Ok,
On level 1 (burning pellets) with a feed of +4 and air of +1
At the top of the exhaust cover box on the cover itself I got a reading of 180 degrees.
In the middle of the box it was 160 degrees.
At the bottom of the round tube that goes into the exhaust box the reading was 245 degrees.

On level 2 - top 210, middle 170, top of tube 260 degrees.

It looks encouraging; i think you would be able to capture plenty of heat with a heat exchanger plate attached to the cover.
you may want to make a different cover thats a little heavier. but that shouldn't be that big of a deal.

Just for giggles i also checked right behind the burn chamber just below the fan
it was well over 280 degrees.

this little stove burns dam hot!

i'm going to use a infrared thermometer on the outside of the exhaust cover and see what it reads at level 1.
typical boiler temp is between 120 and 180 degrees if i could get something in between without having to take it up to a level that's too high it might be worth it.

there again if the water was circulating often enough how hot would it really have to be?

ideally you would like it to be as close to the flame as possible, but is it necessary?
what you would need to know is the temp. of the boiler system you are running, and compare it to the temp at the exhaust cover on level one and see what the difference is and increasing the levels untill you match that temp. of the boiler if possible.
i'm not sure why there wouldn't be enough room ? the cover is right next to the panel on the right hand side of the 115.
could you put the cover back on as "is" - no, it would need to be modified.

i think so far the way to go would be to replace the exhaust fan cleanout cover
with a modified cover that has a plate heat exchanger attached to it.

you would also have to alter your side panel (if you wanted it closed) a little but thats the least of your worries at this point.

Has anyone came up with a idea on adapting a 115 to a boiler already in use?

well it looks like i will pass on trying to use pellets as my main fuel.
with the price of corn the way it is i'm going to have to burn pellets.

maize

Ok guys its been a while since we had a post about anyone burning cherry pits.
who's doing it? what are your settings? and how do you like it?
i have a local supplier that wants $210.00 a ton and i know nothing about them.

thanks for the help,

maize