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Aluminum or Cast manifolds

E

elgineddie

Contributing Member
"Howdy team,
I am chasing the

"Howdy team,
I am chasing the illusive 'steam rising from starboard exhaust' problem. The riser is noticeably hotter. I've changed the T-stat, checked all hoses, (don't have the check-balls on my 1998 so that's a non-issue), changed lower unit H2O pump, checked the rubber flappers and checked all hoses. Everything is clean and nothing is amiss so I've come to the conclusion that it's got to be some sort of blockage in the manifold or riser.

I pulled them off and I'm shocked at the weight! Geez are they heavy! When I looked on eBay I found aluminum manifolds/riser claiming huge weight savings. But what about performance for raw water systems in freshwater? Does aluminum corrode easier than cast iron? Is warpage an issue? Just wanting to know if there are any long-term concerns with aluminum manifolds and risers.

Thanks in advance!
Eddie in Illinois"
 
"The risers were never changed

"The risers were never changed in the past 9 years. From my visual inspection I can't see anything clogging the riser or manifold passages... unless its hiding from me!

So you are voting NO for aluminum in fresh water, huh??"
 
"Risers should always be "

"Risers should always be "cool" to the touch regardless if they are in fresh water or salt water. Except at shut down when water stopns circulating thru them - they will get a little warmer. General rule of thumb is to replace your risers every 4 years (at least in the ocean). I've done it on my 4.3 L mercs, a 454 merc, and a 350 volvo - all the same once you pulled the risers and gave them a good look - totally blocked. Keep in mind too that most temperature sensors are on the block and the risers could easily be overheating without the guage showing it.

BTW, if you're looking for real skookum riser/manifolds, these will be the last ones you'll ever need (at the right price of course).

http://www.hitekmarine.com.au/"
 
"my suggestion is to go with t

"my suggestion is to go with the cast iron vs cast aluminum. Not sure there are real pronounced risks, but.... Aluminum will almost always be more suseptable to corrosion. There also the issue of differential rate of expansion that may create a long term integrity challenge to the gasket surface. Stick with what works and what was designed. cheers."
 
"I am with you Gentleman, diff

"I am with you Gentleman, different rates of expansion in aluminium can add to the challenges of maintaining a good seal and we all know how critical that seal is on the risers.
In my opinion, there is also a much greater chance of galvanic corosion internaly with aluminium risers that are bolted to big cast iron engines.
Unless you were looking to save a few Kilo's (or pounds) or you just had bags of money to burn I would stick with the cast iron.
Cheers
Peter C"
 
My turn.

I really liked t

My turn.

I really liked the one piece stainless steel real skookum riser/manifolds. Would someone send me a set for Christmas?
1987 4.3L Mercruiser BIG THANKS!!!!!!!!!
 
"Guy
Hmmmmm, nice tastes.
Ha

"Guy
Hmmmmm, nice tastes.
Have you been a good boy ??
happy.gif

Peter C."
 
"OK gents, thanks for all the

"OK gents, thanks for all the input! I think I'll stick with what's been working for years.

NOW my main issue is do I bite the bullet and spend $500 on new risers/manifolds or try to dunk them in muriatic acid for an internal cleanup? I mean these things LOOK unobstructed inside after 9 yrs and 250 hrs in freshwater but I don't know if there are other concerns such as internal pinholes and micro-cracks. Do those things even occur?

(Once one starts to worry about things, the brain can start to play tricks on you and make you spend $500 for piece-of-mind!)

Opinions here?"
 
"Eddie
If they only have bee

"Eddie
If they only have been used in fresh I would clean them do a good visual on them, get them pressue tested and wack em back on if they are OK
Cheers
Peter C"
 
Have them cleaned at a radiato

Have them cleaned at a radiator shop that uses an ultrasonic tank for cleaning. They can also pressure test them.
 
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