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How to get more power out of 115 HP Mercury on Trophy 1903 CC

DJWDJW Posts: 543 Officer
Hello,

I have a Trophy 1903 CC that is a bit underpowered with a 115hp Mercury.

How do I go about getting a new prop that will give me a bit more power? I assume that the one I currently have is stock but I purchased the boat used so there is a chance it is not.

I don't even know where to begin.

Thanks.

Replies

  • duckmanJRduckmanJR Posts: 21,171 AG
    What is your motors RPM "red line" listed as MAX RPM in manual ?....and what will your motor turn RPM wise with what you have on it now? Is it Aluminum..or Stainless steel? What is the size ( pitch X Diameter)You will need to know these before moving forward.
    There are many roads to travel
    Many things to do.
    Knots to be unraveled
    'fore the darkness falls on you
  • DJWDJW Posts: 543 Officer
    The redline is 6000. I typically run at 5000. Not sure how high it goes, over 6k but I don't usually run it that way.
    The prop I have now is stainless.
    How do I measure the X diameter?
    Thanks.
  • capt louiecapt louie citrus countyPosts: 10,396 Moderator
    Is 5k RPM at WOT ? if yes then there is some room. If you can get 6k wide open then it is what it is.
    "You'll get your weather"
  • DJWDJW Posts: 543 Officer
    No. Wide open is up over 6k somewhere but I cruise at 4.5 to 5k.
  • capt louiecapt louie citrus countyPosts: 10,396 Moderator
    DJW wrote: »
    No. Wide open is up over 6k somewhere but I cruise at 4.5 to 5k.

    Sounds like it's propped for the hole shot and by adding some pitch to reduce the rpm's down to the mid 5k area it would be tough to get up on top. If it jumps up really easy now then a bit of pitch increase will add top end and a bit of fuel economy.
    "You'll get your weather"
  • DJWDJW Posts: 543 Officer
    Ahhh, I think I see now.

    Right now it gets on plane easy but I would I would like more top end.

    Since I have some rpms to burn I can take a bigger bite of the water and get more thrust.

    The drawback could be less acceleration but the payoff will be higher top speed.

    So, I want to buy something that is the same number of blades, same diameter, but more aggressive angle of attack?

    How is angle measures when dealing with a prop?
  • duckmanJRduckmanJR Posts: 21,171 AG
    Look at the number printed on the hub of the prop...call your merc (assuming merc prop) and tell them that number and they can tell you both pitch and diameter.
    Many other prop brands have the P X D printed somewhere on the prop.
    There are many roads to travel
    Many things to do.
    Knots to be unraveled
    'fore the darkness falls on you
  • duckmanJRduckmanJR Posts: 21,171 AG
    DJW wrote: »
    How do I go about getting a new prop that will give me a bit more power?


    You asked here for " Power"...but it seems as though you want speed in your other posts.

    Here is the simple axiom (it is general).... DIAMETER = MOVES WEIGHT
    PITCH = PERFORMANCE

    For instance...a large non high performance boat would use a prop that is nearly "square" (same diameter and pitch)

    In high performance applications...Diameter is small with highly exaggerated pitch. In true racing application the prop is used to LIFT the hull clear of the water and is the pivot point along with the two rearmost corners of the hull...This is called " Aired out "...If you watch race boats you will be able to see this in action.
    There are many roads to travel
    Many things to do.
    Knots to be unraveled
    'fore the darkness falls on you
  • DJWDJW Posts: 543 Officer
    What should I pay?
    I said stainless, but looking closer it is black painted aluminum.
  • DJWDJW Posts: 543 Officer
    Sorry duckmanJR, I did say power but I mean overall speed. Forgive me, I am new to this...

    To say what I want another way, I get out of the water pretty good and I don't tow very often. I have a top speed of about 30 and I would like to bump that up.

    Thanks.
  • DarcyDarcy Posts: 1,711 Captain
    You need to go out. Put the throttle all the way down. Trim it up until the prop blows out a bit. Then just bump the trim back. Record your wot Rpms and your speed (gps).
    Then post those numbers. Running that motor at 6000 is no harm to the motor. I have mine propped on a light load to go 6200.
    "No i'm NOT Darcizzle!":blowkiss


    https://captainsforcleanwater.org
  • BarrellBarrell Posts: 1,263 Officer
    I always prop my motors to go right to redline. Why not use those last 1000rpms?
  • screamin seamanscreamin seaman Posts: 1,492 Officer
    Barrell wrote: »
    I always prop my motors to go right to redline. Why not use those last 1000rpms?

    Yes, with a light load. That way when you do add some weight to the boat it is still in the operating range and performs decent.
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  • lckirklckirk Posts: 87 Greenhorn
    I also have a 115 mercury EFI on a 19 ft bay boat and it has a Vengeance 15 pitch prop. My acceleration is terrible and I am trying to get better acceleration. What prop do you have on your boat.
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