Exhaust Manifolds: Should I replace them proactively

[1980Coronado]

Last night I winterized my 1980 Coronado and when I drained the goose neck/riser on the starboard side, quite a bit of metal flakes ran out. I've winterized I/O's before, and have seen stuff come out before, but not in this quantity. I used a wire to poke in the hole as the water came out and was surprised by the amount of junk that came out. Didn't get much of anything out of the port side except the water. This is only my second season with this boat and all indications are that these are original manifolds and risers. Last year when I winterized, I had to drill out the 1/8" NPT holes and go to 1/4" plugs because the threads were so rusted/rotted out that the 1/8" plugs wouldn't thread in anymore. I drilled both manifolds, but could only do the starboard riser. The port riser is the same part as the starboard and I couldn't get enough clearance from the motor to drill that riser....and it really needs to be drilled and tapped for the 1/4" plug. I either need a right angle drill or I'm going to have to remove it to drill and tap. After I drained the port riser I could just push the 1/8" plug back in the hole even with Teflon tape on it to try to get it to thread in.

I have no indications that there is a cooling problem or that the manifolds or risers are bad in any way at all....but the age of them and the amount of junk that came out of the one side makes me wonder if I should just replace them.

Engine: Mercruiser (454 cid) Model MIE 330 S/N 5652430 (straight inboard)

Exhaust manifolds are no longer available: Port 47735A 1, STBD 47736A 1


My wallet tells me not to fix that which isn't broke....but?

My question is should I be proactive and replace the manifolds and risers? If the answer to that question is yes, where do I get them since they are no longer available?

 

[HT32BSX115]

Re: Exhaust Manifolds: Should I replace them proactively

Howdy,


If you have 30+ year old risers and manifolds, I would say you got a FULL life out of them!!!

I would pull BOTH risers and manifolds and closely inspect the sealing surfaces. If there's ANY question, I would replace them with what ever will fit.

If you wait until they start leaking, you'll be just like "you were attached to another object by an inclined plane, wrapped helically around an axis" ..................Or possibly your engine will be......

Looks like BARR still makes them and Marinengine.com sells them You might even be able to get them right here on iboats!




http://www.marineengine.com/newparts/part_details.php?pnum=BARMC-1-47736&ptype=&Engine=&Model=


If it were me, depending on how much room there is back there,if they're bad, I would go to center riser type manifolds and risers, and re-plumb the entire exhaust system with new thru-hulls, and maybe add mufflers etc.....

regards,


Rick

 

[1980Coronado]

Re: Exhaust Manifolds: Should I replace them proactively

That's not what I wanted to hear Rick!

Need someone to suggest replacements....My risers come off the back of the manifolds...do they make a kit to convert the old 454's to a center riser? I found GLM but can't find a kit for my motor.

I have room (within reason) because it's an inboard....not an I/O.....no Y pipe, exhaust hoses go straight out the back....no need for mufflers.

 

[HT32BSX115]

Re: Exhaust Manifolds: Should I replace them proactively

Yeah.......Even the BARR manifolds look expensive!

I am not all that familiar with the older 454 heads but it looks like any 454 manifold would "fit".

You would only need to match up the thru-hulls with the newer risers then using regular old 4" flexible exhaust pipe. It would of course, depend on how much room you have in the back, above and behind the engine.

I have 3" riser extensions on mine and you can see where my thru hull (hole) is in the picture below. (It's to the right of the vertical red wire, upper right corner of the picture.........I am not using them either....I went to thru-prop exhaust when I installed the engine!! The previously installed OMG 460 had a Corsa Capts Call system that I didn't put back in)



Also notice that the top of the riser is quite a bit higher than the flame arrestor too. (although it's hard to see from this angle)

But if you have a V-drive you probably have more room behind your engine and if you have enough room above your engine you might be able to use regular center riser manifolds (with or without extensions) and just use rubber hose to hook to the thru-hulls.

If you do not have enough room above, you may have to raise/rebuild the engine cover to accommodate the taller risers.

 

[1980Coronado]

Re: Exhaust Manifolds: Should I replace them proactively

Rick,

Since it's a straight inboard, the engine is in the center of the boat and the exhaust hoses run next to the stringers from the transom then make a 90 bend straight up into the exhaust riser. I don't believe I currently have any spacers and don't think I would need them. I need to check to see if anything is attached to the manifolds in the front, like the alternator, fuel water separator etc...I believe there is enough room under the engine cover to accommodate this type manifold without spacers, but what other mods will I have to make is the question.

It looks like converting to the center raiser manifolds would actually be less money than replacing what I have by quite a bit, if they have a kit that will fit.

 

[HT32BSX115]

Re: Exhaust Manifolds: Should I replace them proactively

Rick,

Since it's a straight inboard, the engine is in the center of the boat and the exhaust hoses run next to the stringers from the transom then make a 90 bend straight up into the exhaust riser. I don't believe I currently have any spacers and don't think I would need them. I need to check to see if anything is attached to the manifolds in the front, like the alternator, fuel water separator etc...I believe there is enough room under the engine cover to accommodate this type manifold without spacers, but what other mods will I have to make is the question.

It looks like converting to the center raiser manifolds would actually be less money than replacing what I have by quite a bit, if they have a kit that will fit.

That will be because your transmission moves the engine forward quite a ways. I think that would make it FAR easier to make the change!

I would be surprised if you have any accessories bolted to the manifolds. Filters and such would be easy to relocate.

The alternator would be a problem but you could probably use a different mount.

You can probably buy a complete manifold/riser kit for almost as much as one of those original manifolds!!


You'll just have to do a little replumbing of those exhaust hoses. I would completely replace them but they're pretty pricy (per ft) too.


You can easily buy stainless steel 4" tubing to make splices if the original tubes are in good shape.

That way you could piece together a hookup. you can even buy 45 and 90 degree elbows to make whatever you need to make it all hook together.





Are your exhaust outlets always above the water-line?

 

[Don S]

Re: Exhaust Manifolds: Should I replace them proactively

Why don't you just pull the exhaust elbows off and inspect the gasket surfaces of the manifold and elbow. Being in fresh water, they are probably fine.

 

[1980Coronado]

Why don't you just pull the exhaust elbows off and inspect the gasket surfaces of the manifold and elbow. Being in fresh water, they are probably fine.

I have to pull the starboard one anyway to drill it for a 1/4" plug....might as well pull both. I just hear all the horror stories about engine damage due to rotted out manifolds....I've had no issues....just being a worry wart.

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[Don S]

Re: Exhaust Manifolds: Should I replace them proactively

I just hear all the horror stories about engine damage due to rotted out manifolds

It's fine to be concerned, but inspect first, just don't start looking for parts and think new parts are needed.

 

[1980Coronado]

It's fine to be concerned, but inspect first, just don't start looking for parts and think new parts are needed.

Thanks Don.....will do.

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