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Thread: B utility/Johnson oakland prop depth question

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    Default B utility/Johnson oakland prop depth question

    I have a 1950s style 11ft B utility. It looks a lot like a FooLing or a sid craft. Its much the same in design all the way. With my stock Y80 and factory prop, she will run around 50 on a good GPS reading. What I am trying to do is to get out my 6NHR HotRod, original carter carb and phelon ignition on it and set it up like it was originally intended for. I found a nice two blade Johnson Oakland prop that I believe is an elephant ear style, and about 11-12" pitch x 7" diameter. If anyone ever seen the pic of a Champion HotRod outboard on the Fritz Deziegn manufacturing website, you will see the identical prop on that motor. It is that kind.
    The question I have is either how deep these props were run or rather what transom height was generally set for starts. I'm sure that some 20H mercs had these propellers run on them on some of the old Hal Kelly and/or SidCraft runabouts. I just don't think that they ran these as high up as todays props, but I'm not sure. There is no lip or cupping on any of the edges. It is an interesting propeller on its own and has a trowel design of its blades to channel water I can only estimate. I don't think that they would have been all that successful though. It seems no one followed that design later on afterwards. If anyone knows about how these were run, let me know! Thanks!

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    Team Member zul8tr's Avatar
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    Back in the days of Hal Kelly B class race boats transoms were about 13-3/4" for his Fooling, Airborne, Wetback and Jupiter. The KG7H and 20H engines measured about 16-3/4" (18-3/4" with Q tower) from the rear center of the prop shaft up to the top rear corner of the clamp that sits on the transom (with NO shim sticks). As a result with NO shim sticks on H tower the rear prop shaft center was about 3" below the bottom with prop shaft set parallel to the rear bottom planning surface. Assume 1/2" of shim sticks the prop shaft rear center was about 2-1/2" below the bottom. That is fairly deep compared to where they were run in the 70's when I raced my Wetback hydro depth was about 1" to 1/2" below the bottom depending on prop and water conditions. I had letter correspondence with Hal Kelly in the 70's and he came to one of our races in Region 5 and was amazed how high I was running a 2 blade SS the prop on his Wetback hydro as well as how high all the race boats were running the props compared to when he raced in the 50's.

    With the Y80 on your utility runabout it can do much better than 50 if you replaced that factory bronze prop for a much better SS prop and jacked up higher and dialed in the set up. Cooling is an issue on the Y80 if too high so as a start shoot for 1" below bottom for the prop shaft rear center with shaft level to bottom, go from there with up & down, kick in & kick out as needed for proper running trim with no porpoising. Using the factory prop I assume your engine still has the factory metric prop shaft? If so that needs to be replaced with a 9/16" diameter shaft for the numerous SS props available. I run the Y80 on my hydro at 1/2" below the bottom with 3 blade SS round blade prop and no cooling issues.
    " Three may keep a secret if two of them are dead" Ben Franklin

    Location: SW Orlando, Fl

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    Quote Originally Posted by zul8tr View Post
    Back in the days of Hal Kelly B class race boats transoms were about 13-3/4" for his Fooling, Airborne, Wetback and Jupiter. The KG7H and 20H engines measured about 16-3/4" (18-3/4" with Q tower) from the rear center of the prop shaft up to the top rear corner of the clamp that sits on the transom (with NO shim sticks). As a result with NO shim sticks on H tower the rear prop shaft center was about 3" below the bottom with prop shaft set parallel to the rear bottom planning surface. Assume 1/2" of shim sticks the prop shaft rear center was about 2-1/2" below the bottom. That is fairly deep compared to where they were run in the 70's when I raced my Wetback hydro depth was about 1" to 1/2" below the bottom depending on prop and water conditions. I had letter correspondence with Hal Kelly in the 70's and he came to one of our races in Region 5 and was amazed how high I was running a 2 blade SS the prop on his Wetback hydro as well as how high all the race boats were running the props compared to when he raced in the 50's.

    With the Y80 on your utility runabout it can do much better than 50 if you replaced that factory bronze prop for a much better SS prop and jacked up higher and dialed in the set up. Cooling is an issue on the Y80 if too high so as a start shoot for 1" below bottom for the prop shaft rear center with shaft level to bottom, go from there with up & down, kick in & kick out as needed for proper running trim with no porpoising. Using the factory prop I assume your engine still has the factory metric prop shaft? If so that needs to be replaced with a 9/16" diameter shaft for the numerous SS props available. I run the Y80 on my hydro at 1/2" below the bottom with 3 blade SS round blade prop and no cooling issues.

    Thanks! I will try that. I have a Hopkins SS round ear 7" diameter. But it has a really high pitch and boggs my Y80 down at 6200-6400 rpm and mid 40s speed. My Champ HR cant get above idle with that prop starting in water. The thing is, on this boat, I had it at about 1.5+" deep with both. If I ran it at 3/4 with the Y80 it might run more free to about 7000rpm and 52-54 mph or so, hopefully with the Hopkins wheel. It is stamped EVR 16:21 on that prop. My boat also did porpoise really bad with the heavy motor, so I made some strong adjustable aluminum after-planes and it vastly improved. When I put the factory Y80 prop on, it jumped to 8000+ rpm and gets 50 or so, but hard to read going so fast on my gps. I will set my Champion HR motor at about 13.5" transom height with the Oakland wheel when I try it on the boat. I'll try to get some pics of my rig on this thread in a week or so when I get it set up. The boat is like a SidCraft, FooLing, and a speedliner all in one. Its one of my creations.

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