Suzuki 150 surge or lose power at 3K RPM

[karelfish]

Hi everybody!
I'm having issues with my Suzuki outboard. It's 2008 and 500hrs. It worked fine las year and after sitting for 1 month (in December) it started to lose power at 3K
I have 2 videos.
VIDEO 1: https://www.youtube.com/watch?v=Ed1co5Z_878
As you can see in the video is working fine at idle speed (same from idle to 3K)

But sometime after 3K it start to lose power randomly
VIDEO 2: https://www.youtube.com/watch?v=xrEKJjcONBY

I cleaned all fuel system (except tank) but I changed
- water separator filter (new)
- low pressure pump
- fuel filter
- pump squeeze
- hose (from the pump squeeze to high pressure pump)
- I also opened high pressure pump and was really clean and everything looks OK

Any idea??

[karelfish]

This 2 pictures are form high pressure pump (immediately after open it) so I did't clean it

[BowansReward]

Just to point out if you are revving the engine in neutral, the engine will limit your revs at 3k. There is a neutral detector switch/sensor designed to protect the engine, putting it in "limp" mode.

The limiter is designed to let you get home by running at no more than 3k revs. If you rev the engine in neutral it has the effect of oscillating above & below 3k as there is no load.

[karelfish]

Just to point out if you are revving the engine in neutral, the engine will limit your revs at 3k. There is a neutral detector switch/sensor designed to protect the engine, putting it in "limp" mode.

The limiter is designed to let you get home by running at no more than 3k revs. If you rev the engine in neutral it has the effect of oscillating above & below 3k as there is no load.

OMG! Can't be true .. yes in neutral! I tried before go fishing and noticed the issue but never tried on the sea. Will do a test this weekend (in the water).

However, it's not 'limiting' to 3K (in second video). It's more like going to 3200 then back to 3000, 3200 again, 3000 (oscillation). But I will try anyway at the sea.

[BowansReward]

OMG! Can't be true .. yes in neutral! I tried before go fishing and noticed the issue but never tried on the sea. Will do a test this weekend (in the water).

However, it's not 'limiting' to 3K (in second video). It's more like going to 3200 then back to 3000, 3200 again, 3000 (oscillation). But I will try anyway at the sea.

That was the second point that I made. The limiter is designed to work under load (in gear pushing the boat). With no load (neutral) revs shoots up past 3k revs, the fuel is limited & drops back down & drops below 3k, the limiter stops & it shoots back up. As you say it oscillates. I've seen exactly that on my engine.

[Moonlighter]

The neutral throttle switch prevents the engine being revved past about 3000 rpm in neutral, so it cant be damaged by people who dont know what they are doing,

Ever heard a race car engine when its going down pit lane with the pit lane speed limiter activated? This is the same.

The ecu cuts fuel supply, interrupts spark, reduces spark advance so when you push it to the limit it surges, kicks and farts and runs bad.

So stop trying to rev it in neutral!!! No point in doing that.

[karelfish]

That was the second point that I made. The limiter is designed to work under load (in gear pushing the boat). With no load (neutral) revs shoots up past 3k revs, the fuel is limited & drops back down & drops below 3k, the limiter stops & it shoots back up. As you say it oscillates. I've seen exactly that on my engine.

Yes, always tried in neutral after siting for 3 months I did the test (after changing filters). Unfortunately I sent videos to some experimented people and nobody mention the "neutral" switch. Thank you!!!

[karelfish]

The neutral throttle switch prevents the engine being revved past about 3000 rpm in neutral, so it cant be damaged by people who dont know what they are doing,

Ever heard a race car engine when its going down pit lane with the pit lane speed limiter activated? This is the same.

The ecu cuts fuel supply, interrupts spark, reduces spark advance so when you push it to the limit it surges, kicks and farts and runs bad.

So stop trying to rev it in neutral!!! No point in doing that.

That's exactly what it does: kicks and farts and runs bad.

My presumption was (based on my limited experience) a fuel issue and because I never did maintenance in fuel lines I did the whole "schedule maintenance.
Will keep everybody posted after do a test in the ocean!!! Thanks!