Exhaust manifolds, time to replace?

[jakwi]

So 4.5 years, mostly brackish water. Religiously used a homemade saltaway mix to rinse.

I have a new oem set, ready to go, I just thought I'd see what you guys think.
I didn't see any sign of gasket failure, so not sure what to think of the moisture inside.

this is the starboard side which is visibly worse from the outside.

 

[jakwi]

3 inch block and manifold passages on starboard side.

Honestly, aside from the moisture inside it looks really good I think

 

[jakwi]

I'm starting to wonder if I just need fresh gaskets.

 

[Chris1956]

Gee, 4.5 years is not usually a replacement point for manifolds and risers. It is usually about double that for those of us who do not flush 'em.

Get some of those silver OEM gaskets, and true up the manifold and riser sealing surfaces with sandpaper on a piece of plate glass, to give a very flat surface.

 

[jakwi]

Ok port side now

 

[jakwi]

Really I thought 5 to 7 was standard

 

[tpenfield]

Clean them up and then decide, but they look OK.

 

[Chris1956]

The terminal end of the riser usually corrodes first. Yours looks pretty good.

It looks like some leakage from the riser to manifold joints. That can be fixable, see post 4.

 

[jakwi]

This is the "bad side" starboard with the surfaces cleaned up. The elbow is a little rough, but even that is probably serviceable. I'll probably clean them up and try to sell them. They definitely have a few years left. Next time I'll disassemble and inspect before buying a new set. Probably should have done that at 3 years. Thanks for the input guys

 

[jakwi]

The terminal end of the riser usually corrodes first. Yours looks pretty good.

It looks like some leakage from the riser to manifold joints. That can be fixable, see post 4.

Yeah I wish i would have inspected before buying a new set. It is wierd how the starboard side is so much worse than the port

 

[jakwi]

Do you know what the sparkplug gap should be off hand? 357 alpha 4v sbc ngk bpr6efs

 

[jakwi]

Do you know what the sparkplug gap should be off hand? 357 alpha 4v sbc ngk bpr6efs

Seems like it's. .45

 

[Scott06]

Seems like it's. .45

Yes .45 i think only the mpi engines are .060”

 

[tank1949]

So 4.5 years, mostly brackish water. Religiously used a homemade saltaway mix to rinse.

I have a new oem set, ready to go, I just thought I'd see what you guys think.
I didn't see any sign of gasket failure, so not sure what to think of the moisture inside.

this is the starboard side which is visibly worse from the outside.


View attachment 388632

If Saltwater used and flushed with fresh water after every TRIP HERE IN NW Florida, I'd replace risers for sure. We didn't have much luck past 5 years. Now, wonder what the inside of your block looks like. Thin heads are even worse. Many Floridians have gone OBs or antifreeze cooled MCs. Is it worth hydro locking motor and then having to replace?

 

[Chris1956]

Tank, Cast iron blocks are pretty good at resisting salt water. Most people do not flush 'em, and they last 20+ years. Actually, I have never heard of a block rotting out, but I am sure they do after a real long time. I would think the cast iron thermostat housings would rot out, and the stamped steel parts don't last very long, even when painted.

The manifolds rot out after 10 or so years in salt water, if you don't flush 'em. I do not know how much you can extend their lives by flushing them, as the salt gets into the porous cast iron. A MerCruiser dealer told me that he had some used, but good cast iron thermostat housings, that he rinsed off and stored in the attic. They continued to rust, even in that dry environment.

 

[jakwi]

Yeah i figured better safe than sorry, besides I'd already bought the new parts. I am going to clean up the old ones and try to sell them, they might give someone a few years of use. Beside I can afford the manifolds, but not a new engine.

While I was reassembling I noticed my coolant lines felt crunchy, which I thought was wierd. I looked inside and it looks like there is a restriction building, kind of like a clogged artery. Should these be on a routine replacement list? Engine has been in service for 16years.

 

[jakwi]

This is the line that feeds the starboard side. This side gets noticeably hotter than the port side, but I can still keep my hand on it while running. Port side is cool to the touch.

 

[Chris1956]

Heater hose is pretty cheap. I would replace them.

 

[Lou C]

Agreed I’d definitely replace that hose. I have heard the same thing about blocks not rusting out here from 2 different marine mechanics here in LI when I asked about closed cooling for a new or reman engine. However the heads can rust thru this I have heard of. When I replaced mine due to overheat damage at 2017 they had been used in salt water for 15+ years. The cooling passage in them were definitely getting eroded who knows how thin the cast iron was behind the valve seats.
Manifolds I have replaced every 5-7 but that was when I had the one piece OMC V6 units. The last set I put on a few years ago I had to convert to the later style just like OMC & Volvo used. With these at 5 years I will inspect if the manifolds look good I may continue to use them (if the sealing surface cleans up 100% & they pass the acetone test). The elbows for sure I’ll probably replace. I guess all salt water isn’t the same. If I got a new or reman engine though I would add closed cooling at least a half system.

 

[tank1949]

Tank, Cast iron blocks are pretty good at resisting salt water. Most people do not flush 'em, and they last 20+ years. Actually, I have never heard of a block rotting out, but I am sure they do after a real long time. I would think the cast iron thermostat housings would rot out, and the stamped steel parts don't last very long, even when painted.

The manifolds rot out after 10 or so years in salt water, if you don't flush 'em. I do not know how much you can extend their lives by flushing them, as the salt gets into the porous cast iron. A MerCruiser dealer told me that he had some used, but good cast iron thermostat housings, that he rinsed off and stored in the attic. They continued to rust, even in that dry environment.

It must be our hot weather added to the salt that causes our iron products to rot through sooner than most. We seldom winterize in NW Florida. It is always HOT or warm! We might get 5 years out of salt water cooled risers, with good flushing. Manifolds seem to last a couple of years longer. I had a 1986, 8-year-old CHEVY V8 MC head rust/rot ( back 1994) through the thinnest part of the iron. Inside of block's cooling cavity didn't look worth rebuilding. Of course, motor had hydro locked and even burnt up starter because I didn't realize motor had hydro-ed and kept foolishly cranking. Inside of blocks cooling cavity didn't look worth rebuilding. Passages were closing. Perhaps newer V8s have better metals, but I've even had a Mercury OB's head rot out. I'd just bite the bullet and replace riser ever 5 years and I slept well. Imagine a $30K Yamaha rotting out??? You can still find rebuildable Chevy blocks and heads. I have an extra core in my garage. I learned really quick, after spending a grand at a marina, that MCs are cheaper to work on at HOME than paying for a mechanic.