25hp Four Stroke Lower Unit Help

I was wondering if any of you guys have had any problems with the bolt holes that connect the lower unit stripping out. I have three of the four bolt holes stripped out!!! Has anyone had this problem before and if so what are the fixes? I have read about using a helicoil but I am not sure of the size I would need. I cant find anything on the bolt and thread size either. I have a 25hp Four stroke fuel injected. (nsf25B) Any help would be appreiciated.

If the bolts were over-tightened, or if an isolation material (such as loc-tite or aluminum-based anti-seize compound) was not used, galvanic corrosion and galling could cause the threads to bind, and during removal, the softer aluminum would fail first. Likewise, if the water pump hasn't been serviced since new, the bolts have been in there a long time. That may be your issue. Proper torque is important, and so is galvanic isolation.

Yes, a stainless insert is called for. That could be any brand -- helicoil or time-sert, etc. The bolts are, I believe, (don't have one here at the moment) 8 or 10 mm. The head size is a clue... a 12mm head is usually for an 8 mm bolt... 13mm heads are typically used on 10 mm bolts. If you give Tohatsu America a call at 214-420-6440, they can help you with bolt specs.