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Boyesean reeds & porting

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  • Boyesean reeds & porting

    Hi again,
    looking for some opinions. I’m doing a complete rebuild on a 2001 150 Mercury Carb. My marine mechanic recommended that I port the engine and install boyesean reeds to increase performance. Is this worth it? He said I’d gain 25 hp but I don’t know how accurate that is or the benefits of increasing the hp by 25. I have a proline 20’ walk around. I’d love to hear the pros and cons, thanks.

  • #2
    I have no idea. 25 HP gain is 17%, pretty healthy gain considering all you are doing is helping air flow in an Air Pump essentially. Back in the 1950's porting and relieving V8 flat head Fords was the thing the hot rodders did. Course Ford had a problem with exhaust air flow in that engine anyway as it had to go through the block to get out, unlike OHV engines where you could have Hemi heads and smooth cross flow. Two stroke outboards are already setup for smooth across the piston air flow.

    On the reed valves, never heard of any results but read on here where they were used by hot rodders. Merc already has a pretty fancy "Rose Pedal" reed valve on their mid range engines...don't know about the big V6s.

    Ping Faztbullet or Racerone for a couple of suggestions for where to find help.

    Edit: Ford used sand castings for their blocks which made the interior rough causing somewhat "turbulent" air flow whereas modern Merc engines are "Lost Foam" cast providing for much smoother surfaces without any machining in non critical areas.
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.


    • #3
      Your engine is likely the 2 liter, Porting if done by someone who knows what they are doing can add Horsepower, but anytime the Torque Curve is shifted to a Higher RPM range, the Low End torque of the Engine will suffer.
      When Merc was developing the V6 in the early 70s, they attained over 200 horsepower out of the 2 liter, They changed the effective Port Timing, not by changing the ports, but by Beveling the edge of the Piston(cheaper and quicker to test changes). Though the engine did make the power at the top end, it didn't have the desired Powerband for Recreational Usage, so when Merc brought out a 200, it had more Displacement

      Boyesen Reeds, to me are a gimmick, something to Namedrop at the Dock/Launch. They are made from a very thin Fiberglass sheet. While they do offer slighter better response to air pressure changes than the stock Steel Reeds, they have a very much shorter Lifetime, and need regular inspections. Their only real Potential advantage is when they do break, and they will, they don't do as much Internal Damage to the Engine as a Steel Reed would. However I have only ever seen one OEM reed break, and that was after the owner allowed the local 'expert' to modify(bend) the reeds on the promise of more speed/power.


      • #4
        Thanks for the input guys. It seems like maybe the $500 could be better spent elsewhere. I definitely don’t want to lose low end power from this modification


        • #5
          it is a 2.0 motor.. o-ring block and heads.. not a candidate for compression change which would add more performance than most anything else... reeds add nothing but a little better idle and throttle response.. lots better brands on tha market, ie: chris carson, tdr ect… porting a 2.0 ta get more hp requires someone that knows exactly what they are doin' and expensive.. it can be done right without losing low end grunt but this is usually done for lite weights.. waste of time and money in your case... your boat needs a 2.5 200 on it... or at least a 2.5 anything...
          Last edited by Dukedog; January 8th, 2020, 05:38 PM.


          • #6
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            Many years ago had a new 125 dirt bike ported and polished. Of course we always ran boysen reeds. A little practice and proper carb jetting that 125 was very fast in the upper rpm range. No stock 250 was even close. The boy won championship that year with two races left. We did rering after every other 2 hour race. A pipe was also in the mix.

            if porting is done right power can be added. Rejetting may also be needed as more gas will be passed thru for full throtel power. The entire exhaust will need to be done also.