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Thread: Replacement/Spare Prop: AL/SS, Pitch? OMC 9.9

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    Default Replacement/Spare Prop: AL/SS, Pitch? OMC 9.9

    Another prop and prop question folks. Searched around the site and read a lot, but ultimately didn't find an answer for my situation.

    I want to buy a replacement or spare prop for the Johnson 9.9 2-stroke on my Grumman Sport Boat, and I'm not sure what prop and pitch to buy. The prop that came on the engine is a 9-1/2 diameter with a 10 pitch. The engines runs good (no real idea of the RPM's, but it sounds good), and pushes the boat 10 mph with 600 pounds in it. I have no idea what it will do if/when I load it on up closer to 1000 pounds.

    Obviously, I need a spare prop for safety/reliability reasons. I'm wondering if I should just buy another of what is on the engine now, or buy a prop with a different pitch for heavy load situations. (I'm not even sure that will work. If I break the other prop when lightly loaded, won't hte "heavy load" spare prop just lug the engine down anyway?)

    The other issue is I would like to go to a stainless steel prop and that be my main prop. I could just buy a SS prop same as what is on there and have the old AL prop as a spare, but that eliminates the ability to have a "light load" and a "heavy load" prop. Yhen again, with a stainless steel prop, do I even need a spare prop?

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    PROPS::: the SS props look good never purchest one, just used the AL ones , they work fine till they hit the rocks in the streams I was running,
    went with 3 props a new one for the lakes , #2 for big rivers an # 3 for the thin water streams, an neaver throw a prop away, it can get you back
    home ,I have a few worn down but still go [ for thin water ] have had hubs go bad [spin out would not hold, just slip ] have had a blade or 2 break off [ 2 many rocks] always had a file to trim them up a little never lasted that long, SID
    PS the rubber bushing in the prop can be replaced but you need special tools the average person don't have access too,

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    Quote Originally Posted by Sid View Post
    PROPS::: the SS props look good never purchest one, just used the AL ones , they work fine till they hit the rocks in the streams I was running,
    went with 3 props a new one for the lakes , #2 for big rivers an # 3 for the thin water streams, an neaver throw a prop away, it can get you back
    home ,I have a few worn down but still go [ for thin water ] have had hubs go bad [spin out would not hold, just slip ] have had a blade or 2 break off [ 2 many rocks] always had a file to trim them up a little never lasted that long, SID
    PS the rubber bushing in the prop can be replaced but you need special tools the average person don't have access too,
    After reading this I assume you need different props form different waters? Or is there a jack of all trades prop? If multi are going to do most of your running in smaller sloughs and lakes but crossing the
    migjty yukon what should you go with?

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    Well, there is no such thing as a prop that does everything at top performance. Anytime yo go with one prop for everything, you have to compromise something somewhere. (That's true for most things.) And I'm okay with that. I would be fine with a compromise prop that pushed the boat maybe not at the highest speed possible when empty or when pulling my son on an inner tube and maybe it burned some more fuel and was a little slower puhing me and a moose up a river as compared to different props pitches specifically for those purposes. To be honest, I don't really know what pitch that compromise prop would be. Perhaps the 10" pitched prop I have IS that prop. For this engine, on this boat, I don't know.

    I'm not really concerned about what body of water I'm on; I'm mostly concerned with performance at different weight loads.

    That said, if I have to have two props (a main and a spare), shouldn't one be fore pushing the boat fast when lightly loaded and one be for pushing the boat when heavily loaded? In this way, the props each do double duty in that I always have a spare on hand. To play devil's advocate, which is your main and which is your spare? If, most of the time, I'm camping or hunting fom the boat, then, most of the time, it is at leat moderately loaded, so should I just get one prop for a loaded boat (7 or 8 pitch perhaps?) and just keep the current prop as a spare?

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    Quote Originally Posted by Sid View Post
    PROPS::: the SS props look good never purchest one, just used the AL ones , they work fine till they hit the rocks in the streams I was running,
    And that's why I want to go to a stainless steel prop. I grew up with a boat that ran SS, so that's what I know as "the best."

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    Folks out where I used to live shunned SS. Said that they would rather bend aluminum than tweak a shaft. That was the theory anyway. I've owned both. I run aluminum on my 9.9.

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    With your 9.9 you won't notice a difference with prop changes. Stainless is fine if you don't have shear pins. I use aluminum for ease of truing up and cost.
    Now left only to be a turd in the forrest and the circle will be complete.Use me as I have used you

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    Quote Originally Posted by sayak View Post
    Folks out where I used to live shunned SS. Said that they would rather bend aluminum than tweak a shaft. That was the theory anyway. I've owned both. I run aluminum on my 9.9.
    I've read this theory elsewhere in various internet forums. It is a plausible theory, but I assumed the purpose of the shear pin was to be the sacrificial link in the drive train, not the propeller.

    Quote Originally Posted by Amigo Will View Post
    With your 9.9 you won't notice a difference with prop changes. Stainless is fine if you don't have shear pins. I use aluminum for ease of truing up and cost.
    I do believe it is a shear pin motor. Not sure why that makes a difference, given what I said just above. We ran a stainless prop on a 90 hp and hit bottom a lot without breaking a pin, HOWEVER, that was Florida soft bottom lakes, not interior rivers with gravel bars and floating logs.

    I've blended nicks in both. True, an aluminum prop is easier to file and blend, but I've noticed that the nicks in a stainless steel prop are usually much smaller/shallower than those in an aluminum prop and therefore require less blending in the first place.

    Stailess is usually MUCH mre costly than aluminum, however, for a 9.9 it's just less than double the cost (so only about a $60 difference.) Then again, $60 is $60 and that money could be used elsewhere.

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    have not purchest props for a few years but the differance is a lot more than $60 as you will be working a lot of shallow water you don't want sheer
    pins in the prop it will break at a time when you need the motor thr most , an if you do lots of running the thin water the drive shaft on gear box will break, neaver had the shaft on the gear box go but the maine drive shaft from the motor to the box has broke on me [ lots of rocks ]
    the 9.9 / 10 HP OMC should not have a pin there is a slip clutch [ rubber bushing in the prop ] SID

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    Pulled the trigger on a direct replacement 9-1/2 x 10 pitch aluminum prop from Michigan Wheel. $125 shipped UPS 2nd Day Air (only option available) and that includes a floating a prop wrench, spare prop nut, spacer and 10 cotter pins. I'll find a home for it in the boat someplace out of the way.

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    I did away with the cotter pins an went with a locking nut, got my locking nut fwom Lows an it is a stanless nut I think , Alaska mining an diving is where I got my props, there is a plastic washer that is keyed for the prop shaft , do keep an exter one with you , I have droped the hole gear
    boxes in the field , you should also look at the water pump an have spear parts on hand out there , take it apart to know hor to repair it on the river .
    if you need some help call 677-0205 Anchorage SID

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    Most outboards come with general purpose prop on them. If you are using a light planning hull, a bigger bite will work better, if loaded heavy and no possibility of planning, less pitch and bigger dia is better. For different waters/loads the GP prop is a good choice. With a small motor and a displacement hull you won't notice a lot of difference in props unless you get too radical on pitch or diameter. The stock prop is a good choice for all around use.

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    rbuck351 said it very well I think, you can;t get blood out of a stone , you will never see the differance on going up a stream or across the lake ,
    you should see some of the props I have used an still use in the thin water streams SID

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    Quote Originally Posted by rbuck351 View Post
    Most outboards come with general purpose prop on them. If you are using a light planning hull, a bigger bite will work better, if loaded heavy and no possibility of planning, less pitch and bigger dia is better. For different waters/loads the GP prop is a good choice. With a small motor and a displacement hull you won't notice a lot of difference in props unless you get too radical on pitch or diameter. The stock prop is a good choice for all around use.
    This pretty much fits what I have read.

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    my experience with many canoes and different pitch props, was that if you went with a slower pitch than what came on the engine, you do nothing to increase load hauling capacity, yet your cruising speed is notably reduced. You will hear the motor gaining rpms, but doing nothing else significant. when you go one size faster pitch than what came on the engine, you get better cruise speed with the motor LIFTED, which really matters. Usually, what came on the outboard is sufficient for canoe hulls.

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    Quote Originally Posted by mainer_in_ak View Post
    my experience with many canoes and different pitch props, was that if you went with a slower pitch than what came on the engine, you do nothing to increase load hauling capacity, yet your cruising speed is notably reduced. You will hear the motor gaining rpms, but doing nothing else significant. when you go one size faster pitch than what came on the engine, you get better cruise speed with the motor LIFTED, which really matters. Usually, what came on the outboard is sufficient for canoe hulls.
    Looks like I made the right choice then. My knowledge of bass boats doesn't transfer well to canoes LOL. I took an opprotunity to teach my son ho to change a prop today while test fitting the new spare prop on the 9.9.

    Incidentally, I recently bought a new, old stock, spare prop for my '69 4 hp, but it's the wrong prop. Once I figure out what it really is, it will be up for sale or trade here. I also have a prop for a 9-1/2 to unload. But that's a different story.

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