We need more information. What brand boat, what year, what model/size, is it a mod v hull or deep v hull? There should be a coast guard rating plate on the boat, do you see one? My 1652 mod v is rated for 50 hp with a console and 35 hp with tiller.
I'm not sure what the 91135 refers to (it might be the serial number) but the V model is a small jet pump for the 18 and 25 hp Mercury motors according to Outboardjets.com
Here's a link to the instructions for the V model.
http://outboardjets.com/download/jet_kit_instructions/V.pdf