Hi,
Just had a look at your other projects after reading your post about the boat trailer guide. I noticed your problem with the power washer engine varying in speed, or "hunting". I had the same problem with a B&S 8.5 hp engine last month, and every so often the engine would stop completely. I tried just about everything possible without dismantling, but with no success. In the end a friend and I reluctantly took the carburettor apart and discovered the problem. The engine had stood for a while and had obviously been filled with bad (water contaminated) petrol. The water had caused corrosion inside the carburettor bowl and as the petrol had evaporated it had left some sediment in the tank and pipes too. Every so often a piece of crud would block the carburettor jet or cause the float to jam, which made the engine slow down. If the piece of crud came free, the engine would speed up again, otherwise it would stop. I left the dirty parts of the carburettor soaking in xylene for a while, then cleaned them up with a little brass brush. Now the engine works fine again.
Hope this helps,
Chris