Really Confused with Scott Atwater Impeller P/N

[drifter]

I’ve got a 1957 (model 3375) Scott Atwater 7.5 hp. I’m totally confused by the part number for the impeller. Research leads me to p/n 3755-5100 or 3785-5100 or MC3755-5100.
Some photos show 6 vanes. Some photos show 10 vanes. Some have larger diameter center sections. Some have ribs on the center section.
I am totally confused. What is the correct p/n for my 57 Scott Atwater 7.5. (not a gold and green hood, but a red fiberglass hood.)
Also, is there a substitute impeller from another manufacturer. Somewhere I saw a reference to a Honda impeller, but I don’t know a part number for the Honda.
Does Sierra make a substitute for the Scott impeller?
Thanks for the help.

• This topic was modified 2 years, 3 months ago by drifter.

[frankr]

I don’t really have the answer, but I do know that 3755-5100 fits up thru 1956 with the water pump up below the powerhead.  Does your 1957 have the pump down on the gearcase?   Sorry, I don’t have the parts book for that one.

 

EDIT:  From what I’ve been able to dig up (not reliable) it appears that 1957 still had the pump under the powerhead.  If that’s true, 3755-5100 is the correct impeller.

• This reply was modified 2 years, 3 months ago by frankr.

[drifter]

Thanks Frank. Yes, mine has the impeller just below the powerhead.
I have the 57-58 Scott Atwater and Scott Outboard Service Manual and on page 217 it shows the pump assembly for 57 – 58 models 5, 7.5, 10, and 16 hp.
The service manual does not show part numbers but from the drawing and write up description, 57 and 58 must use the same impeller for the above listed models..
Still confusing though as some Ebay sites show a 10 vane impeller kit with “O” rings..
Somewhere I’ve got information about a guy who is an AOMCI member and he rebuilds the core for these impellers.
As a side note…..if I choose to not use the bail-o-matic feature, can I get by with not replacing the upper impeller or simply leaving it out all together?
Thanks again.

[Buccaneer]

Prepare to be boarded!

[Buccaneer]

Here’s some notes from others, I had saved in my files———
—————–
I would like to know where to get impellers also for a 7.5hp bailamatic.
I have used a honda impeller part number 19210-ZW9-013 I had to shim the
housing with 1/16 inch stainless and also shim the impeller to the shaft.
I am getting ready to fix a Firestone that was made by Scott I believe and
it would be nice to purchase the impellers if someone knows where to get them?
I only shimmed the top impeller using a honda impeller on the engine I re-did
since the lower one runs the bailamatic I didn’t re-do it. You can see it
run here. I did send an email to flying scott but didn’t get a response.
Thanks for the help.

Joe
=========
Re: Scott 10 hp where is water pump
Postby Mumbles » Tue Jul 05, 2016 9:34 pm

cannuck wrote:
Is it necessary to replace both .

Not unless you want to use the bailer option.
I think some guys have tried it by removing the one
impeller but for this ’56 7.5, I made up an aluminum
hockey puck to fill the bailer impeller cavity and plugged
all of the unnecessary holes. Now it runs cool and pumps
like a fire truck.
=================
I ran across this inexpensive, readily available Honda impeller
that is supposed to fit the Scott Atwater Bail-A-Matic 7.5hp.
Just passing along the info. Curious to find out if it works:

Honda 4-stroke 8hp 9.9hp BF8D BF9.9D
19210-ZW9-013
Number of Blades: 6
Plastic Hub
Height: 14.77mm
External Impeller Overall Diameter: 45.04mm
Internal Shaft Insert Diameter: 13.35mm
==============
Ron Hawkins used Honda 19210-zw0003 impeller
Ron Hawkins I just removed the original liner
and the modified the inlet and outlet holes on
the 9.9 Honda liner and epoxied it into the S/A housing.
===============
Ron Prochaska
Author
Tony C Zamp only problem I’ve had so far on the 5th dry
start the factory drive pin is too small. It slipped.
I used a 6/32 stainless bolt and enlarged the slot on the
impeller. Had 3 more dry starts no issues I’m torturing
this to see how well it will handle the housing being up
so high. So far this is better than old nos impellers I’ve
tried in the past. I have not wet them before starting once.
I’m sure if you wet before starting you will have no problems
ever. As if now I’m ready to put it on my boat
=================
Jason Pickerell
I don’t understand how that impeller works by itself, but it
seems to, and many people have said that they did the swap.
When I mocked it up in the housing on my engine, the height
was great, but when I lined up the center bore of the impeller
with the center of the hole through the housing, the blade tips
didn’t quite touch the vacuum side of the housing. Maybe it’s
working good enough as a slosh pump on that side IDK.
I wound up epoxying the liner from the Honda inside the Scott
Atwater housing and die grinding holes in it. Once assembled,
and run, the tell tale stream was like a water jet!
=========
Ron Prochaska been there done that honda thing.. Works great
if you can add .064 to the ID of the housing and polish the
bottom..you remove the incert then turn a aluminum ring to
id .064 od to fit the housing… Bingo the small honda will do
it but it took me one whole winter to convert the damn thing
way back when
==================

Prepare to be boarded!

• This reply was modified 2 years, 3 months ago by Buccaneer.

[frankr]

Club member Brian Wilcox is the guy that casts new impellers on your old hub.  I don’t know if he does S/A though.

Call 810-794-7685 before 8 pm est please.  Or email Baron0418@att.net. please note the b must be a capital.

[drifter]

Buccaneer, I see from the chart you provided that the 3755-5100 impeller covers models 3355 and 3365 but not my 3375. Odd that the 1955 and 1956 models are listed but not the 1957 model. Could this be because McCulloch purchased Scott that year. I’m guessing the 3755-5100 impeller would surely fit the 1957 model 3375 motor.
BTW, has anyone tried the impeller “kits” (10 vane impeller plus “O” rings) listed on Ebay?
Thank you for the information.

[frankr]

OK, I’ve done some more digging.

The chart above was printed before 1957, so it makes sense that 1957 is not included.

I found the 1958 parts book for model 3385.  It still uses the high mount pump and 3755-5100 impellers.  So, 1957 surely would be the same.

1958 was the year of the change to McCulloch.  The 1958 McCulloch was model 133 and had the low-mount pump and different impellers.

Hope this clears it up just a tad, maybe

[frankr]

One of the e-bay sellers is Discount Marine Parts.  I have never purchased anything from them, but they are pretty well known.  Let us know what you find out, if you do.

[Buccaneer]

Frank, thanks for clearing up the chart. I’m going to add your info as a footnote to my chart!
I’ve purchased head gaskets for Scott 3.6 hp motors this summer from Discount Marine’s Website
and the transaction was good!

Prepare to be boarded!

[Author]

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