shaft is stuck in the crank shaft

[clint96940]

Hi everyone,
I am working on a 2006 Mercury 3.3HP (Model: 1003201FK, Serial No: 1B574117). It ran flawlessly for over ten years, but I pulled it apart to replace a worn-out rubber impeller.
When I dropped the lower unit, the driveshaft slipped out of the lower gearcase splines but stayed permanently frozen solid inside the powerhead crankshaft splines due to heavy brown rust.
My main problem: The plastic water pump housing is completely loose and slides up and down the shaft, but I cannot remove it or drop a new impeller down from the top because the shaft won't budge. I also cannot get the new impeller pin and housing reinstalled from the bottom because there is physically not enough room inside the midsection leg casing to work with tools or my hands.
Important constraints:

1. I do not have access to any local replacement parts or a new crankshaft oil seal, so I cannot use high torch heat or methods that risk destroying my only working oil seal.
2. I have a second backup engine, but its powerhead block is completely frozen/seized and unusable.
3. I have already tried heavy WD-40/brake fluid overnight soaks, a slide hammer, building a washer-and-nut wedge press with chisels, and a heat gun on high with a wet cloth protecting the seal. It has not moved a single millimeter.

Since the shaft is permanently fused to the top block and cannot be removed without ruining the seal, is there any known workaround to get the new impeller on and get the water pump housing bolted back down with the limited space inside the leg?
Any advice from the experts would be greatly appreciated. Thank you!

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[Chris1956]

You can open the crankcase and remove the crankshaft and driveshaft as a unit. Now you can heat and pull them apart. You can probably put an oring on the driveshaft to act as a seal or just use heavy grease on the driveshaft.

Also, heating the driveshaft and then spraying with a penetrating oil, in cycles, help pull the oil into the crankshaft splines.