What does a exhaust manifold do on a boat?
It collects the extremely hot exhaust gasses directly from the engine into an inner “pipe” or long chamber which is usually cooled by raw water running through an outer casing. From here the hot exhaust gases and water are fed to the riser where the gases and water combine to continue their trip overboard.
Why do jet boats have water cooled exhaust?
The exhaust exits through rubber hose and has to be cooled so it makes sense to use the water when it exits to cool the exhaust.
How does a marine exhaust riser work?
All marine inboard engines have exhaust risers. The exhaust riser has two functions: (1) to keep water from backing up into the engine through the exhaust piping and, (2) it serves as the device that introduces cooling water into the exhaust exit piping system.
How long do manifolds and risers last in freshwater?
Check risers and elbows starting at two years, and annually thereafter, if the boat is used in salt water. Even with a closed cooling system, the risers are raw-water cooled. Risers usually fail before manifolds do. Risers and manifolds used in fresh water have an almost indefinite life.
Why does water come out of the exhaust on a boat?
Water-cooled inboard engines inject cooling water into the exhaust pipe, which cools the exhaust and muffles engine noise. The exhaust then pushes the water out the exhaust pipe. This is known as a wet exhaust system.
Can you weld marine exhaust manifold?
The cast iron boat manifolds were pre-heated to 450 degrees in oven for 2 hours. We used a PowerCon 350 DC welder at about 70 amps, and welded 1 inch at a time. Immediately after the 1 inch of weld, we “shot peened” with air hammer and pointed chisel. This removed the slag and left the surface of the new weld dimpled.
How long do risers and manifolds last?
Good-quality risers last on average 4 – 5 years in saltwater, and 6 – 8 years in freshwater. Exhaust manifolds will last on average 6 – 8 years. Saltwater use may reduce the life span to 3 years. Light use in fresh water may increase the life span to up to 20 years.
How do you clean a marine exhaust manifold?
With the exhaust manifold removed, you will be able to start cleaning it. Grab yourself a scrub brush and then apply some type of lacquer thinner to it. Scrub the manifold vigorously so that you can remove built-up debris and any type of rust that has started to form.
Are boat exhaust underwater?
Typically, underwater exhaust is what is normally referred to as “exhaust exiting” through the bottom of the boat, but in some cases, underwater exhaust could also be exhaust exiting at the transom or the side of the boat that is below the waterline.
Can you JB weld exhaust manifold?
JB Weld ExtremeHeat is perfect for making repairs on all manner of high-heat parts, including exhaust manifolds, mufflers, catalytic converters, exhaust pipes, engine blocks, fireplaces, smokers/fireboxes, and many more crack-prone items.
Can you fix cracked exhaust manifold?
Unfortunately, there’s no quick-fix for a cracked exhaust manifold. Some drivers have attempted to use heat-resistant epoxy, such as JB Weld. While JB Weld is an amazing product with hundreds of uses, it simply can’t withstand the 1,200-degree exhaust gases.