Rust at exhaust port

"2 months ago, I noticed rust

"2 months ago, I noticed rust and rust flaking at the starboard head, center exhaust ports on my '83 Mercruiser 260 (GM305). Where might the water have come from?

To assure a good seal, I installed 2 Quicksilver exhaust gaskets(not paper), new manafold, new riser. There is slight discoloration at the site as it took a couple of times of torquing down the manafold and firing the engine up. I plan to paint the site and watch for discoloration, peeling etc. After 20 hours of cruising, so far so good, but need to do the paint thing to confirm problem solved. Not convinced yet.

Any recommendations, seen this before??

Great site!! Thank you, Roy

exhaust port before"">exhaust port after JB weld and flush file

"Roy, You really need to find

"Roy, You really need to find the leaking water source. I will guess you boat in salt water.
The exhaust manifold should not allow any water to touch the block, and you would see this. It may be leaking from the riser to rubber boot to exhaust elbow connections. These should be double clamped, but they still leak sometimes. These are significantly higher than the engine block so water could possibly run down to the block. It could also be leaking from the manifold to riset joint, although a leak in this area usually allows water into the exhaust manifold gas area, and subsequently into the engine itself."

"Hi Chris,

Good observation

"Hi Chris,

Good observation! I'm thinking the possibility you mention involves the gasket between the riser and manifold slow leaked and water ran down the Manifold to the aformentioned area. I didn't have the eyes/experience to see it and water damage was cumulitive.
FYI:
The exhaust hoses run to below the level of the riser and exits, so leaks there would'nt impact the area in question. Hoses are double clamped (S.O.P.)

I've replaced the manifold and riser. Hopefully the JB WEld build up/flush filing (as shown in the photo)} and extra exhaust gasket idea will hold up. I'll keep an eye on it. If your right, replaceing these components will have solved the problem. Thanks!"

"I hate to say it, but Mercrui

"I hate to say it, but Mercruiser exhaust manifolds tend to have this problem (due to skimpy gasket clamping surfaces. You'll have to check that your manifold(s) are not warped at the gasket surfaces, which would cause this. Don't let it go! Water coming there can wreck your engine.

Jeff"

"Hi Jeff,
Thank you for the

"Hi Jeff,
Thank you for the word to keep an eye on those manifolds/riser gasketing surfaces! Hopefully, aftermarket product is better. I installed Etco replacment manifolds and risers with the raw water S.S. restrictor plate (not blocked, just restricted in two flow-through channels so temp. conduction is better[?]). They ARE quieter (more iron volume?). I'm ordering a replacment set. Is Erco good or can you recommend an alternite product? Perhaps the} gasketing design for all manifold/riser manufatcuters is a problem? Pity though... Roy"

"Chris,

I've been think

"Chris,

I've been thinking about your observation about the leak coming from the hose off the riser. I realized you are right in that a leak could get to the head ports from a leak there! The joint is above the level of the exhaust port and gravity can do the rest. Again, Thanks! Roy"

"Right. THe water ALWAYS goes

"Right. THe water ALWAYS goes to a point higher than the exhaust ports. Aleak anywhere in the system will, therefore, run down into the ports and...Yikes!

Jeff"