How Soft is an Aluminum Motor?

One of the downsides to an aluminum block is the motor is fairly soft and it caution is not exercised you can easily strip bolts in the motor. Over the years this has manifested its self on our Flying Scott on the two top starter mounting bolts.

For our motor, the starter has always been an issue and I'm not sure if the bolts were stripped before I got the motor or if they were stripped by Action boat when they "worked" on the starter or if I stripped them in one of my many R&Rs of the starter.

The solution to this problem was to install a set of Time-Serts. These hardened steel sleeves are an ideal fix and actually result in a higher pull resistance than the original aluminum block. The Time-Serts for this job are the 5/16-18. This allows you to use the original size starter bolts. They are sold in a kit with 5 Serts, the drill, tap, counter bore and installation bit.

Installation was very easy, if fact a little too easy. The aluminum is so soft the drill cleaned out the old threads in seconds and the tap, which is usually the hard part, was easily turned with a tap wrench after lubricating the hole with WD-40. The tap turned into the hole with little resistance and cut beautiful new threads. The counter bore created a nice indent for the Sert and the final step was to screw in the Sert with the supplied driver tool. In under 10 minutes the motor was ready have the starter remounted.

My observation is that the Aluminum is really soft so I need to take extreme care in not over tightening any of the bolts/screws in the block. The good news is the Sert completely eliminates the need for the starter bolt to come in contact with the aluminum on future R&Rs. Now I have a nice strong attachment point for the starter.