TSP, trisodium phosphate, is a very common, inexpensive, and very effective, non-sudsing cleaning agent. It is highly basic (alkaline), useful for removing some kind of stains and works well as a degreaser. It’s use has declined in recent years because of concern about phosphates causing eutrophication of waterways, but it’s a very effective cleaner. There is something called phosphate free TSP (and our name!). It contains sodium sesquicarbonate, similar to baking soda, and works similar to TSP. I’ve used it and it seems to work reasonably well.
TSP is used by painters because it is a good cleaner and paint de-glosser, so it might be best to keep it off of your canoe’s paint. It might also de-gloss the varnish a bit.