Tweaking/Modifying a 50 HP Merc

Discussion in 'Outboard Maintenance' started by devinmurray99, May 4, 2010.

  1. devinmurray99

    devinmurray99 Well-Known Member

    Without tearing apart the powerhead on my Merc is there anything I can do to tweak and modify the motor for better acceleration?  For example can I upgrade the carbs, wires, plugs, etc?   I don't want to fool with the prop sizes because she accelerates pretty good with at 13 and revs a little high with an 11.  I am researching before buying a pair of 9 x 9 Lencos.  Any ideas?
  2. Brett

    Brett > PRO STAFF <

    Good topic to go with my morning coffee.
    Let's keep it simple, no need for technical details.
    First, a question or two to think about:
    Is increasing the performance of your motor going
    to increase your speed or hole shot substantially
    enough to justify the amount of money needed to
    accomplish the task? Or, would it be easier and faster
    to sell your existing motor and buy a bigger one?
    We're talking about fishing here, not racing for cash prizes.
    Sure, you can get another second faster out of the hole,
    or add another few miles per hour by tweaking the
    engine you have, but it's actually easier
    and cheaper to just hang a yami 70 on the back.
    Increasing the performance of an outboard,
    actually shortens it's usable lifespan. They are built
    to last only so many revolutions of the crankshaft.
    The faster you use up those rev's, the sooner you'll
    need to spend more money buying another outboard.

    Back to speed...very simple...want to go fast?
    Lighten and balance the load, minimize wetted surface,
    increase horsepower, buy a better prop, power jack plate
    and a quality set of powered trim tabs.

    Ahhhh, heckuva good cup of coffee.... ;)

    Still feel the need for speed?
    Talk to these guys about spending money...

  3. firecat1981

    firecat1981 BBA Counselor

    Hey Brett, if he did somehow add Hp to the motor wouldn't he change his RMP range and need to buy a new prop anyway?
    I say just buy the trim tabs, it will be cheaper in the long run, or buy a SE200 or dolfin they work well too.
  4. Brett

    Brett > PRO STAFF <

    FC, I learned like you did, one small change to a boat
    can cause all sorts of unforeseen consequences.
    Easiest way I found to decrease my hole shot time,
    was to balance the load in the hull. Too much weight aft
    causes the boat to squat. Moving weight forward
    allows the engine to push the hull over the bow wave easier.
  5. devinmurray99

    devinmurray99 Well-Known Member

    I should have been more specific in explaining my purpose but when I am loaded down with fuel, full baitwell, etc. and two passengers one typically has to move in front of the console to get on a plane.  After reading your post and thinking about it, it isn't necessarily a hp issue, it seems like a weight distribution issue.  I say this because when two people sit in front of the console it planes-out seconds faster.

    For months now I have been thinking just to leave the motor and prop alone but opt for a set of trim tabs and a jack plate ($425 and $190 respectively) but I was unsure if there was something else I could do.  I have a Doel-fin from the old 40hp and haven't really considered drilling holes in the new motor to test it out.  I still not sure how I feel about that.   

    Until then I guess I need to read-up on lightening the load and learning how to redistribute it.  Thanks for the input guys.
  6. aflatsnut

    aflatsnut I Love!

    I'm not familiar with your hull but the problem could be not enough negative trim in the motor. In other words, the motor might not tuck under enough and would be as if you were trying to start out with the motor trimmed up. If this is the case you could install a set of wedges between the motor and the transom. I believe the wedges come in a couple of sizes, 5 and 10 degrees. This will allow the motor to trim down more, or tuck under, and get you on plane sooner.

    Another thing to check first would be the tilt pin. On my 50 Yam I just removed it. This would prevent the motor from tilting down completely and give the same symptom. The tilt pin is what sets the trim angle on non electric outboards.

    Hope this helps.

  7. firecat1981

    firecat1981 BBA Counselor

    what kind of baot is it, can you post a picture? also if you go with the SE200 and the sportclip then you don't need to drill your new motor.