On Thu, 30 Mar 2006 21:51:07 GMT, – Colonel – wrote:

I need to pull, inspect and probably replace the exhaust manifolds and
risers in my six-year-old, raw-water-cooled inboard 350.

I want to minimize the hassle and expense of having to replace the
cast-iron manifolds and risers every 6 years, but I'm not sure which
way to go. Help!

Here's the situation:

1. The marinizer of my engine (Pleasurecraft Marine) doesn't offer a
full freshwater-cooling system for my motor (GM 350), and I don't want
to get into a lot of reverse-engineering at this point, so freshwater
cooling is off the table.

2. I can get a set of cast iron manifolds and risers for about $600 but
then I'm right back in the "change them every six years" merry-go-round.

3. I've been considering using aluminum exhaust manifolds with zinc
anodes, but everyone I talk to says don't do it. It seems to me that
outboard motors are made of aluminum and THEY don't rot out like cast
iron (so long as they have active zinc anodes) so what's the problem?
My engine runs cool – normal operating temp is 140° F – so it's not
like I'm going to have salt "baking onto" the insides of the manifolds,
and anyway, I flush the motor with freshwater after every use. (Boat
lives on a trailer.)

What do you folks think? Are the aluminum manifolds and risers (about
$100 more than the iron ones) worth a try? Has anyone here ever used
aluminum manifolds and risers on a raw-water-cooled inboard?

Should I just stick with the crap-iron stuff and get used to the idea
of replacing them every 6 years?

Thanks for any information or advice.

Col.

I'd thought about stainless or aluminum manifolds and risers when I
replaced mine (eight seasons old, Chesapeake Bay). Like your experience,
everyone I talked to said it wasn't worth it. I put the cast iron ones back
on again. I'll replace them in seven years, whether they need it or not. At
$100 per year, it's one of the cheaper aspects of boat ownership.
--
'Til next time,

John H

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