How to Clean Marine Exhaust Manifolds (The Best Way)

Written by Shawn Buckles in Maintenance

It is imperative to have an exhaust system for your boat that works very efficiently. Over time, your exhaust manifolds are going to encounter various issues. They will rust and become dirty due to regular use and this is going to necessitate some type of cleaning.

How do you clean your marine exhaust manifolds, though? You need to take the manifolds off of your boat and give them a thorough scrubbing. It may be a bit of a nuisance to have to remove the parts from your boat entirely but this is going to be the best way to get them clean. You will be able to use cleaners on them and scrub off any of the debris off while you have them off of the boat.

Taking the time to clean your marine exhaust manifolds can be quite beneficial. It will allow you to have a better experience overall and things should work better than they have been. If you do not clean your exhaust manifolds semi-regularly, then they may become gunked up. This could lead to various issues and you do not want to encounter problems while out on the water.

Join me as I take a look at exactly how you should go about cleaning your marine exhaust manifolds. You will be able to feel more confident about the process and should have no trouble getting the results that you desire. The whole step-by-step cleaning process will be explained and it should be simple to do this for just about anyone who owns a boat.

Old man works on boat engine

On this page:

  1. Cleaning the Marine Exhaust Manifolds
  2. Other Potential Cleaning Methods
  3. Why it’s Important to Clean and What Happens If You Don’t
  4. When Should You Replace the Marine Exhaust Manifold?
  5. Conclusion
  6. Related Questions

Cleaning the Marine Exhaust Manifolds

1. Remove from boat

In order to get started, you are going to need to remove your marine exhaust manifolds from your boat. This may involve taking the risers off first and things can differ a bit depending on your setup. Generally, you are going to need to remove the bolts that connect the riser as well as removing any exhaust hoses. This should allow you to disconnect the exhaust manifolds.

Remember to wait to remove the exhaust manifold until everything has cooled down. If you were out using your boat within the last hour or so, check to make sure that the exhaust manifold is cool. You do not want to accidentally burn yourself or cause any other type of injury. Everything should be cooled down within thirty minutes of turning the boat off.

2. Clean them with a scrub brush

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. You should be able to use this method to clean the entire marine exhaust manifold and it will come out looking much nicer than before.

Of course, your goal is not really to make the manifold look nice. You want it to function well and you are removing any debris for this reason. Anything that has built up will be able to be removed and everything should work much better as a result too.

3. Reinstall the parts

Once you feel that it has been sufficiently cleaned, you will be able to take the time to reinstall the parts. This should not take too long nor should it be overly difficult. Just be sure to install them back on your boat properly and test all of the connections to make sure that things are tight. Remember to place your exhaust hoses back on and fasten the screws properly as well.

Other Potential Cleaning Methods

There are some other potential cleaning methods that you can make use of as well. Actually scrubbing the marine exhaust manifold is seen to be ideal by most but you can go other routes if you prefer. One popular method to help clean up an old, dirty exhaust manifold is using an acid bath.

Acid bath - An acid bath should be able to remove many of the problems that are present in your marine exhaust manifold. This is also very simple because it is a passive cleaning method that you can take advantage of. Just remove the part and place it into an acid tank of some sort. This will allow your exhaust manifold to be cleaned up and the results are usually pretty good.

If you are looking for a way to take advantage of this method, then you will want to contact a local auto body shop. Many of them will have tanks that you can use for a price to give your part the acid bath that it needs. Either way, calling and asking some questions will prove to be beneficial. You may want to call the same auto shop that does the work on your car as they will be more likely to give you the time that you need.

Sandblasting - This method may sound as if it is too much of an inconvenience for some people to want to bother with it, though. Another option that some have made use of is sandblasting. This may not work perfectly as cleaning the inside of the marine exhaust manifold with a sandblaster will prove to be difficult. It can still be a viable option to consider.

A good sandblaster is going to be able to remove any dirt, debris, and rust from the exhaust manifold. Sometimes these sandblasters may be too harsh and could damage a weak manifold. If your manifold is very rusty, then replacing it was likely the best option anyway.

Why it’s Important to Clean and What Happens If You Don’t

If you don’t take the time to clean your exhaust manifolds, then they will not last as long as you would like. These parts can generally last between three and five years. Depending on the type of water that you are taking your boat out in, these times can vary. Cleaning the manifold regularly can ensure that it will perform well and that you will not have issues while out on the water.

When your marine exhaust manifold goes out while you’re on the water, it can leave you stranded. Depending on the severity of the issue, it could hinder the performance of your vessel or it could cause problems with the engine. In the worst cases, you may need to call for help.

Being a diligent boat owner is going to be in your best interests. Just taking the time to check your parts and to make sure that things are working well is smart. It should not take too long for you to do this and you will be able to make changes when necessary. Sometimes a simple cleaning can keep things running well for quite some time.

In general, cleaning a marine exhaust manifold is not going to take up a lot of your time. It can improve the performance of the manifold by keeping it from getting filled up with debris and having other problems. Just a small amount of time can make it so that you will have a better time while out on the water.

You also need to keep in mind that cleaning your marine exhaust manifold is not always going to be the answer. This is a helpful and intelligent thing to do but sometimes a part will simply need to be replaced. You also need to be able to recognize when it is time for a new part.

When Should You Replace the Marine Exhaust Manifold?

Most marine exhaust manifolds are going to be able to last for between three and five years. These numbers can vary quite a bit depending on the type of water that it is exposed to regularly. Knowing this, it is smart to start keeping a closer eye on your exhaust manifolds after the two-year mark. Regular cleaning can somewhat extend the life of these parts but they will need to be replaced over time.

One of the reasons why they need to be replaced is due to rust. Rust is going to weaken this part significantly and it will eventually become unusable. Removing the rust is not always going to be the best way to go. It could leave you with nothing but thin metal and this is not going to work well as an exhaust manifold.

Knowing this, you should be ready to replace a marine exhaust manifold when it is getting older and appears to be quite rusty. You can look for signs that it needs to be replaced so that you will know for sure. One good method is to reach inside of the manifold to check for hot spots. Hot spots will be a sign of internal corrosion and this means that it is time for a new exhaust manifold.


Taking the time to clean the manifold is going to be very worthwhile. It can keep it so that the part is operating efficiently. This will allow you to avoid problems while out on the water and you will have a better overall boating experience.

There are times where the part is simply going to need to be replaced, though. Learning to differentiate between when you can clean the part to improve it and when it is ready to be replaced is crucial. Look for the signs that a marine exhaust manifold is on its way out and everything should be fine. Regular cleaning will always be useful but you simply want to go about things in the most intelligent way depending on the situation.

How long do Mercruiser exhaust manifolds last? Mercuiser exhaust manifolds last approximately 3 - 5 years with intensive use. Using original OEM manifolds will increase the life span to 5 - 8 years. Saltwater use will dramatically reduce the life expectancy: to about 3 years.

Did you find the answer to your specific question?
👍 1 👎 1


Challenger Marine Exhaust

Great piece of information, Thank you for sharing the updated one..

Leave a comment