I'm sorry for you and your grandmother's loss...

If you really want to get rid of it cheap. Take the cover off, give it a cleaning and take a bunch of photos. Find out all you can about the make and model and then post it for sale or an add for a free boat and trailer. My guess is that the boat may have a good reputation. It may be why your grandfather decided he wanted to restore it. Someone else may feel the same way!

You could even post it up here to see if anyone knows anything about it. Some boats have support groups where you'd get good advice and maybe an interested party.