2020 DF175 Loss of power

[Brendonp]

DF175 that has a loss of power when running at full throttle. The motor starts, runs and idles fine. It can run on lower RPMs with no issues. Once it reaches WOT or close to it, after few minutes of running the engine will lose RPM and bog down back to 3500. If the throttle is released it will go back to normal idle. It will then perform normally until run at full RPM again. It doesn't have any fault codes at all

The local suzuki dealer are unsure of what it is. The repairs are all under warranty. So far they have inspected and tested the fuel system on the outboard. They assure me the ships fuel system has no issues (Im not 100% confident they have checked it thoroughly) they replaced the VST and other fuel system parts. No change

They have recently just put a new ECU on and also no change

Now they are looking at replacing the VVT

Just hoping someone out there has maybe experienced this issue before and could provide some insight. It's now been 4 weeks of the dealership throwing parts at it with no luck

Cheers

[redlowrey]

Has it got a throttle cable or is it electronic throttle control, will make a big difference in the diagnosis of the problem.

[Brendonp]

Throttle cable

[artdf175]

sounds like a fuel starvation issue
usually don't start replacing parts until you have exhausted all the basic things first..
as you can see replacing parts is not working
sounds like at wot fuel is being restricted.
two immediate things come to mind..
fuel tank not breathing correctly or at wot the fuel line is sucking air through a coupling
does the fuel bulb collapse when this happens?
watch the fuel filter for air bubbles-
Art

[Brendonp]

My suzuki dealer has been replacing all these parts under warranty. They have no idea what the actual issue is. They've just changed parts and hoped it will work. So I thought I'd reach out incase someone has had a similar issue.

I definitely agree with you art. Fuel starvation. The dealer keeps assuring me that They've tested the ships fuel system and its okay. But they haven't tried hooking up a new fuel tank and line to rule out the system.

As for the primer bulb. Yes I have noticed it collapse

[redlowrey]

If you had a problem in the fuel system your Suzuki dealer should have been able to see the fuel trims being changed bye the computer to compensate for the engine running lean and adding injector on time to compensate.
They can see the live data through the sds, they can see what is happening with the variable valve timing and everything they need to see to make a diagnosis, something does not add up.

I think the people that are working on your engine have got no idea. Parts changer’s.

[Brendonp]

Redlowrey you are dead right about them just being parts changers! They have no clue. Only using them as it's under warranty.

They aren't able to replicate the fault when the boat is on the trailer. So having to do a sea trial each time they change a part is slowing the process a lot! Does the suzuki diagnostic tool allow you to connect it and see live data whilst being on the water?

[Moonlighter]

Red is right. SDS disgnostic system can be plugged into the engine while the boat is underway.

But the primer bulb collapsing could be a big clue….

That is usually indicating a problem such as the vent line being blocked or even partially blocked, or something like a fuel line between tank and bulb being poor quality, deteriorated internally, or simply too small diameter.

Find the vent outlet and see if mud wasps have made a nest inside there. Blow thru it with the tank cap off and see if there is free flow of air. Make sure there isnt a kink in it somewhere that is restricting airflow.

If in any doubt of the fuel line between tank and primer bulb, replace it. Old lines can be damaged internally by ethanol fuel of they arent designed to cope with it. The damage may not be visible from outside.

Also lots of US boats have those anti syphon valves on the tank outlet and they can cause fuel restrictions and starvation if they fail or malfunction. Take it out and replace with a simple barb, they are not needed and are just a problem waiting to happen anyway.

Or, the filter between tank and primer bulb might be partially blocked, I would replace the element just to be sure.

Beyond that, the tank pickup could be partially blocked - but thats a bigger job and best left until all other things have been eliminated.

These are all things you can do/check yourself. And of course none of them are caused by the engine.

[Murray]

Check the fuel line where it enters the engine through the rubber grommet. If the fuel line is run through the wrong hole it could be getting squeezed.