powerhead intechange among '50s 7-1/2 HP engines?

[dodge trucker]

I have a 1953 Fleetwin 7-1/2 HP model # 7512 with a good bottom end. The powerhead ran but needed an overhaul (down on power, all carboned up)
I ran into a snag during the overhaul (will put up a separate post for that) but I just want to get this engine running again fo the time being; I have a leadon a (supposed) good powerhead from a Johnson AD-11 for what seems like a decent price; Can I put the AD 11 powerhead onto the #7512 lower end and use the Fleetwin gas tank, carb flywheel, and covers on the AD 11 power head? I want to use the reed plate or head from the Fleetwin

Oh and the "down on power" is in comparison to my Dad's Fleetwin 7512 that he has had for many years that has extremely low hours from new; not just "seems like"
I had both of these engines mounted on the same boat at the same time and ran them together and then each separately.

 

[HighTrim]

Sorry not going to happen. Whereabouts are you from?

 

[Chinewalker]

Nope, won't work. To many subtle changes between the first gen 7.5s and the later ones.

 

[dodge trucker]

I'm from Kankakee IL about an hour south of Chicago.

I was gonna put this in another separate post/ but now that I'm getting a few replies I guess I will add info about why I am looking to do this;
but before I forget what kind of "subtle differences" need to swap the '53 head or intake manifold onto the newer block or is there more to prevent this from happening? There are a couple of '51-53 power heads on feebay right now but this AD 11 was more reasonably priced and seemed like a more likely "drop on and run" (once I replace the coils, of course)

I want to get this motor running "for now," while I figure out what I did wrong when I put rings in the original power head;
It was a running engine/ but like I said, it was down on power and carboned up badly. Yes I did go thru the carb and ignition and had this engine running the best it could run as-it-was. I wish now that I had taken a compression test. this is not my 1st engine overhaul, but is my 1st outboard overhaul in a long time. (and 2nd ever powerhead job, though I have done a decent amount of carb ignition and lower unit work) Briggs, Tecumseh, Kohler air cooled engines, I lost count how many I have rebuilt; car engines too, I have done quite a few/ mainly conventional inline-6s and V8s.

Anyway enough about me. When I pulled this Fleetwin powerhead apart, I found the cyls within specs, and the pistons not scored, just all carboned up thoughout the exhaust tract, from the ports into the lower unit.
So I cleaned up everything I could and put it back together with new rings and gaskets. When I spin it over by hand something "catches/clicks" like there is interference keeping the crank and rods from spinning freely which makes no sense since this same block, crank, pistons and rods were together as a running unit for many years. I gave up on it for the time being and that was a couple years ago, it is time to get back at it.

My Dad passed away in '98 and when ever the day comes that Mom goes, Dad's Fleetwin will certainly be one piece that I am afraid there will be a "fight" for among myself and my older brother. if I can get this one that I have back running again then he can have Dad's. Currently Dad's motor sits collecting dust (but not hours!) Every time it eve has gotten started it has done so without issue

I will again have to source another set of all the power head gaskets and another carb kit as I do not want to reuse them even though the engine has not been fired since I put them in, just because of it having been a few years... At this point I can't guarantee that I still have all the gaskets I did, though I know that I have every piece to the motor itself.

1 more thing... I have seen posts that say to run 16:1 in these engines. We have always run 24:1 in Dad's. I have not lookd at it lately but I could swear that 24:1 was what it called for on the label on the flip door that covers the gas cap. I have never heard to run 16:1 before I seen it in a post here. I have heard that the newer oils are "reformulated" and that you can run 50:1 in these older engines but I can't say that I'm willing to try it....

 

[dodge trucker]

ok I found a guy that has a '53 7-1/2 HP power head for what seems a reasonable price so I can gt this motor back going again while I deal with that "original" powerhead issue just need to hunt down those gaskets