Rusty droplets inside manifolds/spacers

[Sicktght311]

Posted this on the Sea Ray group, and the responses have been mixed. So posting here to see what the forums think

My Sierra manifolds/risers/6" spacers are all 4 years old. Wet joint setup on a 7.4L MPI in salt water in the northeast. In the slip from April to October, then on dry land all winter. No fresh water flushing while it's in the water all season

Anywho, as part of spring maintenance, I pulled the risers to inspect the passages, and while all the water jackets looked fantastic, the inside of the exhaust ports were filled with droplets of rusty condensation.

My thought is just cold winter, plus warming spring air, means condensation, and once the motor starts up and runs for this first time the season, all of this quickly soots up and burns off.

But it's enough that it's making me second guess, and I'm here for everyone's opinion.

Risers themselves look decent as well too. No major corrosion except for the small water jacket hole at the bottom of the starboard riser has some corrosion/plugging up. The other side is fully open.

Thoughts? Pics attached. 2 pics are looking down the spacers exhaust ports into the manifolds. Other 2 are the mating surfaces and water jackets, and then one pic of one of the risers. The other looks the same

 

[douglee25]

Looks pretty normal to me

 

[scrumper]

If I'm not mistaken, pic 1 (img_7006) shows a little shiny pool of water in the exhaust manifold?

This is probably down to exhaust reversion, the cam overlap allows for the exhaust and intake valves to be open simultaneously for part of the cycle and that causes the exhaust to be drawn back into the manifold. Under the 'right' conditions, that also sucks back some of the raw cooling water.

I agree the risers look good but I'd still plan on changing those out fairly soon, no? 4 years is starting to get up there. And why not now, you have it all apart, you're already on the hook for new gaskets as it is... It's a lot easier than rebuilding the engine (ask me how I know) and then you can rest easy for the next few years.

 

[Scott215]

Scrumper got a good point

 

[bfernald0]

Had the same thing on my 7.4 mpi. See pics below. Test your oil for sodium and do a compression check. Betting you have lower compression toward the stern as water runs downhill. Manifolds are shot and they're aftermarket to boot. The ones in the pictures were also aftermarket. Porous Chinese steel.

The max for oem manifolds/risers in saltwater is 5 years. Wouldn't trust aftermarket more than 3.

New manifolds, risers, oil test and compression check are in order.

Additionally, I ended up replacing with 496 manifolds and stainless risers with the dry joint. Bolt holes on the block match right up and it worked great. If you plan to keep the boat, might be worth it. Regardless, stick with oem on the manifolds/risers. Would not trust any aftermarket on manifolds/risers in saltwater.

Brandon shared 17 photos with you

www.amazon.com

 

[bfernald0]

Would check the plugs for signs of corrosion as well.

The exhaust passages should be soot black, no corrosion whatsoever. The fact that youve got corrosion in there, means you have excessive moisture, which means the exhaust valves are corroding as well, which ultimately is what gets you.

Corrosion leads to loss of compression, and ultimately a stuck valve, which leads to a blown engine. That or hydrolock.