6 Most Common Problems with Yamaha 350 Outboard

In the 350HP category, the F350 is a respected name in the industry. People love it for its strong build quality, better design, immense power, and reliable performance.

And, you can understand that it is not a perfect outboard motor. There are some issues with the model.

I have tried to discover and discuss the most common problems with Yamaha 350 outboard motor in this article. Let’s get started.

Most Common Problems with Yamaha 350 Outboard

6 Common Yamaha 350 Outboard Problems:

1. Flywheel Problem

The most common problem I have heard about the F350 engines is the flywheel issue.

The early built units have this problem and Yamaha recognizes it. So, they offer free replacement whenever you contact the seller or service center.

I have seen some of the boating experts commenting on the problem. None of them could pinpoint the cause of the flywheel’s misbehavior.

It can be some sort of strange issue in the harmonic balancer design. It tends to come apart and eventually destroy the powerhead.

This is mostly seen on the Gen 1 motors. Even if you have not faced it, you should do a schedule check and replace it while you can.

After running into an engine problem, check the system, and see the error code.

If it means that there is something wrong with the flywheel, waste no more time and take it straight to the nearest service center.

Running the motor for 300 hours, Yamaha will replace it without costing you anything.

Service Update: The engineers at Yamaha developed an Electrical Control Unit or ECU that is capable of detecting flywheel-related issues.

You can see a message on your gauge whenever the rotor is required servicing. So, you don’t need to be constantly in an alert mode.

2. Cylinder Head Leak

Some of the users mentioned certain incidents involving cylinder head cracks. As a result, water poured into the crankcase.

Even after facing the same issue in several units, Yamaha never revealed the exact cause of the issue.

One can only assume. It can be a casting flaw commonly found in the early motors, or the water may not be drained completely out of the motor.

3. Exhaust Manifold Failure

This problem can let water enter into the crankcase causing some serious damage.

Some experts suspect that the problem occurs due to a design issue.

After changing the manifold design in the second generation of the production, the problem can still be found these days.

So, we can say that the problem is not only in the design.

It would be better if you use antifreeze agents through motors that are stored in the winter.

This procedure can ensure the removal of water from the motor. Therefore, there will be no risk of freeze damage in the winter.

Almost all of the dealers use antifreeze before winterizing the 350s and 300s.

4. Poor Shift Shaft Seal

That is right. Failing such a low-priced component is disappointing. Because you have to take off the whole powerhead to replace it.

You have to make sure that the motor shifts smoothly both forward and backward at the same speed.

There are some symptoms of the problem. You may notice that the shift in either direction is slower than the other one. Furthermore, it won’t go into gear as the next indication.  

5. Powerhead Problem

One of the users said that he had two F350s and the powerhead of one of the engines blew out of nowhere.

Yamaha replaced the first one as it happened within the warranty period. After a few days, the second one had the same problem.

In a similar thread of that customer, I have seen some other users complaining about the same issue.

Some say that the problem was caused due to faulty flywheel. But a thorough investigation revealed that the motor mounts were not strong enough.

After upgrading the mount, the issue was eventually solved. It would be better if the manufacturer had called a service bulletin on the issue.

Therefore, no other user would face the same problem.

6. Water in Oil Problem

According to the complaint of an F350 user, he saw milky oil after running the engine for approximately 1 hour.

The trip was after taking it out of the storage. The customer claimed that he properly winterized the outboard motor.

Although, the motor was not showing any problem. In case he didn’t see it, the problem would never be noticed.

It got complicated seeing the issue occurring again even after changing the oil.

To find the problem, one might need to do a leak-down test. Furthermore, it may require tearing down to find any crack or corrosion in any part.

What Majority of the Users Feel About Cobia Boats?

Most of the common issues are addressed by the manufacturer. That is why customers with the recently build units are very happy.

According to them, F350s are one of the most trouble-free motors in the market right now.

Even after running the outboard engine for over 400 hours, it has been performing smoothly without a single hiccup.

The only thing is that you have to change the flywheel after every 80 hours of running to keep things running perfectly.

What I like about Yamaha is that they stand behind their product, and do whatever they could to solve your problems.

Besides the common issues and complaints seen on the internet, there is a flip side of the story too.

Lots of customers say that they are running the F350 outboard motor without any issue for a long time.

So, yes, there are some problems, and you should not be too concerned about them. They are easily solvable and Yamaha does everything in their power to solve them.

Overall, it is a good investment.

Final Thought

Although there are some minor issues, owners are generally happy about the performance of the Yamaha 350 outboard motor.

Given the chance, they would buy it again. So, you can seriously consider buying one. Or, be happy with the purchase you have already made.

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