gnuber -

I've bent lots of blades on my 16.5 hp riding mower (Briggs Engine) without bending a shaft. Just putting a new blade on usually does the trick okay. The worst case was when I hit a log, and bent the tip of one blade down so it was dragging the ground, and mowed a pass clear across the yard before discovering I was being followed by a 3" deep trench with circly little squiggles in its bottom (and no grass).

Runnng the engine without the blade may be a little "iffy" depending on the engine model, since the blade may be the only "flywheel" you've got if it's a "mower special" engine, and the engine may run too rough (with no flywheel effect to smooth it out) for you to tell conclusively whether something's bent or it's just running rough.

On the other hand, 4.5 HP is pretty small, so it may not need much of a flywheel, but don't be too alarmed if it sounds a little rougher than you're used to. A small amount of vibration (the wheels stay mostly on the ground?) won't necessarily mean anything serious is bent.

Depending on the local market, you might be able to buy a replacement engine if it's really necessary, for around $70 or $80 if you're lucky, or $100 if you're not. Since you'd have to figure out how to connect all the controls, a new mower might still be "cost effective" if it meant buying any parts at all.

"Small engine repair" (i.e. lawnmower & chain saw hustling) is often a popular "home business" for local tinkerers, so you might also find a used (they'd say rebuilt) mower a little below new retail, but not many of those back porch mechanics have the budget to advertise much, so they can be hard to find unless you've shared a beer with one.

And if you don't have to hurry, yard sales where someone's bought a new one and has a pretty good old one to get rid of are a real possibility, since springtime is when people "move up" when they start thinking about cutting the grass with the old one. (Then next year you can buy their new one cheap when they've found out that the "upgrade" can't turn sharp enough to get to the edges and won't fit between the trees that mama won't let them chop down.)

Lots of possibilties.

John