Hello Phil
I'm similarly in the same boat as you are but with a vintage automobile. It has a cylinder head that was cracked due to freezing. I came across two sites which advertise materials for the repairing of engine blocks.
a) Muggy Weld which supplies welding rods for repairing cast engine blocks. Illustrated on their site is the repair of a CASE backhoe engine block with a 1 1/2 inch hole, caused by a thrown rod repaired with their welding rods. According to their ad, no great expertise in welding is required to carry out these repairs.
Link
www.muggyweld.com
b) Loctite supplies a 2 part epoxy called Steel Putty and they can be reached at
www.loctite.com
I did contact a representative at Loctite and explained my problem and he recommended the above product. I haven't tried either product but will probably go with the Steel Putty.
Goodluck in your repair and let us know how you make out.
Regards Ted