evinrude reprogramme the chip to allow higher revs, and to pump in more fuel - hence more horsepower. So, like European cars and vans, These days you can take your engine to a friendly dealer and he/she can plug in the laptop and reprogram the chip to give extra power. Why do you think they charge so much for replacement power head covers and logos? So that we do not all buy a lower power engine and haveit re programmed to save money.

    By the way, we build very fast RIBS here in England, which can compete with the US bass boats for speed with an outboard - 60 mph plus with a 200hp - see www.explorermarine.co.uk
    Regards
    Hugh Mattos
    Explorer Marine
     
  6. gerard baladi
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    gerard baladi Junior Member

    We would still have to find a friendly dealer that would agree to cut off on his profits by selling you a 200Hp and upgrade it to 250Hp. (!!!!)
     
  7. hmattos
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    hmattos Senior Member

    The dealer makes almost the same from the 200 as from the 250, and he would of course get the profit from the new hood and make a ( probably cash only) charge for the retune, so he will still be in profit. However, this is usually only done on older cars/trucks/ outboards where the new owner wants it to go faster and the warrabty is long since passed.

    I do not know about you, but on our boats - www.explorermarine.co.uk - we would probably fit twin 150/175 rather than the single 250. Makes the customer feel safer if he hits a log etc, he can still get home.

    Regards
    Hugh Mattos
    Explorer Marine
     
  8. gerard baladi
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    gerard baladi Junior Member

    Very true, specially here on the Red Sea, you could be easily stranded at sea untill you would get any help. Therefore twins are a must for safety reasons. And as I am planning for a 30footer a twin 200HP is what I am looking for at this time.

    As for the Evinrudes, any input as to their performance, maintenance etc.. I had heard rumors that their older models were not so good, any truth ?
     
  9. marshmat
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    marshmat Senior Member

    Given the choice I'd always go for twin. My current boat is too small (30hp Johnson) but if going offshore with outboards, twins are the way to go.

    Most older Evinrudes were pretty nice engines. Evinrude/Johnson are very closely related and I have seen some of both brands that have run for 20, 30, 40 years without trouble. The troubles you refer to are probably the FICHT ram-injection models. These engines had a mechanical high-pressure direct fuel injection system that was very prone to sudden breakage or gradual wear. Non-FICHT Evinrudes have a very good reputation. If you want 2-stroke direct-injection you might have better luck with Merc or Yamaha; if you can handle the weight, a 4-stroke is cheaper to operate and usually more reliable.
     
  10. mackid068
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    mackid068 Semi-Newbie Posts Often

    It's just like computers...dirty, evil corporations (not all, but many).
     
  11. gerard baladi
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    gerard baladi Junior Member

    My understanding is that 2 stroke Mercury's Optimax and Yamaha's HPDI run as cheaply as the 4 strokes, albeit the noise. 4 strokes don't come in cheap either.

    In today's progressing technology outboards come equipped with computer chips to contol the operation. Gone are the days when you had a problem at sea you could fix it with a common screw driver and pliers, Now you have to be towed to the nearest Dealer.
     
  12. mackid068
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    mackid068 Semi-Newbie Posts Often

    Yeah, the more advanced technology gets, the less intuitive and easy-to use it is (aside from Mac OSX w00t!)
     

  13. cyclops
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    cyclops Senior Member

    I have 2 old Evinrude O/B, 1988 & 1990. NEVER changed a part in either. Plugs and impellors O K. Computer should do much better. Right?
     
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