Exhaust Manifolds - The Silent Killer
All marine engines have water cooled manifolds.
In our opinion, exhaust manifold failure is the #1 killer of marine stern drive and inboard engines.
Manifolds and mixing elbows that are sea water cooled can last about 7 years when the boat is moored in the water. If the boat is stored out of the water, on a trailer or in dry storage, the life expectancy is about 5 years; this outcome (shorter life span) is caused by extra oxygen occurring in the manifold which increases corrosion.
The exception to a conventional manifold is the MerCruiser dry-joint manifold which was introduced in 2002. This new design moves the flow of water away from the gasket surface that joins the manifold and mixing elbow and prevents water, either from seawater or condensation, from finding its’ way into engine components thus extending the life of the manifold by several years.
The most common exhaust manifolds are made of cast iron. Cast iron mixed with salt water flowing through them, combined with the heat from the combustion chamber in the engine, causes the manifolds and mixing elbows to corrode.
When an exhaust manifold fails, due to corrosion or gasket failure, salt water runs into the cylinders when the engine is turned off. At this point, highly corrosive salt water causes damage to the cylinder walls, pistons and the intake and exhaust valves, all of which add up to heavy repair costs.
The best solution to avoiding expensive repairs is to inspect the manifolds and mixing elbows as part of your on-going maintenance schedule. The cost of inspection is very little compared to the cost of having cylinder heads repaired because of damaged valves; or worse yet, having to replace a complete engine due to piston failure. Honestly, we see this happen too frequently when it can be easily avoided.
Adding this inspection into a regular maintenance schedule will not only avoid costly repairs, but also assure that your engine is good to go when you are, which is especially helpful in a seasonal climate such as ours.
Give us a call us today for more information at
(604) 921-7124. We’d be happy to talk with you.
