Last weekend I dropped the lower unit of my 60 yamaha 2stroke to check the impeller and change the gear oil. When I went to bolt it back up one of the five bolts never got snug. I could see a discoloration on the shaft housing where the paint didn't match. I believe that bolt was froze up once upon a time and someone used a torch to heat it loose. I talked to my neighbor about it and he recomended tapping the hole and installing a helicoil. Does this sound like a good Idea. I've never used a helicoil.