Mercruiser 5.7 Exhaust Manifolds

[peterberthel]

Both genuine and after market exhaust manifolds appear to have a maximum life cycle of 5 years with salt water cooling. One option is to purchase stainless steel "extractor' type manifolds that also incorporate the risers and extensions. The sales promo appears really favourable and many testamonials provided by the manufacturer are also very supportive. Some of the best critiques come from competitors and from users that with not so favourable experiences.

Anyone with any comments?

A second option that may be considered is to insert sacrificail anodes into the screwed plugs in the manifolds, extensions and risers in order to inhibit corrosion to some degree. Anyone attempted this?

Peter

[SG67]

My brothers 485 merc manifolds were completely eaten away,got a price for stainless and was told that they dont make them for that model(queensland based)so got genuine from the states,but i was told that the stainless manifolds are only welded on the outside & not on the inside,so their is a chance of leaks.

[Snapper_Kev]

I have a Stainless Manifold / Extractor on my 470. This model in particular (from the Qld. Manufacture) are prone to internal cracking as mine did.

I have had to have it completely dismantled (cut open) and re-designed and re-welded to fix it.

Great concept, but in the case of the 470’s anyway, poorly designed. Going from a cast head to stainless manifold and being made of different metals they will expand & contract at different rates! Hence the cracking….

Haven’t heard anything (good or bad) about the 5.7ltr variety.