The lower unit on my 2002 15hp Mercury
two stroke has seen better days. It's not dead yet, but I need some help with it.
Because of a stripped screw and mangled screw hole a couple of years back, I had to glue (with Marine-tex) a small aluminum
plate over the oil
vent hole and tap a new screw hole in that. It worked fine for a couple of years, but when I had the water
pump replaced last month, the guys at the shop apparently over-tightened it because the threads stripped out and it leaked. I solved
this problem by re-tapping the threads in the aluminum
plate one size larger and getting the appropriate bolt for it. I wrapped the screw threads in teflon tape, put red RTV gasket
maker under the bolt head
and tightened it down. Then I put more gasket
maker over the top of the bolt head
just in case.
This looked and felt completely leak-proof, and for about a month it worked great. Then I noticed that the hole was starting to ooze gear oil
again, this time just a tiny tiny bit. I was able to tighten the bolt another half turn, and now the leak has stopped again. Maybe the vibrations had loosened it up a bit or the gasket maker shrunk when it hardened.
Obviously I need to drain, inspect and replace the oil. But how can I avoid going through this process yet again? I am hesitant to tighten the bolt too much, lest I break the threads in the aluminum plate, but if I don't tighten it enough it will leak for sure. Is the teflon tape helping or should I use something else? Is there a better sealant
to use? Thread locker perhaps? If so, which one? (please be specific)
Any advice is appreciated.