Champion Hydrodrive Year ID help needed

[bayham3261]

Hey everyone!

I just picked up a complete but definitely non-running Champion Hydrodrive. Based on the condition and Champion C7 plugs I’m assuming it’s been sitting in a shed for a very long time. I’ve always wanted to try my hand a fixing one of the unique motors. I want to see how slow I can make my boat go!

It is a twin model with the model/serial number is 4LHD 9344. The Old Outboard Book put this as a ’50 to ’52 model… either 7.9hp or 8.5hp. I’m assuming the serial number was sequential for the model so this would be #9,344 in production. I’m also assuming Champion made a lot of these back in the day so this was likely built in the first year of production…? so probably a 7.9hp…? Does anyone have serial #/production year info?

I can’t seem to find any differences in the limited info I have on champions that differentiates the 7.9hp from the 8.5hp. Was the differences just a hp rating adjustment on paper? If anybody has any technical/repair/parts diagrams on this… it would be appreciated. Thanks!

A little information is a dangerous thing!

[7tcu]

1950-51, 8.5hp-

[jcrigan]

I have been wondering what the differences were between the 7.9 and the 8.5hp motors. They are both rotary and reed valve engines. I have an 8.5 motor and on the rods there are a double row of roller bearings. There are a total of 64 rollers on each rod. Don’t know if the 7.9 is the same.

[frankr]

1950 was 7.9hp
1951-52 was 8.5hp.

Now you got me wondering where the extra ponies came from.

I’m looking

[frankr]

7.9hp had Scintilla magneto, 8.5hp had Phelon magneto. But I don’t think that should make any hp difference(?)

[frankr]

7.9 & 8.5 all share the same cyl head, reeds/reed plate, pistons, cylinder, and carburetor.

[frankr]

7.9 & 8.5 also share same con rods. crankshaft, intake manifold, and head gasket.

I’m running out of stuff to look at.

Could be spark advance on different magnetos (??)

[squierka39]

I had the 8.5 and 7.9 at one time. The head on the 8.5 was much thicker visually than the 7.9. My 7.9 is the 4K model, but I think it’s the same as the early 4L .

[bayham3261]

frankr wrote:

7.9hp had Scintilla magneto, 8.5hp had Phelon magneto. But I don’t think that should make any hp difference(?)

I’ve never heard of the Scintilla magneto… did a quick google search and saw that it was associated with Bendix…? I’ll have to pull the flywheel to check out what type of magneto.

I took a pictures of the head and it looks unusually thick to me… how does it look to you squierka39?

A little information is a dangerous thing!

[bayham3261]

here’s another pic…

A little information is a dangerous thing!

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