2003 DF70 Surging when given throttle

[fingerscrossed]

Hello all,
I'm new to the forum, and new to Suzuki ownership. I picked up an 03 DF70 with ~650 hours. Ran great on the water for a few day but when I took it out last night I experienced the following issues:
Idled fine out of the channel where we store it, but once I increased throttle, it started surging and shaking in an oscillating manner and I got single beeps every ~6-10 seconds from the throttle. When I backed off the throttle down to minimum wake (to limp back to the dock) the beeping eventually went away. Revving up in Neutral produces the same result.
I've been reading as much as I can about it, and our plan is to do the following in order:
Replace gas tank (possible venting issue)
Replace fuel line and bulb (both are old but not visibly cracked)
Install in-line fuel filter
Check spark plugs
Replace internal high pressure fuel filter
Anything else anyone can think of right off the bat? Would replacing the high pressure fuel filter be a doable job for an outboard rookie but mechanically inclined person?
All of these will be tested with brand new gas too, as there is naturally some concern about water in the fuel causing the issue.

Thanks a bunch for any help/tips.

[fingerscrossed]

Got the tach hooked up and it appears it first starts to surge/shake around 3000 rpm. maybe 2900

[Moonlighter]

Likely to be a failed neutral throttle switch (NTS). Its located on the engine attached to the gear linkages. This switch prevents the engine being over-revved in neutral.

The NTS sends a signal to the ecu to tell it when the engine is put in gear. If the switch is broken, no signal sent which means the ecu still treats the engine as if its in neutral, and then it limits revs to about 3000rpm and to do that, it cuts spark, limits fuel supply and ignition advance. So the engine runs bad when it hits the limit, exactly as you have experienced.

The switch is not expensive or difficult to replace. And yes, they do fail occasionally.

[fingerscrossed]

Hi all, we were able to replicate the issue with the tach attached and were finally able to see that it was an overheating issue occurring around 5000 rpms. This narrowed down the options quite a bit. We took off the water intake vents and cleaned out them out good and our problem has disappeared. Thanks for the suggestion on the NSS/NTS, I read so many different threads where people were having issues with similar symptoms. I'm glad ours ended up being a simple fix.

[Murray]

I would replace the water pump assembly unless you know it was done recently by the previous owner. Cheap insurance.