You can research the market but you can’t find any lighter outboard motor in the 150HP direct 4-stroke category.
There are lots of good features and specs of it. But I have seen lots of people complaining about the outboard motor’s issues.
So, I have listed the most common problems with Mercury Optimax 150 to help you solve yours. Let’s get started right away.
6 Most Common Problems with Mercury Optimax 150 Outboard:
1. Starting Problem
The motor can show problems in the initial starting stage. Symptoms can vary based on the production year.
One user mentioned that his Optimax 150 sputtered slightly while getting on the plane. It lost almost 200 RPM at that time.
It happened even after running ethanol-free gas almost 80% of the time.
After a thorough checkup in the servicing shop, the mechanic found that there was a leak in the vapor separator.
For a safe and permanent solution, he added seafoam, replaced the faulty vapor separator, and changed the main fuel line along with the primer bulb.
The problem was sorted out for the time being. However, after a second check-up, the mechanic found out that the motor was maxed out at 4600 RPM.
Then, running a $900 computer test, showed no error codes; only the max RPM is lower.
When the customer changed his 23” propellers with a 19” one and used quickleen, the performance improved dramatically. He noticed 5400 RPM while going into the wind and 5300 RPM against.
Furthermore, one should check the coil and other engine parts for this issue. Finding any corroded or clogged part needs to be cleaned or replaced for better speed and smooth performance.
2. Electrical Issues
Due to the problem in the electrical system, you may notice some unusual warning messages on the dashboard.
One of the users mentioned that he suddenly saw Temp fault, oil level fault, TPS fault, mat fault, sensor fault, and some other warning signs going off all at once.
Sometimes changing the connections and cleaning the plugs can solve the issue. And, sometimes the problem continues to occur.
In such a situation, you should read the owner manual carefully and see whether the settings are in the right mode.
I have seen a user telling complaining about getting lower voltages down to 1V messing up the sensors. You should keep that fact in mind too.
3. Alarm Problem
It is kind of similar to the previous one. But the diagnosis and the solution of the problem are a lot different.
The complainee told that the Optimax 150 2007 model had 4 beep alarms going off without any visible problem.
After spending a whole summer and almost $1000 in the shop, the problem still existed.
Initially, the mechanic identified it as the problem of voltage drop. Cleaning the wire and terminals, replacing the battery, and doing a sea trial, the mech told that the problem was gone.
Once the user took it for a spin, the alarm took off again repeating every 2 minutes.
According to another user, it was solved after replacing the tank and sensor. The troubleshooting process involved purging any air from the engine and unplugging 2 wires from the oil sensor.
4. Cold Start Stalling Problem
Older models of Optimax 150 DFI have an issue of cold start stalling. When you start the engine, there is no problem.
Right after, the engine dies even when there are no fault codes. Some users have mentioned that trying to start the motor 10 times or more, it runs perfectly warm and doesn’t die.
Before signing up for an expensive ECU test, you can try some troubleshooting by yourself.
Firstly, try replacing the temp sensor. Because the users who were facing the issue did it.
Heating the sensor with a hot gun lets the engine start and run perfectly. And, freezing causes the problem like the way mentioned above.
Also, check the fuel injectors and see whether they are clean or not.
5. Overheating Problem
Some units can show overheating warning signs while running the engine at 2000 RPM or higher. Changing the impeller may seem like the solution.
Yet, some users have reported that the issue exists after replacing the component twice in 4 months.
In other troubleshooting methods, you can try checking the water pump or the pump tubes. See if there is any sand in there.
In some cases, running the motor at higher RPM cools it down.
Furthermore, you can try replacing the pump housing because it can wear the impeller off sooner than it is supposed to.
6. Water Pressure Problem
You may face an issue with the water pressure. The SmartCraft gauge would indicate it.
In this case, one can replace the water pressure sensor, poppet valve, thermostat, and water pump to see if anything changes.
One way to know whether the sensor has gone wrong is by grounding it to the block and notice any change in the gauge reading.
You should also look for any kind of blockage in the water channel to the heads. It is possible that the telltale is in good condition and still there is no water going to the heads.
What Majority of the Users Feel About Mercury Optimax 150?
There are mixed reviews and opinions about the Mercury Optimax 150. Some people are happy with its performance and some are not.
You can see from the problems discussed above that it can be frustrating to face all those issues.
Also, I have seen some bad customer service experiences reported by the users.
The older models are buggy and have lots of design issues. That is why customers don’t feel confident about them anymore.
However, you can talk to your dealer and ask for honest opinions. Knowing the performance of the recent units can be different.
Those who want a strong and economical outboard engine can go for it. Indeed, there are some problems with Mercury Optimax 150.
But no other model in the 150HP category is perfect.
It is highly likely that you would face the problems within the warranty period. Once they have been fixed, you will be able to use the engine for years.