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Thread: outboard jet impeller questions

  1. #1

    Default outboard jet impeller questions

    I am currently runing a Yamaha F50 outboard jet with the stock aluminum 3 blade impeller. Is there any advantage to going with a 4 blade stainless impeller? I would trade top end speed for hole shot and load carrying, I mainly run the Kenai so more HP is not really an option. I would like to upgrade to stainless and keep the aluminum for a spare.

  2. #2
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    Quote Originally Posted by beluga View Post
    I am currently runing a Yamaha F50 outboard jet with the stock aluminum 3 blade impeller. Is there any advantage to going with a 4 blade stainless impeller? I would trade top end speed for hole shot and load carrying, I mainly run the Kenai so more HP is not really an option. I would like to upgrade to stainless and keep the aluminum for a spare.
    The 4 blade will give you a little more torque for getting over your bow wake and running with a load better than a 3 blade. The 3 blade wil do the same job, just takes a bit longer. A alum 4 blade impellor will do the same as a S/S one, just won't last as long is all. Go with the s/s impellor and alum sleeve set up. DO NOT DO BOTH WITH S/S!!! Something has to give when ya get a rock in there and it's better for it to be a cheap alum sleeve than an S/S impellor, shaft, bearing or worse... Always keep a good sleeve AND impellor for backup. Not to mention shims, nut, cotter pin and a water pump. Good luck...

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    Member akshrop's Avatar
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    I swapped to ss on my last boat (60HP) and was very disappointed. Spent lots on money, lost speed, and never noticed an increase in torque. Another thread in here talks about ss impellors and many caution that the switch is only worth it in higher HP engines than you are running. I don't understand the physics, but it didn't help me at all. Good luck in whatever you decide.

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    Member alaskanmoosehunter's Avatar
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    The obvious reason for SS is durablity. If you plan on running shallows alot it might be worth the trade. Most lower HP motors there really isn't a notice in any performance.
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  5. #5

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    Quote Originally Posted by akshrop View Post
    I swapped to ss on my last boat (60HP) and was very disappointed. Spent lots on money, lost speed, and never noticed an increase in torque. Another thread in here talks about ss impellors and many caution that the switch is only worth it in higher HP engines than you are running. I don't understand the physics, but it didn't help me at all. Good luck in whatever you decide.

    The Outboard Jet Corporation recommends an aluminum sleeve and impellor on small outboard motors. They say the difference in performance gains will be negligable. SS props and impellors do not flex as much and they are more durable. No arguement there.

    But, with little motors, little propellors, or little impellors, there is not much flex anyway as the propellor and impellors are not huge and don't have an agressive bite anyway. By nature, they just don't flex much. I agree with akshrop, nearly everyone I have talked to about SS props and impellors running a small outboard motor have been disappointed.

    Now, if you are running a 450 hp inboard, now that is a different story. It can really make a difference. The SS prop that my brother runs on his 400 hp ski boat makes a huge difference as the SS prop is resists straightening out and retains its bite. I will have to ask him if he noticed any top speed changes as I always ask for him to slow down at about 60 mph - regardless of what prop he is using.

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    Moderator LuJon's Avatar
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    I will be switching to an SS impeller and a UHMW lined sleeve this year. I don't have any expectations on some magic improvements. I do expect some performance gains over the course of a trip though. Ultimately the cutting edges on the aluminum blades get dinged up very rapidly in the rivers up here and start to cavitate which costs A LOT of thrust! I expect the SS impeller to reduce this problem drastically. I have also hear that the UHMW lined sleeve handles rocks and other debris much better without gouging and negatively effecting flow. It also is supposed to provide some protection to the blades as well since there will be some give if a rock gets sucked up between the sleeve and imp. No way for me to prove up front that I am not blowing $$$ on nothing but I am thinking positive. I am also planning on contacting Karolds to get an OB stomp grate made. Boy how I look forward to not having to spend hours standing in creeks dropping jet foots and sharpening impellers! Well at least not having to do it as often!

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    Who sell the UMHW sleeve? Is that from Specialty Mfg? Maybe I need to look at a boat with a better load carrying capacity. It's only money, right?

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    Moderator LuJon's Avatar
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    Quote Originally Posted by beluga View Post
    Who sell the UMHW sleeve? Is that from Specialty Mfg? Maybe I need to look at a boat with a better load carrying capacity. It's only money, right?
    I looked at them at Greatland welding on the Palmer Wasilla hwy.

    I hear you on the load capacity... That said I don't think I can sell my old boat, just something about it

  9. #9

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    LuJon, maybe after your upgrade we can attempt Alaska_Lanche and LuJon vs. the Knik again. We have a score to settle so far we are 0 for 1.

  10. #10
    Moderator LuJon's Avatar
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    Hopefully we can get some high water and make that a reality!... I sure would like a pic of my boat next to that glacier. I will probably invite one more guy as well just to aid in the pushing...

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    My friends with 4 blades swear by them. I found that switching to stainless and a composite (instead of aluminum) sleeve made a huge difference for me. They do seem to have a better holeshot. A-1 Propeller and Impeller on post road have always been good resources for me.

  12. #12

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    Think I will go with the 4 blade stainless, I would like a stainless for durability anyway, so any performance gain would be a bonus. Will check out that composite sleeve too. Is that the UMHW?

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