sorry for your loss, crappy thing to go to your boat to find something wrong. i've lost 2 motors in the past. 25hp evinrude with bar lock across the mounts and a merc 9.9.
now, i'm not a thief but you could do all the above mods and looking at your picture. i could take that from you in 3 mins flat without a sound. you can weld all you want on or over the bolts. 3 mins and its gone. if your plugged in then like stosh says Motion sensor and flashing light or wireless app to your phone or...... put a tracer on it. there the size of a nickle and can locate your motor anywhere in the world with your phone
