2015 Suzuki DF25A Idle Revving Problem

[flyguy90]

https://www.youtube.com/watch?v=lK7W_0g8OFk

Starts fine, idles fine until you give it gas, Then it acts as you an see in the video. Is it misfiring? The boat runs well in gear except you can feel it acting a little funny at higher throttle. Was tuned up not too long ago tho.
Running 93 ethanol free gas.
Does this seem to be a fuel issue? Or spark?
Seems to be using more gas than it should, especially for a clean burning 4 stroke.

[Moonlighter]

Seems like it may be the neutral throttle limiter kicking in. Bit hard to be sure because we only saw a very short video. But your description suggests that might be the reason.

These engines have an electronic protection system that prevents over-revving when they are not in gear. Prevents them being revved past about 3000rpm in neutral.

The system cuts spark, reduces fuel, and basically it runs pretty much like what your short video shows. Like a race car with then pit lane speed limiter on!

So that would likley explain what is happening when you are attempting to rev it up when it is in neutral. Solution is easy - dont rev it up in neutral! LOL!

When it is in gear and running at higher throttle, is it doing something similar? If so its possible you may be hitting the rev limiter. Possibly under-propped a little.

Do you have any way to check the rpm’s?

Just a note - Its always a good idea to run a water separating fuel filter in the line from the tank to the engine - the Racor style ones with a clear bowl are a popular choice. These engines, with efi pumps and injectors, do not like dirty fuel so such a filter should be a standard fitting if you want to prevent expensive fuel system issues.

[flyguy90]

Seems like it may be the neutral throttle limiter kicking in. Bit hard to be sure because we only saw a very short video. But your description suggests that might be the reason.

These engines have an electronic protection system that prevents over-revving when they are not in gear. Prevents them being revved past about 3000rpm in neutral.

The system cuts spark, reduces fuel, and basically it runs pretty much like what your short video shows. Like a race car with then pit lane speed limiter on!

So that would likley explain what is happening when you are attempting to rev it up when it is in neutral. Solution is easy - dont rev it up in neutral! LOL!

When it is in gear and running at higher throttle, is it doing something similar? If so its possible you may be hitting the rev limiter. Possibly under-propped a little.

Do you have any way to check the rpm’s?

Just a note - Its always a good idea to run a water separating fuel filter in the line from the tank to the engine - the Racor style ones with a clear bowl are a popular choice. These engines, with efi pumps and injectors, do not like dirty fuel so such a filter should be a standard fitting if you want to prevent expensive fuel system issues.

The weird thing is that it starts doing whats in the video as soon as I give it gas. It doesnt even get a chance to revv up at all. But if that is what it is supposed to do then Im fine with it.

It has a fuel seperator on it. Its a yamaha one so its not clear but seems to be in good shape. Maybe just need to replace.

When Im at higher throttle, it just doesnt seem to be getting anymore umph, just making more noise haha. My skiff is only 275lbs and at about half throttle itll do about 25 mph and then if I give it the rest of the throttle it only gets to about 27mph. Again, might be normal, it just seems to be using a lot more engine to not get much more speed.

As far as gas mileage, looking at the map, looks like I may have done 20-23 miles today on the boat and used about 1.5-2 gallons. About a 1/4 of my tank so maybe I really shouldnt complain.

[Moonlighter]

Its not normal to have an engine behaving like that if the throttle is gently increased to just above idle - as I said, it is designed to kick in at about 3000rpm to prevent damage to the engine by excessive revving when it is in neutral.

But if you crack open the throttle and hold it there, then it will activate the over-rev protection system instantly and it will sound just like it did in the video.

So i guess that you are the only one who knows how much throttle it has been given.

Maybe another video showing it running at idle and gently accelerating might throw more light on the issue.

So when it is in gear, are you saying that you can accelerate away and its got good strong acceleration, and is not misfiring?

If that is the case then it would not indicate a problem with either fuel of spark, as typically either of those issues would get worse with the engine under load, not better.

You could buy one of those simple inexpensive “tiny tach” tachometers from ebay and it should give you a better idea of what revs you are getting.

[2014DF25ARS]

I have a DF25AR (remote control) on a 275 lb aluminum runabout. When I cruise at around 3/4 throttle (23-24 MPH @ 4000-4500 RPM), I get 15-17 MPG. When I run at WOT (29-30 MPH @ 5900 RPM), I get 10-12 MPG. That last bit of throttle really costs you in fuel economy.

On the remote-controlled motor, I can’t apply throttle without putting the motor in gear, except for a separate “fast idle” lever. It doesn’t take much throttle to hit the 3000 RPM limit that Moonlighter describes, at which point the motor starts missing and generally running like poo, till you back down to a reasonable idle.

[raven71]

My df25a had idle issues from day one. After the motor would get warm it would not return to idle. It was very dangerous as I had to go at such a high rpm through the marina to get back to the dock and then shut off the motor and drift/paddle to the dock. The rpms would be so high you could not shift the motor into neutral. Not fun or safe in a river with fast current. After the motor would sit it would idle fine until it ran for a while. Sometimes it would idle so high in neutral it would hit the rev limiter. The dealer said he couldn't find anything wrong so I took a video. The dealer had my motor for over two months and said they replaced some parts regarding the throttle. The motor did exactly the same thing on the first trip. After months of no answer Suzuki was absolutely no help. They didn't seem to care so I purchased a Yamaha. A week later the dealer said Suzuki told them to replace a plastic part that was swelling up due to heat and that should fix it. Suzuki waited months and months to finally suggest a fix after the dealer repeatedly asked for guidance. They expected me to be a guinea pig and keep testing a dangerous motor. I wasn't impressed at all with Suzuki or the dealer.