Topic: 1947 7.5 hp Scott Atwater – Antique Outboard Motor Club,Inc

This topic has 12 replies, 5 voices, and was last updated 4 years, 4 months ago by Geer Pyron.

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August 11, 2020 at 10:15 pm #211373
Geer Pyron
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I’ve been working on a 1947 Scott Atwater recently and discovered that there is not much information out there on the inner web. Does any one have a manual or parts list?
I suspect I’ll have to make or buy a water pump cam but do not have the specific part number for it. That makes going it more difficult.
Or, is the cam integral to the drive shaft, hence I have to get the drive shaft too?
The cam is held on to the drive shaft by tension alone.
No key or pin.
Any suggestions?
Here is a picture of what I’m dealing with thank you.
G

JMGP
- This topic was modified 4 years, 5 months ago by Mumbles.
August 12, 2020 at 9:03 am #211404
Buccaneer
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US Member
Not sure if this is your lower unit, but I see it list the “cam and driveshaft” as one,
so I guess it wasn’t meant to come apart.
Is your cam too worn to work the impeller properly?
There are probably some machinist that could find a “fix” for that cam.

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August 12, 2020 at 9:08 am #211411
frankr
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3.6 or7.5hp? I do have the parts lists. Anyhow, it looks like you will be making a cam. They were integral.
August 12, 2020 at 1:14 pm #211433
Geer Pyron
Participant
Thank you both for the input. I’m going to wait till the rotor arrives and then install and test it before resorting to my previous MO of tearing everything apart before knowing anything about anything.
If it doesn’t pump, I’ll move on with your other suggestions.
Thanks again.
G

JMGP
August 12, 2020 at 2:35 pm #211439
Buccaneer
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US Member
Frank, just curious, how would you go about making that cam,
and attaching it to the driveshaft?
I’m guessing I’d have a hard time doing an eccentric on my lathe’s
three jaw chuck. Suppose one could just turn the brass to diameter
then resort to the drill press to drill off center.

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- This reply was modified 4 years, 5 months ago by Buccaneer.
August 12, 2020 at 5:20 pm #211457
frankr
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It would be easy with a 4-jaw chuck. The drill press idea is ok too. I guess the amount of offset is the main question.

I suppose the original was shrink fit to the shaft but can’t swear to that. Anyhoo, I’m a Locktite junkie. That’ll hold it to the shaft. And easy.
August 12, 2020 at 6:28 pm #211463
dave-bernard
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US Member
how about make a sleave on the cam?
August 12, 2020 at 6:36 pm #211466
Buccaneer
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Sounds like I need to spend one of my SSA check on a four jaw chuck.
A brass sleeve could be silver soldered on the old cam, but there again,
a four jaw chuck would be handy to machine the worn cam first!

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August 13, 2020 at 6:47 pm #211574
Geer Pyron
Participant
I’ve mulled over all of the ideas above. The sleeve would be the first try. If I fail at that Ill try making a new cam. I do have access to a lathe with a four jaw chuck but I don’t have experience with lathes so the drill press option will be my first try. If it comes down to it.
As far as the offset goes, the cam seems worn fairly uniformly so I’ll just take some measurements from it, pretending there is another 32nd all around it’s diameter (?).
But, how crucial would all this be? Would pumping efficency be that effected by the 32nd” lost on the cam (maybe even less than 32nd)?
Anyhoo, I’ll try to keep y’all posted.
G
PS I did start the motor the other day, sans gearcase and such. I couldn’t help myself. It’s the first time that one of my projects started on literally (sorry to anyone out there who has a 15 year old for using that L word) the first pull.
Of course I immediately shut it down once I knew it would run.
G

JMGP
August 13, 2020 at 8:43 pm #211577
frankr
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The main goals are that the cam fit the I.D. of the rubber rotor and that the rubber rotor touches the pump cavity as it goes through it’s wobble action—-that is determined by the offset.
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