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Thread: 4 blade stainless ?

  1. #1
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    Default 4 blade stainless ?

    I have a 1852 Alweld with a Yamaha 70 2 stroke, and I was thinking of replacing my 3 blade aluminum with a 4 blade stainless impellor. I hear different stories both good and bad and was wondering if anyone had a similiar set up.


    thanks

  2. #2
    Member atvalaska's Avatar
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    Thumbs up go with the 4b ss

    lasts longer in our silt water, my last two moters ran better(smooth'r) /on step faster w/them and it's got some wt...... and acted like a little fly wheel....98cents worth of info..
    WHEN IN DOUBT> THROTTLE OUT.......

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    Default

    I have a 4 blade stainless on my 22 foot hewescraft with 150 yamaha. The 4 blades get me out of the hole quicker; however, give up some on the top end speed. Great for the saltwater, putting people on the beach is easier no aluminum props to refile when I get into the small rocks near shore.

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    Default IMHO the 3 blade is better

    I have a 150 Yahama saltwater series (2 stroke) on a Alumaweld deep vee
    19 ft. Thinking that the 4 blade I have for a spare would be better - I changed it out for a couple trips this summer. With the 3 blade stainless I can run at 3800 RPM and get 28-29 MPH. With the 4 blade at the same RPM I get 23-24 MPH. I have found that for me the 3 blade runs smoother and is far more economical on fuel.
    Maybe have one of the dealers lend you a test prop for a weekend and see what results you get. Any dealer that sells new boats usually has a few sets around for testing on new boats.
    How stupid is it to be wasting tons of salmon and halibut as bycatch in the Bering Sea and then have the coastal villages hollaring they have no food? It's got to stop!

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    Default Akfishnut

    Are you talking props or impellers? I gotta believe at those RPM and speeds you are talking about props. If so, pretty hard to compare props and impellers.
    Wiso, I have an OMC 88. Once I wore out the aluminum 3-blade I went to the stainless 4b. I never looked back. But then I never had a 3b stainless to compare to either.
    I can't say as I have ever been unhappy with my set up.

  6. #6

  7. #7

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    I'm sure you're well aware that correct prop selection in diam/pitch is critical to this discussion. I fish often on a fiberglass boat that weights about 4-5 thousand lbs. and is powered by twin high thrust Yamaha fourstroke 60's. My buddy went thru quite a few props to finally compromise on 4 blade ss. (I've seen it said that boats are all compromise?)
    Results: the 4 blades give better hole shot performance/torque at lower speeds and are smoother/less cavitation/vibration but sacfrice top end speed and some economy (minimal at trolling speeds).
    Kinda depends on use & conditions (here it's usually blowing 10-20 knots on the ocean so top end speed is a non-issue). We spend most of the time trolling at approx. 7 knots and when running somewhere it's sufficient just to get the boat to planing speed.
    The boat burns 2-2.5 gph trolling speed.
    Good luck, Jim

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    Default

    In my own experience the only time a 4-blade impeller was beneficial was on a high-powered motor that could cavitate the impeller at take-off. The power was great enough to spin an aluminum 3-blade impeller without getting a bite (200hp Merc). I've never had that problem on my own 50-60 hp motors. I do have a 6 1/8" 4-blade stainless impeller that I've tried on a 50 2-stroke and 60 4-stroke (powerhead) jets. The initial spool-up was no better and the top end suffered so it only serves as a back-up unit. On this forum I've learned the Glen Wooldridge now makes a 4-blade SS impeller with a milder pitch and Outboard Jet is making SS 3-blade impellers. I'd be interested in those if I had a durability problem with aluminum but I don't.

  9. #9

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    This is the first time I've heard of a prop being referred to as an impeller. Is this something new? I've always know an impeller as being something that's inside a pump or jet. I don't care what anyone calls it, just curious.

  10. #10
    Member chico99645's Avatar
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    Default

    I played the Pitch and 3 vs 4 blade prop game most of the summer. Deweys was very helpful in letting me swap props once I talked to the right guy. I settled on the 4 blade. Don't remember off hand all the stats I recorded, but my main problem was not 3 or 4 blade, it was pitch selection. With seas and weather conditions continually changing, fine details on 3 vs 4 blade, the only real thing that I personally experienced was hole shot. As far as Aluminum vs SS. If price is not an issue SS is the way to go. I personally keep SS on and have spare Aluminum. Only takes a few minutes to change if your going in a river or areas that might have prop hazzards. Changing on the trailer only takes minutes. Changing at sea in a dingy is not fun, take my word on that one.

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    Default still debating

    The more research I seem to read about jet impellers the more confusing it seems to get. I would hate to buy a 4 blade SS ($550 at boat shop) and then have it not improve performance. I looked online and rerally havent found them much cheaper. Everywhere I looked all say for bigger engines. I havent found a 3 blade SS impeller.

  12. #12
    Moderator Paul H's Avatar
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    Default

    Unless a boat is way off with it's prop or impellor, or the existing unit is trashed, you aren't going to see dramatic improvements by changing the number of blades. It's a fine tuning thing and sometimes you'll see a 10% improvement in performance, other times you'll loose 10%, other times performance is unchanged.

    If you're really after more power, the only way to get that is to put a bigger engine on the transom.

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