Manifolds and risers; terminology and cost

[Gunn]

So I read a lot about having to regularly check and/or replace manifolds and risers. I assume this is the exhaust manifold on each side of V6/8 engine. I assume the risers are what attach to these to get the exhaust out of the boat. Am I correct? :huh:

Then, I'm looking at a 1996 240 Sundancer. Wondering what it costs to have these replaced? Do the manifolds usually need replacing at the same time as the risers, or do each fail/wear independently? Just looking for a general cost estimate on what you guys think these run. I'm trying to figure if this boat is worth it or not, assuming it would need these replaced, but not knowing 100% for sure, yet.

Thanks,

Tom

 

[Dave S]

Here is a parts illustration of a typical Mercruiser exhaust system.

Some motors are fitted with risers (shown to to the right in the illustration as NSS) between the manifold and the elbow (identified as part number 11). Notice the slotted holes on the various components and gaskets. This is where sea water circulates to keep everything cool as the exhaust gases pass thru the center. It is also where corrosion can occur. And corrosion many times will form at the gasket areas where these parts are joined. From what others have said, if you run in salt water you should inspect these components at least every two years. In fresh water they should be inspected when the boat is 5 years old and then every two years thereafter. It involves unbolting all the components and then making a decision if things look OK or not. If the components look OK, then clean up all the mating surfaces, put on new gaskets, and retorque all the bolts. Here are some typical prices on all the components shown above. This was taken from http://mercruiserparts.stemtostern.com/

1 32-44348001Tube - Exhaust
(standard) 2 $54.10 $40.58
2 54-815504272Clamp 8 $1.85 $1.65
3 11086TElbow - Exhaust (port)
W/o Risers 1 $153.75 $138.36
3 14343TElbow - Exhaust (starboard)
W/o Risers 1 $163.85 $147.47
3 14801A1Elbow Kit - Exhaust (use With 3 in. and 6 in.
Riser Kits) 1 $327.35 $294.62
4 54-815504272Clamp 8 $1.85 $1.65
5 32-14358001Tube - Exhaust 2 $54.50 $40.88
6 807130A4Pipe - Exhaust 1 $507.10 $456.38
7 807166A1Shutter - Water 2 $42.50 $38.25
8 25-807167Grommet 4 $1.10 $0.83
9 10-58640Screw (3/8 - 16 X 1 - 1/4 in.) 4 $3.40 $2.54
10 13-41471Lockwasher (3/8 in.) 4 $0.95 $0.69
NS 19-8079923Cover - Hose Clamp As Required $0.35 $0.26
11 861776A2Plate - Block Off
(thru Transom Exhaust) 1 $42.75 $38.47
12 10-98794Screw (3/8 - 16 X 1 in.)
(thru Transom Exhaust) 4 $2.10 $1.58
13 13-41471Lockwasher (3/8 in.)
(thru Transom Exhaust) 4 $0.95 $0.69


As to your other speciifc questions, I will let others with more expereince than me answer them for you but this ought to get you started.

 

[H2ONUT]

I replaced my manifolds and riser/elbows a few months back due to overheating.

I started with the manifolds, the port manifold was plugged solid with rust, the elbows "looked perfect". It was the opinion of others that looked at them also. Overheating continued.

I replaced the elbows and everything ran much cooler. I had other issues also, but they did need to be replaced, even though they looked OK.

I used GLM parts. I found them from a guy in New Jersey on E-Bay. Perfect fit and fast shipping and priced right. New OEM Mercruiser parts are almost double in price.

I did all the work myself. You'll need an extra set of hands, or cut 2 pieces of threaded rod to help support and guide on the manifolds. They are HEAVY! Took me about 4 hours to remove and replace. Also added new hoses and a t-stat while I was in there.

 

[Gunn]

Guys thanks for the quick replies. Dave, I went to Stem to stern and took a look at those diagrams and such for a 1996 5.7L (which this boat has). Great info. So it looks like to replace the standard items, Manifolds, risers, elbow assembly, its around $1,200.00. Wow. And they only last 3-5 years? :smt101

Does that sound "ballparkish"? If I'm missing anything in that cost, let me know.

 

[comsnark]

Yes. About $1200 IN PARTS. Add a pile of labor if you get a yard to do it. Also, it is not uncommon for bolts to be corroded severely. This could easily be a $2000-$2500 job at a dealer.

 

[Nehalennia]

Yep, I paid around $3200 for mine to be replaced in '05

 

[jellyfish]

Try looking at www.ebasicpower.com they have after market parts at very resonable prices.. GLM and OSCO. Both brands are very good.

Alex

 

[Gunn]

With that kind of money, its definately a DIY job for me, rusty bolts and all. :smt001 If it wasn't for my DIY skills, I couldn't afford to own a boat!

Thanks again for all the info.

 

[wickeral]

I'd like to add a bit to this thread. When purchasing your Manifolds and Risers spend a little more money and get the Ceramic coated products. The coating is on the inside and will add years to your Exhaust System. Also, many times the Cylinder Head Bolts will be rusted so badly they cannot be removed by a standard socket wrench. If yours show signs of rusting replace them at the same time before they reach this critical condition. It's a Pain but it is a good PM effort. Al W.

 

[H2ONUT]

I spent $417.00 for manifolds and risers, came with the mounting gaskets. A new t-stat $23.00. 4 hoses for $68.00. Outdrive water pump kit $50.00. Circulator pump on the front of the motor $90.00. 2 new belts $27.00.

Adds up to $675.00, which included the shipping) Just went thru the receipts.

Manifolds and risers (E-Bay, they are GLM and are coated on the inside) T-Stat (West Marine) Hoses (ebasicpower.com) Circulator pump (NAPA Sierra Marine) Belts (NAPA Sierra Marine)

Labor was my time, about 6 hours total.