What is Dry Joint Exhaust?
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What is MerCruiser Dry Joint Exhaust – History
The term Dry Joint Exhaust refers to MerCruiser’s patented exhaust system which utilizes 2 coolant passages vs 4, between the manifold and riser that are separated outside of the exhaust gasket. The benefit is that this eliminates the possibility of coolant leaking into the exhaust passages through common gasket failures.
In 2002 MerCruiser changed their exhaust exhaust system strategy by introducing the Dry joint Exhaust into their Marine Exhaust System lineup….(Read More). The term Dry Joint Exhaust is primarily associated with the cast iron MerCruiser Exhaust Manifolds and Risers. The Dry Joint Exhaust terminology was introduced at this time as a way to distinguish and market a better exhaust manifold and exhaust riser against the standard “Wet-Gasket” style of marine exhaust manifolds and exhaust risers common to the marine industry for many years.  The Dry Joint Exhaust System design changes were introduced on both the V6 and Small Block V8 engine models. NOTE: MerCruiser also uses the same 5.7L exhaust manifolds and exhaust risers on the 5.0L, 357 Magnum, 383 Mag Stroker and 6.2L engines. However, MerCruiser never introduced Dry Joint Exhaust to the 7.4L or 8.2L Big Block V8 engines. The specific design changes associated with a Dry Joint Exhaust System required MerCruiser redesigning not only the 4.3L Exhaust Manifolds and Exhaust Risers, but also the 5.7L Exhaust Manifolds and Exhaust Risers as well. These Dry Joint Exhaust Systems also required developing a new, completely different Dry Joint Exhaust Gasket between the exhaust manifold and exhaust riser….(Read More).
What is Dry Joint Exhaust
The benefit of the Dry Joint Exhaust design reduced the risk of water leaking at the gasket between the exhaust manifold and exhaust riser. Not only has Water Ingestion always been one of the biggest problems boaters fight when trying to extend the life of their marine engines, but it’s also been one of the highest cost warranty problems for the marine manufacturers. After MerCruiser introduced the 8.1L 496 Marine Engine in 2001 they quickly realized a significant reduction in warranty claims associated to water ingestion by incorporating an exhaust system design that separated the water passages away from the exhaust passage. It was then an easy decision to upgrade the other engine models to a Dry Joint Exhaust design however it was much more challenging to do it cost effectively as compared to the Dry Joint style exhaust on the 496 marine engine models that utilized a fabricated stainless steel exhaust riser and separate hoses to connect the water from the exhaust manifolds to the exhaust risers.
Along with the new Dry Joint Exhaust on the V6 and small V8 engine models the height and down angle of the exhaust riser changed as well. MerCruiser decided that the overall height of the exhaust riser should be raised to meet the overall maximum height of the engine. Therefore MerCruiser introduced a dry joint exhaust riser which was 1.5 inches taller and also included a 14 degree down angle versus the standard 7 degree. This however then created another issue regarding the use of exhaust spacers. For example when 3 inch tall exhaust spacers were going to be installed along with the taller dry joint exhaust riser, this resulted in the overall exhaust height of that installation being 1.5 inches taller than previous installations that included 3 inch tall exhaust spacers. Therefore MerCruiser was forced to introduce the 1.7 inch tall dry joint exhaust spacer and the 4.5 inch tall dry joint exhaust spacer to account for these installations where the standard 3 inch and 6 inch exhaust spacers were already at a package height limit.
How to Determine if You Have the Short or Tall Dry Joint Exhaust Riser
Short Dry Joint Exhaust Elbow p/n 864309T02Â fits Small V8 s/n range 0M300000 and 0W309999Â (pre 2005 models) – Measures 5.2 from elbow gasket flange to mounting bolt boss pad. SELECT THIS LINK TO VIEW EXHAUST DRAWING.
Tall Dry Joint Exhaust Elbow p/n 864591T02Â fits Small V8 s/n 0W310000 and above (post 2005 models) – Measures 6.7 from elbow gasket flange to mounting bolt boss pad. SELECT THIS LINK TO VIEW EXHAUST DRAWING.
Converting from Wet Joint to Dry Joint Exhaust
If you are trying to replace an older NON DRY JOINT exhaust with the improved DRY JOINT system this is possible, however you will most likely need to use the “Short” Dry-Joint elbow/riser as this will be the closest fit to the old Non-Dry Joint Elbow/Riser being replaced. The p/n for the needed restrictor style dry-joint gasket is 27-864850A02 (select link).
Mercruiser also had 2 different Dry Joint Exhaust Systems available on the 8.1L (496 CID) engines. Select these links to view the differences and associated systems.
Link to …….. V6 Standard Exhaust (serial number 0M614999 and below)
Link to …….. V6 Dry Joint Exhaust (serial number 0M615000 and up)
Link to …….. V8 Standard Exhaust (serial number 0M299999 and below)
Link to …….. V8 Dry Joint Exhaust (serial number 0M300000 and up)
Link to ……..Stainless Riser Exhaust System
Link to………Cast Iron Riser Exhaust System
Link to …….. 8.1L Exhaust with Water Rail
Link to …….. 8.1L Exhaust with W/O Rail
Check out the Complete PPT Marine Exhaust Catalog….View Catalog Products