I know this subject has been beat to death in the past but I'm looking for the best engine/pump combo for my 50 gallon skid. I'm mainly applying pre and post (Triplet and Prodiamine) with Surf King surfactant. I used to own a Lesco Space Saver with a 5.5 Kaw/D403 but with what I'm doing now that's overkill. I've looked at some generic 5.5 hp engines on ebay (Carroll Stream) for $159.99. I'm thinking about a solid 3/4 x 5/8 shaft adapter with 4 set screws to couple this to a a 4101 roller pump mounted on a base plate. I'm kind of stumped on the max 2600 rpm rating on the pump though. This engine is 3600 rpm. Any ideas? Am I going to be forced to go with a belt/pulley drive system, or can I get a smaller hp engine and couple directly to the pump? I would like to stick with the 5.5 hp so that in the future I can go up to a hypro diaphram pump with gear reduction, etc. Advice please.