Does Your Yamaha Outboard Head Gasket Need to be Repaired?

Do you believe that your Yamaha outboard head gasket is in bad shape?

Your Yamaha outboard head gasket is a very important component in the performance and lifespan of your engine. Located between the cylinder head (where your spark plugs are screwed in) and the cylinder block, a head gasket is responsible for sealing these components together to withstand the compression from the engine and enable cooling water to flow between the block and the head.

Like most outboard components, parts age through usage and time. Head gaskets that are regularly exposed to excessive heat, corrosive saltwater, and other substances will eventually reduce the integrity of the gasket.

However, if a head gasket is not replaced when it begins to fail, water will begin to enter the engine. Once this happens, the performance of your outboard will be significantly affected and eventually lead to major engine damage.

To avoid this, there are a number of telltale signs to look out for when it’s time to replace your Yamaha outboard head gasket, including:

1. Reaching the 4-Year Mark
2. Low Pressure in the Cylinders
3. Water Coming Out of a Spark Plug Hole
4. Black Specks, Crud, and Slime in the Cylinder
5. Idle Runs Too Slow or Rough
6. Holes In the Head Gasket

1. Reaching the 4-Year Mark

To ensure your Yamaha outboard performs its best and to extend its lifespan, preventative maintenance should always be a top priority. Yamaha recommends a number of regular maintenance intervals for your outboard based on its usage - 20 hours for a new engine, every 100 hours or annually, and enhanced service at 300 hours and 500 hours.

However, one common benchmark for Yamaha outboard head gasket replacement many boaters miss is replacing it every four (4) years. Depending on your usage, this timeframe may be shortened but four years is generally regarded as a “must” to change your head gasket before other problems develop.

There may be no visible signs of head gasket damage by this time, but this repair will give you peace of mind - plus, when you’re changing the head gasket, you can perform other inspections and replacements (such as anodes, engine bores, salt/sand buildup, spark plugs).

2. Low Pressure in the Cylinders

Another common sign that your Yamaha outboard head gasket is in need of repair is low pressure in the cylinders. This requires a simple compression test on each cylinder, which involves removing each spark plug, plugging in a compression gauge, and cranking your engine without giving it throttle (PartsVu’s guide for compression testing).

What you’ll be looking for as you test each cylinder is near-identical readings between cylinders. If there’s more than 10% variance between each cylinder, it’s likely that the head gasket is the culprit.

3. Black Specks, Crud, and Slime in the Cylinder

If you notice black specks, a blackish crud, or a grey slime in the cylinder, it’s more than likely that a leaking head gasket is to blame. The reason for these substances is that combustion byproducts build up in the combustion chamber during combustion. These byproducts then either flake off (specks), build up inside the cylinder (crud), or mix with water from the adjacent cooling chamber (slime).

4. Idle Runs Too Slow or Rough

When idling, especially at low RPMs, you may notice that your engine runs too slow - almost to the point of completely dying. Or, it may provide a rough idle that’s not consistent, causing a jarring motion.

The reason for these events is that the spark plugs cannot create a consistent spark due to water leakage on the spark plugs. If you remove the spark plugs and notice corrosion, then water is leaking in and diluting the fuel due to a faulty head gasket.

5. Holes In the Head Gasket

If you’ve managed to remove the cylinder head, it’s important to inspect the head gasket itself. The head gasket should not have any holes where it makes contact with the cylinder head and the engine block, as well as the areas around it.

However, this may require cleaning the gasket of any sand or salt that’s penetrated and accumulated around the gasket to get a clear visual of the problem. It’s common when removing this debris to discover that it was intermittently plugging and eating away at the gasket material (and parts of the cylinder), causing an intermittent problem.

Unfortunately, not catching this problem in time can lead to serious repairs to the cylinder head and other affected parts - all of which can be very expensive and require professional work.

Frequently Asked Questions (FAQ) about Head Gaskets

Can you replace a head gasket yourself?

Yes, a head gasket repair is an easy job that only requires a few tools. Unlike a vehicle, where getting to the head gasket requires the removal of the engine and other components, an outboard is smaller and easy to access.

How much does it cost to replace a head gasket on a boat?

If you choose to replace your Yamaha outboard head gasket yourself, you can only be on the hook for parts ($50 or less for many engine models) and tools (many of which you may already have in your toolbox).

Taking your outboard to a mechanic will include the cost of parts, but also labor. Considering labor generally costs between $70 - $120 (or more!), the total cost of just a head gasket replacement can be a few hundred dollars. Of course, the advantage of a head gasket replacement by a mechanic is that they can make other replacements, trim the heads if they’re warped, and diagnose any other developing issues that may be plaguing your Yamaha outboard.

Is a head gasket worth fixing?

Yes, a head gasket is a worthwhile investment that can prolong the life of your entire Yamaha outboard motor. Better yet, you can learn an essential maintenance skill and expand your knowledge base, both of which will pay you dividends in the future.

* * *

Now that you understand the most common signs that your Yamaha outboard head gasket may need replacing, it’s time to grab the parts (and some elbow grease) to perform this relatively simple repair. PartsVu has everything you need to replace your Yamaha outboard head gasket and much more, including a full line of T-H Marine boating essentials. Shop for your parts today!

***

This content was designed to serve as a general guide. Persons who are not familiar with marine engine repair and who have not been trained in the recommended servicing or installation procedures should have the work performed by an authorized marine mechanic. Improper installation or servicing of parts can result in engine or boat damage, personal injury to the installer, or harm to persons operating the product.