stainless or aluminum prop for '04 Merc. 15HP

Discussion in 'Prop Shop' started by ducktrooper, Jul 4, 2011.

  1. ducktrooper

    ducktrooper Well-Known Member

    Just got back from White River in AR and the universal consent among the rental boat docks is to use aluminum props on the rivers. Their reasoning is the aluminums might bend/break easier but they are cheaper to replace and repair.

    More importantly they claim the aluminum prop won't transfer as much of the impact to the lower unit on the Merc motors, which is almost always a $300 repair. The prop with my motor is OK but fairly frayed around the edges. I'm thinking of keeping as a back up and getting a new one.

    Do others agree here agree that aluminum makes more sense if you're constantly navigating rocky rivers with gravel bottoms and varying water levels? If so, what brands are reasonable and can you get them cupped?
  2. WhiteDog70810

    WhiteDog70810 Mostly Harmless

    I like stainless props because they hold up so well, but hitting solid rocks is rarely, if ever, part of my average day. I've heard the same thing about aluminum props breaking before the lower unit was damaged. I thought there was a shear pin to protect the lower unit from a prop strike. Am I wrong? Shear pin or not, if I was expecting to shred props on a regular basis, I'd buy two cheap props with the correct diameter and pitch. I don't see any sense feeding expensive props to the rocks. I wouldn't pay for cupping because it adds expense to something that will get beat to hell.


  3. noeettica

    noeettica Well-Known Member

    for gheenoe 10 pitch Solas aluminum 3 blade

    if really loaded down 9 pitch
  4. topnative2

    topnative2 Well-Known Member

    alum. all the time for small boats the increase in performance w/ small motors is negligible if any

    the problem w/ steel is that when going forward and strike an object it can bend the prop shaft up w/o showing any damage to the blades and continued use then kills the lower unit$$$$$$$$$$$$$$$$$
  5. The_Skiff_Shop

    The_Skiff_Shop Well-Known Member

    IMHO, on a 9.9 / 15 Merc 2 stroke, the best bang for the buck is the stock / OEM prop if you hanging a motor off the transom without mods.

    If a SS shows "negligible' difference, you most likely have not made the best choice for it's replacement.  That said - you can put the best racing tires known on your daily commuter, but I suspect you will see a "negligible difference" in the performance until mods are made to the vehicle. Once we start adding jack plates ect, is where you will realize the potential of the SS prop.

    This motor does not use a shear pin but rather a pressed in hub that is insulated with rubber to absorb shock for both AL / SS and designed to shear under heavy impact.  Mercury has a new design for this hub that is already used in larger motors that will actually let you "rehub" on the water.  It would be nice to see this design makes it's way down to the smaller motors

    The age old question of what does less damage, SS or Aluminum?  An unofficial survey deemed more prop shafts were bent with AL props.  But it was also noted that not only were there more AL props out there on these small motors, but also the owners with SS were generally more experienced and either idled with caution, or the motors were jacked up high enough that they cleared the obstacle.  Prop shafts bent per hit appeared to about equal.

    But as always, just my .000000001365 sense
  6. DuckNut

    DuckNut Brandon, FL

    In MI when we use boats to chase steelhead and salmon my buddies run a composite prop that has interchangable blades. They carry the tools necessary to change them on the river - only tool needed is a wrench- and these blades are like $13 so they carry several as the water is only 2' at most with nothing but rocks on the bottom.

    Prop smashing/breakage is common because the river is flowing quite fast and being under total control at all times is not possible. Jet johns are catching on up there because of the conditions.
  7. ducktrooper

    ducktrooper Well-Known Member

    I found a local prop shop that will recondition my OEM plate that has ruff edges for about $40....and he'd do a mild cupping at no extra charge. I think this is what I'm going to do for now until I nail down what other mods I plan to do and once I get more tach info with my new Sendec.

    I am observing some mild/temporary slippage at WOT and during turns, but it's pretty mild. With my jackplate all the way up on my Bob's JP, perhaps this cupping will be just the answer.