Lawnboi - hi, I think Murray made the Sentinel line...here's two places you can try out (I posted this info in the Test area for someone else):

Jack's Small Engines - 1-877-73-PARTS - I've used them before for parts (not manuals) and had excellent service from them; they're in northern Maryland and open 8 - 5 EDT.

Outdoor Distributors - 1-877-70-PARTS - I've used them before for parts and had excellent service from them. They're in Alabama and they're open 8 - 5 CDT.

I also used Google to search for "sentinel lawn mower" and got a few hits...a couple of them referred me right back to Jack's and Outdoor Distributors. I don't know how old your lawn mower is - you could always call Murray's nationwide customer service network at 1-800-251-8007 (obtained from their website) and see what help they can offer. You'll definitely need the full model number for your lawn mower when calling any of these places. Hopefully, you can locate that number...typical places include under the seat, on the rear frame behind the seat area, and under the engine hood. Good luck! Jim D/West Point, VA