A common issue with the older speed boats from the 70's and 80's is that the alloy exhaust heat exchanger manifolds, commonly called marine manifiolds, are quite often rusted through and very thin.  This effectively leaks water too close to the exhaust ports and there is a danger of too much water entering the exaust valve and into the cylinder, which can terminate engine parts.  Here I have fitted our new AussieSpeed marine manifolds to a 308 Holden V8 whihc is sitting in a Flycraft clika ski boat.  I was able to rewok the stainless steel pipes to suit.  I can make new pipes too if need be.