I'm trying to remove the top cover of my upper unit to check bearing and replace seals (1973 #1 mercrusier). Has a special star shaped bolt head. No socket I have will fit. Grabbed it will my trusty vice grips but still would not loosen (as soon as I saw they were going to slip I stopped since I did not want to ruin the head of the bolt). I also read that sometimes these break off ruining the case. Does this require a special socket? If so are these commonly available because this is the first time I have seen this type? Any tricks on getting these out because they seem really tight. Don't want to ruin my upper drive. <br /><br />By the way, I have the upper and lower separated and oil seepage out my lower unit's seep hole seems to be a leak around the shift shaft. Thanks for the hitting the nail on the head! 
I'm going to reseal the entire lower unit and the upper unit if I can get the top off.
I'm going to reseal the entire lower unit and the upper unit if I can get the top off.