In 2009 after 18 years I finally had to replace the exhaust manifolds on my 1991 Volvo 570A/PS with 290 DP with fresh water cooling that runs exclusively in salt water. (Not bad!) The boat comes out of the water at the end of the 3 month salmon fishing season and as part of the winterization process I drain the exhaust manifolds and disconnect & drain the raw water hoses.
This year when I was putting the plugs back in the ends of the exhaust manifolds I was alarmed when I noticed a fair amount of rust partially clogging up the drain holes that must've washed out while it was draining at the end of last season. I poked around with a small screwdriver and scooped out more rust flakes - about a half hand full from each manifold.
I know that hot salt water + cast iron = rust, but how much is 'normal'? How long should I expect these new(ish) exhaust manifolds to last? And is there any practical way to extend the life of the manifolds during the fishing season?
This year when I was putting the plugs back in the ends of the exhaust manifolds I was alarmed when I noticed a fair amount of rust partially clogging up the drain holes that must've washed out while it was draining at the end of last season. I poked around with a small screwdriver and scooped out more rust flakes - about a half hand full from each manifold.
I know that hot salt water + cast iron = rust, but how much is 'normal'? How long should I expect these new(ish) exhaust manifolds to last? And is there any practical way to extend the life of the manifolds during the fishing season?