Crankcase cylinder assembly question

[Maverick70]

I've had a 2007 70 TLR for about 8 years. It's always been reliable and run strong. However, a few years ago while replacing the thermostat, I noticed bad corrosion to the aluminum case where it holds the thermostat. I always flush it, but didn't know to check the thermostat before then and didn't know how it was maintained by the previous owner; lesson learned to always check and clean this weak spot. The end result was a pea sized hole that I patched with epoxy. The epoxy works, but I really want a long-term fix. Most welders I talk to won't touch motor aluminum. Is it the general consensus that welding this is not likely to work?

I see that part number 6H3-W0090-441S includes the crankcase, head, and crankshaft piston assemblies with oil pump for around $2300. Does this mean that these parts are already assembled as a powerhead ready to drop onto the lower unit and attach the old cables, starter, carb, etc. Or, does the crankshaft piston, head, pump, etc need to be assembled into the new case by the user first? If it's assembled, this seems like a decent long-term option with less labor than just replacing the case. If I were to replace the crankcase and use the old crankshaft, then I'd want to replace the pistons anyways. Am I understanding this correctly?

I have modest mechanical experience. I have basic tools and have rebuilt a motorcycle motor, but no formal training. Would replacing the crankcase assembly require any specialized expensive tools?

Thank you,
Keith

[TownsendsFJR1300]

I've had a combo/head cylinder (on a merc) many years ago with a hole rotted thru the water jacket to the combustion chamber.

I cleaned up the corrosion, made a plug of aluminum to fit nicely and had it heli-arced in. Worked great! Any good aluminum welder can do it..

Your epoxy fix is fine, been done many times by members in the same area.

Anyway, that long block would come assembled.

[Maverick70]

Thank you. I'll try to get it welded first.