rusting at manifold/riser gasket area issue?

[piratedude]

got a used salt water boat w/ low hrs on it but noticed rust at at riser/manifold gasket area flaking off...should i remove them and clean out or replace? just leave them alone? oh this is a merc 350 v8.

 

[affa]

Re: rusting at manifold/riser gasket area issue?

Hi<br />Replacing that gasket every year will increase the lifetime for manifold and risers.<br />Regards<br />Affa

 

[Eggkr8]

Re: rusting at manifold/riser gasket area issue?

I just got an old boat too and have spent every spare moment of the past few weeks taking off everything down to the block and head. What started as me replacing a leaky water pump became me discovering a large amount of scaly rust in the water passages. My repair manual suggests 'rodding' the exhaust manifold and other parts of the cooling system every 400 hours of use. Mine was a 100% fresh boat that probably never had this done.<br /><br />Procedure is to use a metal rod to knock off the large chunks of rust, then soak the cast iron parts in Muriatic acid for about 90 minutes, rinse and then use a rod again on any loose scale again.<br /><br />I was amazed at the before and after flow I got through my manifold and riser, it was a huge difference

 

[Don S]

Re: rusting at manifold/riser gasket area issue?

Procedure is to use a metal rod to knock off the large chunks of rust, then soak the cast iron parts in Muriatic acid for about 90 minutes, rinse and then use a rod again on any loose scale again.

There is a down side to that procedure. All the rust and scale buildup inside the risers and manifolds are exactly that Rust. This rust comes from the water passage, including the web between the exhaust and water. As that web gets thinner from the rust flaking off, holes finally appear and water gets into the engine.<br />Usually when a manifold flakes off enough rust to plug up the cooling passages the manifolds should be replaced. That way you are only replacing manifolds instead of engines and manifolds.<br />The other problem is you can not get to all places so you end up cleaning only the areas you can see and the rest remain plugged.

 

[Scaaty]

Re: rusting at manifold/riser gasket area issue?

Do as Don says...any exhaust manifolds used in salt should be replaced if you do not know how many hours are on them..BUT if its just surface rust, looks the same on both sides, etc, you can run them for awile until you get the feel for the boat, And run them in the water and see if either get warm..if they do (while running in the lake), replace. The will get hot after shutoff from heatsinking.

 

[Bondo]

Re: rusting at manifold/riser gasket area issue?

All the rust and scale buildup inside the risers and manifolds are exactly that Rust .

Ayuh.........<br />And, It Used to be Cast Iron.........<br /><br />Cleaning the manifold is a Band-aid, that's Alot Closer to Shooting Yourself in the Foot, than Any kind of Repair.......<br /><br />Get a New Manifold, While you Still have an Engine to Save.............