Boat Forum / Building / November 2005

you're dead right in your views about welding cast parts...  its
tricky, as noted by one other poster noted due to the manganese and
silicone content.  I've done a fair bit of work repairing cast  exhaust
manifolds, some with tig, but mostly with a torch.  The tig can be made
to do it, but you usually need to have at least 3-5 layers of weld to
get a satisfactory result.  exhausts are complicated a lot by the
deposits on the inside of then though, so other casts are not as
difficult.  I've had good success with lawn mowers.   If you are going
into a shop, call around and see who will do it with gas.  its true
that using the flame is harder, but in general i think you'll find that
only a few shops will have anyone who can braze at all, and those you
find will be old school old timers who know their stuff.  Just finding
someone like this is a worhtwhile experience.  You'll want to keep
their number as they will build up old parts with wear bronze, can
usually operate a lathe and mill and often undercharge for their time.
craftsment are disapearing

I have tried this myself - using a grinder to "wet-sand" aluminum plate,
using resin as a wetting agent.  Then mixed the epoxy directly on the plate,
working in well.

Held up for a few years, but eventually bond broke.  Of course, it may have
had something to do with the aluminum being used as a "skid plate" under the
bow of a plywood boat, for hard ledge landings.  The 1/8 plate was worn more
than halfway through before it de-laminated.

Good luck, and let us know how i works!

Sal's Dad