"Cruising speed"
Kim,
What do you mean by that term and where would you have read it? It is not a term that would normaly apply to a sailboat-under sail or power. Even the term "hull speed" is not very meaningful-since it is only a point at which an exponentially higher amount of power is needed to exceed, and which is fairly easy to attain with modest amounts of power. It basically explains why you might get to about 6 knots easily (1800-2000 rpms typically on most boats 32-40 feet), but might need 2700 or more RPM to get much above (assuming 6 knots is the hull speed). BTW-this is calculated as 1.34 X sq. root of LWL.
Having said all this, depending on installation, shaft aligment, and prop size and pitch, you will sometimes begin to get vibration like you describe at higher RPMs. If this occurs at a point beyond what you feel is a good speed, it is not a big problem. If it occurs below that, you should fix it. Most engines are fairly smooth up to at least 2500 RPMs. If they are high revving motors (VW, BMW, turbo Yanmars,etc.) you sould be able to get at least 3000 before much vibration..
Having said all that, for a moderate displacement 32 footer like yours with a 22 HP engine, 7 knots under power is pretty wishful thinking-certainly at "cruise power" settings (as defined in the ENGINE manual). Rarely do sailboats cruise that fast under power unless they are in the 42-58 foot range (because of the longer waterline). Frankly, for that boat 6 knots at 2K is pretty good.
Check the alignment, though!
Give us some more info about nwhere you you heard about 7 knots...
Good luck!,
S