2 Year Old Volvo Penta Exhaust Manifold Drain Plugs clogging with rust

GaylenP

Recruit
Joined
Jun 10, 2012
Messages
3
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?
 

MotorheadTed

Seaman
Joined
May 2, 2011
Messages
50
Re: 2 Year Old Volvo Penta Exhaust Manifold Drain Plugs clogging with rust

You must have a "half" system (block & heads) only cooling system. You could convert to a "full" system by plumbing in the exhaust manifolds, but that doesn't include the risers, they will always be salt water cooled.
I have the same siluation and I'm in the process of installing the V/P "Neutra-salt" flushing system, which supposedly neutralizes the salt in the cooling water at engine shut-down. FRom what I've read (internet search) it actually works. I snagged my (new in box) system on flea-bay for $200 shipped. You might want to check it out !
 

GaylenP

Recruit
Joined
Jun 10, 2012
Messages
3
Re: 2 Year Old Volvo Penta Exhaust Manifold Drain Plugs clogging with rust

You must have a "half" system (block & heads) only cooling system. You could convert to a "full" system by plumbing in the exhaust manifolds, but that doesn't include the risers, they will always be salt water cooled.
I have the same siluation and I'm in the process of installing the V/P "Neutra-salt" flushing system, which supposedly neutralizes the salt in the cooling water at engine shut-down. FRom what I've read (internet search) it actually works. I snagged my (new in box) system on flea-bay for $200 shipped. You might want to check it out !

Thanks for the tip. Any idea what is involved in converting to a "full" system? how do you plumb in the exhaust manifolds?
 
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