1. Briggs & Stratton website: Visit the Briggs & Stratton website and search for your specific engine model. You can usually find the model number on a sticker or plate attached to the engine. Once you find the correct engine page, you can access and download the Owner's Manual in PDF format.
2. ManualsLib website: ManualsLib is a website that hosts various user manuals and guides. You can find the Briggs & Stratton 15.5 hp mower engine manual by searching for the engine model number. The manuals on ManualsLib are available for free download.
3. Amazon.com: Amazon also sells digital versions of Briggs & Stratton engine manuals. You can find the manual by searching for the engine model number and selecting the digital manual option.
4. eBay.com: Similarly to Amazon, you can find digital copies of Briggs & Stratton engine manuals on eBay. Search for the engine model number and make sure to select the digital manual option when purchasing.