Originally Posted by
smittythewelder
If you feel like getting rid of the scaly carbon, have your local auto machinist leave the pipes in his hot-tank over the weekend, assuming he has the hot caustic soda.
That "scaley" looking stuff is some sort of expanded metal used to hold the muffling material in place . This is an "internally" silenced pipe. The only one I have ever seen.
I haven't been around this game in far too long; is there really a lower unit nowdays that will stand up to those big twins?!
I use stock 302 Yamato lower units with a LeeTietze nose cone . The only problems I've had were "self-induced".Bad line up and or tower flex. There is a pic of the "flexi-flyer" in the thread . It was the first one I made for a Polaris. With the F/C 340 , it was OK cause it only 35 or so HP but the L/C
ate couplers and input shafts. These "wide-footed" towers take care of that.
I have never had one of these go south internally in 5 years.The 3/16" shear pins are just barely enough.
The other thing that I'm wondering about from your pix is whether that towerhousing might twist significantly under full power. I think that's why a lot of towerhousings were made using a piece of chrome-moly tube in the middle. Bill Rankin once told me about watching a dyno run of a Mk75 at the Mercury factory, and that they measured an amazing amount of twist from bottom to top of the block.
Pretty work!!
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