RE: os 61 muffler question
If you check the part list in the manual, you will not see a gasket.
BTW - be careful with RTV, some of them can be corrosive to aluminum. Could eat away at your muffler and/or engine. The red RTV we have here at work is OK but that doesn't mean ALL red RTV is OK. I have seen full scale a/c parts that were eaten up by RTV in the past.