KG7 Impeller Question

[Aidan Smith]

I have both a KF and KG-7 in my current collection. My KF7 has a standard lower, and my KG7 has a B Quicksilver lower.

Do these share an impeller? If so, does anyone know who is currently producing them?

If not, what’s the difference?

 

Thanks

"Shells sink, dreams float. Life's good on our boat."
1921 Elto Light Twin F
1950 Mercury KF-7
1951 Mercury KG-7
1959 Mercury Mark 6A

[green-thumbs]

Mercury Parts Catalog shows KF7, KG7 & KG4  use same impeller Part#47  21164

Non Standard gear cases Q MAY use a different impeller,

Louis

[A. Hoskins]

Green Thumbs is correct and his list should include the KE-7 as well. The quicksilver racing lower units use a (obviously) smaller diameter impeller.

Certified JB weld

[fastjohn]

No.  The KE-7 is different.  It is the same as the KE-4 and Mark 7.  Impellers are available for the KG/Kf-7, or you can use a Sierra 18-3051 or OMC 395289 and reduce the height or thickness.  The other dimensions are the same.

[green-thumbs]

KE4/Mark 7 & KE7 have 9/16 prop  shaft

KF7 KG7 & KG4 have 5/8 prop shaft

[A. Hoskins]

Oops, I stand corrected.

Forgot about the prop shaft diameter.

I’ve modified the 5/8 I.D. impellers to fit the smaller shaft.

Certified JB weld

[fastjohn]

Did you use a bushing?  Source?  Picture would help.  Thanks

[Tubs]

I got one one those impellers and sanded it down but decided not to use it. Those raised portions are meant to make a seal against the cover and inside the cartage so I feel the thickness does matter.  I think I got the thickness OK. The problem I have with this modification is you end up removing all the rubber from the brass center. Now the brass is in contact with the aluminum, no mater way which you face it. I couldn’t come up with a way to remove some of the brass from the center, so I sent a couple of bad impellers to Brian. I take them out while changing the gear lube when I’m done running one of these motors for the season. They’re really easy to get at on these.  

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[A. Hoskins]

Good point. I agree that the raised portions as shown do have a function but I don’t think they are absolutely necessary.

When I reduce the section height of the impeller I also cut back the brass center with a Dremel using a bit that kinda looks like a little end mill. It is time consuming. The water pump covers are easy to refinish – the cartridge, not so easy, mostly I don’t bother.

The difference between the 5/8′ and 9/16″ shafts is approximately .06″. I use .03″ (same approximation) brass shim stock epoxied in place and cut to clear the pin.

Just seems to me that the impeller spinning around in the cartridge at a thousand RPM doesn’t require a real precise fit.

Certified JB weld

[Author]

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