Our MerCruiser Exhaust Buyers Guide is a comprehensive list of things to look for and consider before making a purchase. We will cover every aspect of the purchase to make sure that you are happy with the products that you order. Please read carefully.

When is it time to replace my exhaust?

We suggest changing OEM Exhaust parts every 5 years to be safe. OEM MerCruiser manifolds and riser elbows can last more than 5 years in salt water if properly cared for, but, every year over 5 years on a salt water application is a gamble with the life of your engine on the line.

We have seen fresh water applications last upward of 10 years.

Aftermarket parts usually last about half as long, depending on the brand and quality.

We suggest removing the riser elbows and replacing the gaskets every two years. This will give you the opportunity to do an internal inspection and catch the problem before it hurts your engine.

What are some signs that my exhaust needs to be replaced?

Seeping around the manifold to riser gasket area.

Rust or water leaking around the gasket area can mean that the gasket is wearing and starting to leak. Leaking on the outside doesn’t hurt things as much as it just makes it ugly, but when its leaking outside there is a good chance that water is starting to leak into the exhaust jacket in the manifold as well.

Rust in the exhaust ports.

Once the manifold is off of the engine you can look in the exhaust ports. There should be no signs of water or rust at all.

Mismatched riser temperature.

Carefully check the temperature of your two riser elbows. They should be approximately the same. If you notice one side running much hotter than the other, there is likely blockage somewhere in the exhaust system. It is a good idea to take the risers off and do an internal inspection.

Comparing Replacement Brands and Coatings

OEM vs Aftermarket

As always, we urge our customers to use OEM parts. When it comes to manifold parts, you really get what you pay for.

GLM We had to stop selling these parts due to quality control issues

Sierra is a higher quality aftermarket part, but is not far off from OEM in price.

Barr parts are great and similar to Sierra in quality, but most parts are overpriced compared to sierra, so we do not stock them.

OEM E-Coated vs Ceramic

MerCruiser offers their manifolds in either ceramic coated or E-coated. In our opinion, the ceramic coating is not worth the large price increase. MerCruiser’s ceramic coating offers a slightly stronger resistance to wear, but from our experience it doesn’t extend the life of the parts by much. MerCruiser’s E-coating is the same paint coating used on the exterior of their new engines, it is certainly sufficient. If the price was close we would go for it, but when doing an entire exhaust system it is a difference of several hundred dollars.

Wet Joint vs Dry Joint - Skip for engines older than 2001.

In 2002 MerCruiser switched from wet joint manifolds to dry joint. This refers to the passage in the manifold in which the water flows through.

In a wet joint manifold the water passes through small ports directly connected to the exhaust gas port.

Dry joint manifolds move the water away from the exhaust port to an external port. there are no longer holes near the exhaust gas port.. This helps protect the engine in the event that an exhaust gasket or part fails.

Notice the gasket for the wet joint riser. The walls are very thin.

The dry joint riser pushes the water ports far away from danger.

Is my dry joint riser elbow 7 or 14 degrees?

MerCruiser made 2 different dry joint riser elbows. 7 degree from 2002-2004, and 14 Degree from 2004 until today. If you are on a cutoff year and you are not sure which one you have, you can check the casting number on the riser itself. & degree should say “864309” and 14 degree will be “864591”. If you cant figure it out just give us a call and have your engine serial number handy.

Which Riser gasket does my engine need?

Which Riser gaskets do I need?

MerCruiser offers 3 different types of riser gasket. Full Flow, Restricted and Block Off

Wet joint 
27-863726 Gasket – 4 Slot. “Full Flow” Commonly used with 3 and 6 inch riser spacer blocks.
27-863724 Gasket – “Restrictor” (with 2 small holes and 2 slots). The 2 small holes always go fore and aft. These are the most common for raw cooled engines.
27-863725 Gasket – “Block-off” (without holes or slots). This gasket stops coolant flow.” Common for closed cooling systems.
Dry joint
27-864547a02 – Full Flow – Both holes open. – Commonly used with riser spacer blocks.
27-864850a02 – Restricted – One hole open , one hole closed. – These are the most common for raw cooled engines.
27-864549a02 – Closed – Both holes blocked. – Common for closed cooling systems.
The only safe way to know which on you need is to take your riser off. Parts lookup programs are often incorrect!

Torque Specs

Some people will say different, but these seem to be the most common numbers.

33 lb-ft For the riser

20 lb-ft for the manifolds

One Piece 4.3 Exhaust

Mercury used a “one piece” manifold on the 4.3 v6 in the late 90s. If you have this set up you must convert to the newer style 2 piece exhaust. We made a kit to make it easy for you.