# 1952 Scott Atwater 7.5 HP Service Manual



## pcdimis (May 14, 2018)

Hello all,
I am in the process of aquiring a 1952 Scott atwater 7.5 (model 3325) and was wondering if anyone has any information on these? I am really interested in where to get ignition parts and a new impeller however I am not sure of the part numbers i need to cross reference.
Any help would be appreciated.
Thank you


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## Shaugh (May 14, 2018)

I have a manual I could send you. PM me an email.

I've done a couple..


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## pcdimis (May 24, 2018)

I was able to get the motor to briefly run in a barrell but stopped due to no water coming from tell-tale. I opened the lower unit and found the impeller was shot (new one on order). 
I was not able to run the motor enough to get any indication of where its at tuning wise but while working the speed control i noticed that the cam on the arm does not touch the carbuerator actuator until it is almost wide open and it barely moves the butterly at all?
Is this normal? I have read in the manual about syncronising the two but am not clear on the seetings or how to change it if i wanted to?


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## Pappy (May 24, 2018)

Usually the magneto will advance a bit before picking up and opening the carburetor. This is normal. On yours, without the manual, we would be hard pressed to tell you when to pick up the carb. 
Usually there will be marks on the cam that touches the throttle arm or roller that are used as a reference point. Check yours and see. 
Keep in mind this is generic information on my part. I only have one Scott engine, a 16hp.


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## pcdimis (May 25, 2018)

The manual i have states the following:
"When the speed control lever is moved towards the "Fast" position, the ignition timing is being advanced and the throttle opening must be increased at the same time. The correct synchronization is accomplished when the throttle shutter is just beginning to open when the center speed control lever has reached the position given in the tabel below. All measurements in the table are based on center of throttle lever and center of motor. " 
"Degrees retard (i.e. distance the center control lever shoudl be from center of motor towards "slow") at point throttle shutter begins to open."

Model - 503
Degrees Retard - 10
Inches on flywheel - 9/16"
Inches on Gas tank - 1-1/8"

So the way i interpret the above is the speed lever should be pointed towards the "slow" side 1-1/8" and the cam should be touching the carb linkage? 
However if you look at the photos i attached when it is in the center position I am a mile away from the carb linkag and dont see a way to adjust it? Plus i cant imagine someone trying to run this motor if it is truly that far out of adjustment?
Any photos/hlep from someone that owns this model would be greatly appreciated.
Thanks


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## Shaugh (May 25, 2018)

I guess it's not hard to see why they went out of business :wink: Mine had a mark on the cam where it was supposed to be when the throttle started to open.... See if you can find a mark.... you might have to take the gas tank off.... The cam is adjustable by loosening those screws on the bottom.

photos here might help. Mine had a punch mark on top of the cam:

https://www.vintageboatparts.com/shop/index.php?main_page=product_info&cPath=110_57&products_id=1609


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## pcdimis (May 25, 2018)

Thanks, 
I will pull the gas tank off this afternoon and have a closer look, hopefully I will have the new impeller next week so i can run it for more than a few seconds to able to perform some fine tuning.


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## Shaugh (May 25, 2018)

Have you looked at the ignition ? Those coils are usually disintegrated ? On a motor that old you will likely need to do it all...


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## pcdimis (May 25, 2018)

Yea I pulled the flywheel and it looks like someone has recently replaced the coils, points and condensors. 
The flywheel is also extremely clean, almost as if it was replaced as well.

The fuel system is the only thing that looks like it has not been touched since new. The gas tanks on these motors has a funky fuel cut off system that leaks horribly and i beleive I am leaking around the base of the vent tube so i have my work cut out for me getting it modifed and leak free.


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## Shaugh (May 25, 2018)

One thing I remember from mine is that Scott Atwater designed a float bowl drain that allowed you to drain after use.. just dumping raw fuel down the motor and onto the ground. it was commonly referred to as "the devils own device" because it leaked constantly and caused problems.... you might look into disabling that....

Another one of their great ideas.... like putting a 2nd impeller in a motor for the bail a matic.....


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## pcdimis (May 26, 2018)

Took the tank off and looked for timing marks and couldn’t find any. What I did notice was a price of wire that connected the main butterfly to the choke butterfly and it appeared to bind the throttle when I actuated it. I removed the wire and adjusted the set screw on the speed lever to enagage as soon as it moves from dead center towards the fast side hopefully that will at least get me in the ballpark when I get to run it.


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## Shaugh (May 27, 2018)

Ok, the manual does tell you the right relationship. The throttle lever should touch the cam when the center of the speed control lever is 9/16" on the flywheel before the center seam of the engine. I'd try to adjust it there and put your own punch mark for future reference.


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## pcdimis (May 28, 2018)

thanks for the heads up i have it set now to the 9/16" advance. i have a few gas leaks to tackle next 
, the fuel inlet elbow on the side of the carb looks to be leaking and the fuel shutt off on the bottom of the tank. 
I think im going to eliminate the fuel shut off and custom make a simple plate with a vent hole and a barb fitting for the fuel lime.


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## pcdimis (Jun 4, 2018)

got my new impeller in but am having troubles.

First thing is gas is running out of every possible path on the carb, i think the PO let it soak in a bucket of carb cleaner and it destroyed all the gaskets.


Second thing is no water coming from tell tale, i can put my finder over the hole and i can feel hot air.

Lastly i checked the compression and only got ~65lbs both cylinders (not sure how accurate those numbers are as i only cranked each cylinder 3 times).


the big thing im worried about is no water from the tell tale, with only feeling hot air co,ing out could it be a head gasket? riings? any ideas?


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## Shaugh (Jun 4, 2018)

Is the motor running in a barrel with water a couple inches over the plate? You need nothing less than that to evaluate an impeller.


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## pcdimis (Jun 4, 2018)

I had it in a 5 gallon bucket with water above the plate but not sure if it was a couple of inches or less


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## Shaugh (Jun 4, 2018)

So it was idling reasonably well but no water? Or was it struggling to keep going? If it was running reasonably then you should re-examine your impeller install.


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## Pappy (Jun 5, 2018)

Are you talking about "the plate" above the propeller? The cavitation plate? 
If so, you have to have water well above that. Think about where the water pump is and make sure the entire pump is completely submerged in your "test tank"


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## pcdimis (Jun 6, 2018)

The impeller on this model is below the plate, I am going to try and run it again this afternoon but gonna use 55 gallon drum to make sure I have enough water.


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## pcdimis (Jun 9, 2018)

ran the motor again in a 55 gallon drum and still no water, i pulled everything apart and blowed thru the lines and pulled the power head and blowed thru the water jackets and no blockages found. i put it back together ran it again and now im pumpimg water!

the only thing im a little worried about is that i could not find the gasket for the lower unit rear cover plate so i used RTV however when i tighten it down the prop gears lock up. I am assuming that the thickness of the gasket was factored in for the back lash setting so i pulled it apart applied more RTV and let it sit for awhile the re-installed it however i cant tighten the bolts as much as i would like or it lock on me again. gonna keep searching for the gasket.

if it doesnt rain tommorow i plan on trying the motor out to fine tune the carb settings.
Thanks to everyone for helping me get this thing up snd running.


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## nccatfisher (Jun 9, 2018)

pcdimis said:


> ran the motor again in a 55 gallon drum and still no water, i pulled everything apart and blowed thru the lines and pulled the power head and blowed thru the water jackets and no blockages found. i put it back together ran it again and now im pumpimg water!
> 
> the only thing im a little worried about is that i could not find the gasket for the lower unit rear cover plate so i used RTV however when i tighten it down the prop gears lock up. I am assuming that the thickness of the gasket was factored in for the back lash setting so i pulled it apart applied more RTV and let it sit for awhile the re-installed it however i cant tighten the bolts as much as i would like or it lock on me again. gonna keep searching for the gasket.
> 
> ...


 I would be pulling it apart and making a gasket, if not you are talking about a failure waiting to happen.


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## Shaugh (Jun 10, 2018)

Please post a photo of what you're talking about.... Not sure I understand where this gasket is...


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## pcdimis (Jun 10, 2018)

i came to my senses and went to the auto parts store and bought a roll of gasket material and made a new gasket. 

This is the cover I was talking about


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## Shaugh (Jun 10, 2018)

Wow that motor was 100% different in 1953.... Now I get it.... thanks...


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