Using timesert for thread repair in cast aluminum

[KiwiKen]

Hi,


I need to use a timesert to repair the threads for the lower unit oil plug on my 20HP 2008 Mercury outboard. According to Mercury Customer Support this plug is made of zinc plated steel and the lower unit is cast aluminum. The timesert kits come in zinc phosphate plated carbon steel or stainless steel. My first thought was to go stainless but then I was wondering if this is a bad idea from a galvanic corrosion perspective. I am not sure this is even an issue for this usage since the timesert should not even contact the salt water.

Can anyone offer advice on which would be the best option? Zinc phosphate plated carbon steel or Stainless steel?


Thank you,
Ken.

 

[CharlieB]

Re: Using timesert for thread repair in cast aluminum

As long as the repair still seals under the washer it should work.

Check oil regularly just to be sure it hasn't leaked.

A heli-coil can be cut short to fit the short thread necessary for your repair, the insert could be saved for a later repair as it is much larger in diameter than the heli-coil.

Worst case repair, have a local machine/welding shop weld it in, drill, tap new threads, still cheaper than replacing the casing.

 

[polar]

Re: Using timesert for thread repair in cast aluminum

I did that repair to my Merc 115 about a year ago. I did not use the stainless and the repair worked great. No leakage and it seems solid as a rock.

 

[KiwiKen]

Re: Using timesert for thread repair in cast aluminum

Thanks for the advice. I will have the parts in a few days... hopefully it will also go well for me.


Ken.

 

[KiwiKen]

Re: Using timesert for thread repair in cast aluminum

Hi All,


Finally getting around to following up regarding my thread repair. I decided to go with a regular carbon steel timesert to fix the thread and am very happy with the results. I purchased the timesert kit with a few inserts of varying lengths, a tap guide (helps to make sure the thread tap goes in exactly straight) and some loctite. The instructions that come with the timesert kit are pretty straight forward but still I took my time (checked everything multiple times etc) since it was my first time using timesert or any thread repair for that matter.

The tap guide is basically a piece of machined steel rod with the outside knurled and with a hole down the middle sized to take the tap with minimal clearance. The idea is to hold the tap guide securely against the hole being tapped so that the tap starts off straight. I have to say that the tap guide is quite expensive for what it is but for this application I think it was well worth the expense since the oil plug needs to be straight to make sure the seal is good.

I also followed advice I found in other forum posts? namely I loaded the tap with grease before cutting the threads to trap aluminum shavings etc and I also cleaned the threads afterwards with cotton swabs which seem to do a good job of snagging any remaining aluminum shavings. I also ran the old gear lube through a couple of times straining it each time to remove aluminum shavings. This all seemed to work well for me. The new thread seems really solid and no issues when changing the gear lube at the end of the season (no water in the gear lube and absolutely no sign of aluminum filings etc). Thanks to all who offered advice on the issue. Much appreciated.


Ken.