Mercruiser 140 Manifold Riser Extension?

[nrasnake]

Below is a picture of my exhaust manifold on my 1985(?) 3.0L (SN 6891354). Is the piece on top with the bolts sticking out of it a spacer? Is this original? If not, what would be it's purpose?

I cracked into all this today and based on the amount of rust in this "spacer", the riser (elbow - not shown), and the end of the manifold... I'm planning on replacing everything, but I'm not finding the spacer (that looks like the one I have now) anywhere. Can anyone shed some light on this for me please?

For laughs, any reason I shouldn't replace everything? Is the severity of the rust suggesting a definite replacement? I bought the boat two winters ago and was told it sat for 3-4 years. I did have it running last summer before I started my transom overhaul. It seemed to run fine, but did eventually started to creep up on 180 degrees or so after about 10 minutes and I shut it off. I assumed at the time it likely needed a thermostat and that was the cause of getting hot. I did just replaced the thermostat and there was some significant rust in the housing. It seems now my problems could be worse.

One of the ports in the "spacer":

Manifold end with plate removed:

Thanks!

 

[Bt Doctur]

Re: Mercruiser 140 Manifold Riser Extension?

original, allows the riser to match with the exaust pipe

 

[nrasnake]

Re: Mercruiser 140 Manifold Riser Extension?

Thanks Bt Doctur.
So does anybody know where you can find this part?
I'm not seeing it in the BOM here
Mercruiser GM 4 Cylinder (120, 140, 2.5L, 3.0L) Sterndrive Exhaust Manifold Exploded View - iboats

Should I be replacing everything?
Thanks

 

[nrasnake]

Re: Mercruiser 140 Manifold Riser Extension?

So I think I found what I need. It appears what I was calling the "extension" (the short twisted spacer piece between the manifold and the exhaust elbow) is no longer available. This is the direct replacement which is the "extension" and elbow all in one piece:

SIERRA 18-1975-1
REPLACES OEM # 12076A2
FITS LATE MODEL 4 CYLINDER 3.0L/LX AND WILL DIRECTLY REPLACE THE 2.5L 140 HP MANIFOLD
(#18-1973 ABOVE) PLUS THE ANGLED ADAPTER
IT WAS USED WITH IF THE ADAPTER
IS NO GOOD (IT'S NO LONGER MADE)

Is this correct? Any issues with fitment or alignment? Does $126 sound about right?

Thanks

 

[Chef Shawn]

Re: Mercruiser 140 Manifold Riser Extension?

I actually have one off an engine I no longer need. The exhaust manifold and riser (what you need) are in pretty good shape. PM and we can talk. Not looking to get rich, just looking to get a fellow boater back on the water.

 

[Chef Shawn]

Re: Mercruiser 140 Manifold Riser Extension?

Yeah, I just went out and double checked, it's what you are looking for. All three ports are open. I would suggest you replace you impeller as well if you are running at 185 degrees, I have to run my 140 really hard to get it to top 150 degrees.

 

[nrasnake]

Re: Mercruiser 140 Manifold Riser Extension?

Chef I sent you a PM.
I'm looking at the single piece replacement riser above and notice it only has two mount holes, but there are four bolts on the manifold. How can that be? Aren't these risers prone to leaking with four bolts... I would think two bolts would be worse. If anybody has used these single piece risers or has any info I would appreciate it. I'd like to get things ordered soon so I can get everything back together.
Thanks!

 

[nrasnake]

Re: Mercruiser 140 Manifold Riser Extension?

For anybody interested in the BARR Marine manifolds, I just received my new one today from Engines1 and it is in perfectly new condition and contains all of the mounting hardware and gaskets. They currently have the MC-1-99798 on clearance for $163 (tax & shipping included!). They must be cleaning housing because that's a steal.

Westerbeke, Victron, Algae-X, Energy1, Webasto & Other Marine Power Parts & Sales

Cheers!