How to Replace a Boat Exhaust Manifold

  • 2-4 hours
  • Intermediate
  • 50-75
What You'll Need
Exhaust Manifold
Gasket Kit
Torque Wrench

It is important for your boat exhaust manifold to be replaced every few years, so that it does not cause hot spots within the engine. This will lead to serious internal damage to the engine, which will then mean a costly overhaul or engine replacement. Replacing your boat exhaust manifold can be an easy enough job, if you have the right tools and repair manual.

Step 1: Remove Bolts for Boat Exhaust Manifold

Unlike a car's engine, you have fairly easy access to the boat exhaust manifold. Once the engine compartment is open, you will see the exhaust ports on the side. All that is needed is to remove a few bolts on the exhaust manifold itself to remove it. Use a wrench to loosen the bolts. Once the bolts have been removed, you will be able to remove the exhaust manifold. Make sure to put aside the bolts, so you can use them again.

Step 2: Check Exhaust Manifold Gaskets

When you are changing the boat exhaust manifold, chances are that you will need to replace the gaskets also. However, this is not always the case. Take some time to inspect the gaskets, to see if they are still in workable condition. Check for how they fit, if the holes line up, and if there are any tears. If you notice any, then you will need to replace them.

Step 3: Remove Manifold Gaskets

Removing the exhaust manifold gaskets is the part of the project that will take the most time. You must be very careful when scraping off the material, so you do not ruin the aluminum housing. Use a plastic scraper to remove the small pieces of exhaust manifold gasket. Make sure that you only scrape in 1 direction, to lower the possibility of scratches.

Step 4: Install New Gaskets

Once the old manifold gaskets have been removed, you can install the new gasket kit. Dry fit all of the gaskets, to make sure that the kit you have is the right one for your boat engine. Look carefully at how they fit, and how the different holes line up. Any exhaust leaks will lower your engine's power, so you want to make sure the gaskets fit perfectly.

Step 5: Install Boat Exhaust Manifold

Set the new exhaust manifold in place. Without disturbing the gaskets underneath, place the new exhaust manifold onto the engine. Hold it steady in place, and thread the bolts into the correct holes. Start at 1 corner, and tighten until it is snug. Then proceed to the opposite corner. Continue alternating bolts until they are all snug. Then, tighten them all one-by-one.

Step 6: Run Boat Engine

Once the new boat exhaust manifold is tightened in place, start the engine and let it come to operating temperature. This will seal the exhaust gaskets into place, so they will fill any gaps. Check to make sure there aren't any exhaust leaks. If not, replace the engine compartment cover and enjoy your boat for the summer.