225 4stroke running rough

[bfoxg8r]

Hello

Engine details:
2019 Merc 4 stroke 225
Serial #2B692086
Just over 100 hours
Service up to date

Last week this engine started running poorly. Felt like it's missing a cylinder or two. Would only get to about 3600 rpm.

Its showing no alarm codes on the vessel view display.

I checked plugs, and they look great.

It's going to be a while before my dealer can see it. Anything else I can check in the meantime? Will his computer show more than just the vessel view codes?

Thanks!

[Mrxlh]

Fuel filter is where I would start, the new design has been a problem on the V6/V8 platform.

[ourflat]

My pontoon boat have a similar issue and wasn’t throwing any codes either. After I installed a fuel water separator I discovered the problem was water in the fuel tank. This fall I pumped all the fuel out of the tank and vacuumed all the debris that was choking the fuel tank pickup. I also replaced the fuel tank poppet check valve on the tank.

The fact that you’re not throwing codes leads me to believe your problem is similar to what I had with my Merc 115HP 4S.

Frank

[bfoxg8r]

Just changed fuel filter a month ago. Fuel water separator looks clean.

Any other ideas?

Thanks

[ourflat]

Do you have a poppet check valve on top of your fuel tank from the internal pickup tube? I purchased an external fuel pump from auto parts store to troubleshoot my problem. When I hooked up the fuel pump to drain my tank I could see the fuel line restriction.

[EuropeanAM]

Just changed fuel filter a month ago. Fuel water separator looks clean.

Any other ideas?

Thanks

They're one and the same in most cases, should not be multiple filters involved.

Visual inspection is wise... check for damaged plug wires, disconnected plug wires, etc.

Beyond that, the Basics: Compression, Spark, Fuel Quality/Delivery/Pressure, and G3 CDS Printouts/Diagnostics.

[bfoxg8r]

I do have a separate fuel / water separator between the tank and engine. It was installed by the dealer when he hung the engine. I'll do one more thorough visual inspection.
Thanks for the help.

[EuropeanAM]

IF a separate filter is installed in the boat, the filter UNDER the cowling is supposed to be removed, and replaced with a bypass fitting.

Remote Water Separating filters should include wiring for Water-in-Fuel notification.

[thommo59]

IF a separate filter is installed in the boat, the filter UNDER the cowling is supposed to be removed, and replaced with a bypass fitting.

Remote Water Separating filters should include wiring for Water-in-Fuel notification.

Don I’m keen to understand why this is? I have both.

[SilverFox579]

Adequate filtration already exists under the cowl and additional filtration is not recommended as it can cause fuel restriction. Same protocol existed with the Optimax.

[EuropeanAM]

+1

In addition to the obvious performance-problems that can develop with a fuel supply restriction: Engine damage caused by fuel supply restrictions is not a "defect" in the engine.

[thommo59]

Thank you

[bfoxg8r]

Just an update. Got it into the dealer. It was a bad plug wire. It looked good when I inspected it, but I guess it wasn't.

Thanks again for all your help