0:00
Hello, and welcome to the Born Again Boating YouTube channel
0:04
Today we will be going through the proper and most effective way to troubleshoot a rough
0:08
running 225 Mercury Optimax. This process is extremely similar to almost all Optimax models
0:15
Hopefully this video helps you out. If it does, don't forget to like it and subscribe to the channel for more helpful videos
0:21
Make sure and ask us any questions you have in the comments section below and enjoy the video
0:27
Before getting started, make sure there is good clean fuel going to the engine
0:31
Then the first thing that you want to do when troubleshooting or servicing any Mercury Optimax
0:35
is to split the bottom cowling. There are only four 5-16th inch bolts holding it together
0:41
Two in the back, one in the front outside here, and one in the front inside
0:46
Don't try and skip this, it will make this experience 100 times better
0:50
Also, be careful with the wires in the front here, then don't forget to disconnect the
0:54
trim switch. Now we can carefully remove the spark plug wires and then the plugs
1:00
Pay close attention to what they look like and what cylinders they came out of
1:04
On certain models, a couple of the ignition coils will need to be removed to get them out
1:09
You'll need a spark tester and a remote starter switch for this, but we'll start by checking
1:14
spark and compression. Compression is good to do while you are here, and between the spark plugs and the spark
1:19
test, we can rule out half of the possible issues. We will need the key switch on for the spark test, but off for the compression test
1:27
And for this particular engine, the spark test reveals that two ignition coils are not
1:32
firing properly. A quick test is to just swap whichever coil is not firing with one that is
1:38
This could be the problem, it's a very common issue. If not, we'll move on to the pressure tests
1:44
This is the air pressure valve, and here is the fuel pressure valve
1:48
We need to see both of these pressures at the same time to accurately diagnose the issue
1:53
We are looking for the fuel pressure to be at 90 psi and the air pressure to be at 80 psi
1:59
Some Optis have a higher pressure at 110, but that 10 psi difference between the two
2:04
is key. If the pressures are the same, then the tracker valve on the starboard rail is leaking and
2:10
needs to be replaced. Remember that an OptiMax has a fuel injector that shoots the 90 psi fuel into the 80 psi
2:17
air and through the air injector. These two injectors work together to atomize the fuel into the cylinder
2:24
With the gauges on the engine and it idling, we can then pinch off this fuel hose here
2:29
and see if the air pressure spikes. If it does, that's great. Then the same for this air dump line here
2:35
If it does, perfect. If not, then we know where we need to start testing
2:40
Like on this engine, if the air doesn't jump, then this usually indicates a weak air compressor
2:45
Air compressors are not cheap and you definitely want to get a professional to double check
2:49
your diagnosis before spending the money and replacing it. It is important to understand that the fuel pressure is a little trickier because if the
2:57
engine does not have the correct air pressure, then it will not produce the fuel pressure
3:02
Note also that there are fuel and air regulators on the port rail that regulate these pressures
3:07
If the spring or one of these fails, it can also cause the air pressure not to spike
3:12
Even a stuck open air injector can cause you issues and a misdiagnosis of the compressor
3:18
so make sure you know what the problem is before buying an air compressor
3:22
If you are trying to test this in your driveway, another test to perform is a drop test
3:26
Do this with the engine running and disconnecting a spark plug wire to determine which cylinder
3:31
is not firing. You will hear and see the engine stutter when you do
3:35
If nothing changes, there's an issue with that cylinder. If you are suspecting an injector, remember that both of them are super expensive, so
3:42
you can try swapping a suspect one with one of the others that are on that same fuel rail
3:48
These are your basic troubleshooting tests that can be performed and most of the time
3:52
will show what is going on with the engine. Sorry we don't have time to go into depth on say cleaning the VST or starting issues
3:59
In most cases though, this should be enough to get you going in the right direction to
4:03
figure out what exactly you are looking at which is causing the poor running condition
4:08
of your Opti. If you have a specific question, drop a comment below and don't forget to like the video and
4:13
subscribe to the channel for more how to tutorials
