Maybe I found the answer. Would you use a small circular saw. I see one for sale, Mastermind 3" and also a Makita 3 3/8". Has anyone used either of these.
Thanks for any information.

There are two options for a power tool; a biscuit jointer has a small-diameter circular blade and can be set and jigged to give a perfect plunge cut into the face of one floorboard. Since it can't cut all the way through a 3/4" board, the rest has to be chiseled, but if you are careful you can avoid marring the nice start of the cut.
Second tool is a Fein Multimaster (or the generic equivalent) This uses a vibrating/oscillating blade to plunge cut as deep as the blade will allow. It takes more skill to start the cut with this tool, but there is no chiseling required. Would be an ideal companion to the biscuit jointer which would start the cut perfectly, and the Fein would make quick work of the remainder.
A router with a flush-cutting bit and a guide can be used to clean up a cut, but it won't reach completely into the corner, so a chisel is indispensable.
Casey

Thanks, Casey, The Fein Multimaster looked really nice on Utube. Found one on Amazon.com. I would have to make sure I got the set that would include the square woodcutting blade? The kind of round on top and pointed on bottom would work too? They had different choices of attachment blades.

thanks for the post I am also looking for some good answers as I have no idea about it....

I am getting lost in details as far as the multi tools. Today have been looking at reviews on Amazon.com for the negatives. Dremel is noisy, gets hot after 5 minutes, bit comes loose. Price $119.
Rockwell heavier, but not so noisy, attachment screws work loose, blades smoke. Price $139.
Fein Multimaster Smoking blades, expensive blades.
All three had lots of good reviews, but Fein Multimaster had the best.

I bought the Dremel at Lowes today but after more research this afternoon I think I should return it and get a Fein. They have them at Tool Crib.
How do I know which is best for me. Of course I would prefer the cheapest, but also want one that will hold up and work well.
250 Start is $199. wonder if it has the easy change attachment feature?
150 Select is $281
250 Select $329
Top $354
Top Plus $399
At present, I just need something to cut out portions of an old maple floor that need replacing.
Thanks for anymore advice.

You want a straight 1 1/2" wide blade with finer teeth. There's one with long Japanese-saw-type teeth but that one tends to get stuck. The finer-teeth blades come in a three-pack for around $45-$50.
Casey

Casey, the Dremel I bought yesterday from Lowes cost $99 on sale and I bought seperately the 3/4" Wood & Metal Flush Cut Blade. It was in a 3 pack for $34.98.
I had never even heard of these kind of tools before you suggested the Fein. They sound like such a handy tool. There are lots of tools and reviews. I am thinking that you recommended the Fein because it is the better of them and that it will hold together and do the best job. Wondering if I dare just stick with this cheaper brand being I don't have so very much work to do with it.
Thanks for advice.