2013 DF 175 Won't rev past 4000, no alarm

[Shamus]

Hi there.
Righto the issue im having is when reving up thru the range when I try to go above 4000rpm the engine coughs and splutters and the revs drop off then comes good again .It's fine under 4000 ,starts and idles no problem .I've tried running on both batteries then swapped from one to the other thinking maybe a voltage drop could be an issue as ive read somwhere before online ,but made no difference .Also felt the fuel line bulb which was hard therefore thinking it was getting fuel no problem .Now this problem sometimes goes away and I can get full revs out of her then it comes back.
Put it in to have service done(270hrs) and mentioned the problem to the guy ,he told me the fuel filter had a little bit of water in it but the rest of the internal filters looked fine .I thought ok great so I take it for a run and it does exactly the same thing. While im out there I notice the sounder warns me that low volts and turns off so at the time I was running on the port battery so isolated that and ran on starb but again no better .
I spoke to the service guy and he was baffled and said the only way to figure it out was to hook up comp while out on the water .So Im trying to save a few dollars and get some advice incase it might be (hopefully) a easy fix .
Any advice would be greatly appreciated

[Solarman]

If trying to rev in neutral, it has a safety feature to protect the motor from going over 3500 rpms. If in forward and doing the same thing. It might be the neutral safety switch.

Good luck.

[Shamus]

It's only in gear and sometimes it doesnt happen but the majority of the time it does ,so very frusstrating .I'm leaning towards fuel but the service guy reckons all filters fine ??

[Moonlighter]

As Solarman said, the neutral throttle switch could be the culprit. They sometimes break/fail/get loose and this can be a gradual processs that gets worse.

If this switch is the issue, the engine’s ecu will not receive a signal that the engine is in gear, and it will then limit revs to under 4000rpm, the same as it does when you try to rev the engine when its not in gear. It limits the revs by restricting fuel supply, cutting spark and advance. The engine acts like a race car engine when they are driving down pit lane with the limiter on - they spit and fart and miss and generally run badly once they hit the limit, but below that are OK.

Check this switch first, and eliminate it as the porblem before doing anything else. Your service guy should have checked this, its not exactly an unknown issue and its not just a Suzuki issue, affects all efi 4 strokes.

It doesnt throw an error code if this is the issue. Cheap part to replace too.

[Shamus]

Thanks guys for replying. This throttle switch can I find it and check it or the service guy better off doing it ?.