Trying to help out a future prop maker

[tim king]

I'm trying to help a guy who has a mark 58 mercury. He said it had the stock lower unit on it. So he got a different tower housing. And put on a Yamato lower unit. He's got an old D stock hydro. But he doesn't have a prop. The lower unit is off a 302. He goes to Oregon State University. He wants to start making propellers. So I told him I would help him out and send him an old 45 prop. And an old two blade Yamato prop. Does anyone have any information on this subject? This is just going to be a river runner. I know there's a couple things in question here. What kind of water pump will he be using? And will a small 45 prop with a shim even fit on a Yamato lower unit. And will that gear ratio even work?

PS I will direct him to this website. So hopefully someone in here can help him out.

[krazy karl]

First of all what is he using for a tower? I have a similar project going but with a stick tower.
kk

[tim king]

OK Karl I directed him here so he can tell you what he is using for a tower.

[PRO-MOTIONRACING]

It will work great. I ran this combo for 10 years. I feel the trick is to use a new gearcase not an old worn out one. The 9/16 shaft is to small and the bushing to thick, the pin will fail. The stock shaft (with a bushing) and shear pin work, just replace the pin a lot, like every heat and use a nylon washer in front of the prop just in case as to not tear up the cone.
The Yamato gearcase has no top seal so your adaptor needs a seal. I found a seal that fits the gearcase and cut it down to fit without sticking out the top but it was very thin and I have yet to try it. If someone needs the number for that seal let me know I will dig it up.
As for props, D- Stock props work great and you can find two blades around cheap. Local machine shops will be able to cut the slot in the front for the shear pin, usually about 30.00 My thought has been, the Yamato case is one tooth under but with a little porting the RPMs are up so it all works out.

Good Luck, 50-R

P.S. A piece of 3/8 metal tubing (fuel line) bent into an "L" shape just below the bottom of the boat as a scoop will give you more than enough cooling.

[bill van steenwyk]

FYI it would not be necessary to replace the shear pin every time if you use a titanium bolt or rivet for a shear pin. I have several that I used in the 70's on a 500CC Konig and continued to use on an RB that put out 85-90HP. I still have several in my tool box, bent slightly yes, but still good and serviceable and used for testing and racing for over 20 years. If you wish they are available new from Steve Litzell who is the Konny/VRP dealer, or you can purchase from any aircraft service center. Just be sure and ask for a titanium or similar material rivet or bolt the right length and diameter.

[tim king]

That's just what we needed to here. I thank you very much. And thanks to these forums. Cuz that's the kind of information you can't get just anywhere.