SWS II 200hp Stalling and alarm- Pls HELP!

[MacGyver83]

Hi All-

Thanks in advance for any help/insights with this outboard issue... I've read lots of threads here but I seem to have a unique problem... Sucks

History on the boat/motor:
- new to me last fall
- good even compression at time of purchase
- winterized
- Ran it in a 50 gallon drum at home for an hour at varying throttle and ran beautiful. Started first turn

*Current issue:*
Starts up first turn and sits nicely at idle for about 2-3 minutes.
Then stalls out.
When trying to start after stall, alarm on key sounds.
Leave it for 15-20 minutes and it will start but runs rough and then after 30 seconds to a minute stalls again. Leave it for a day, it starts up fine for 2-3 minutes then dies out again. After I did the first round of cleaning filters etc, it ran at idle fine for about 20 minutes.

The block doesn't even get more than warm to the touch. And the water is streaming so the water pump appears good.

Here's what I've done:
- Added 25 gallons of new fuel (tank was 1/4 full)
- Replaced fuel separator filter
- Replaced fuel filter @ motor
- Replaced VST Filter and gasket
- Cleaned Injector filters
- Added fuel stabilizer
- Checked plugs
- Visually inspected all vacuum lines etc

So any ideas?

My yard can't service it for 2-3 weeks so I'm hoping I can narrow in on the issue and fix it myself.

My next moves are:
- LP fuel pumps
- Clean O2 sensor
- Clean Pressure Regulator Filter @ VST
- Thermostats?
- Pressure Test VST? (need to buy pressure kit)

Thanks again guys- hopefully I can return the favor some day either on the forum or on the water!!

[rodbolt17]

only way it will alarm at cranking is if the ECU sees both a cranking signal AND a stop signal at the same time.

if you have 10 gallons of bad gas and add 25 gallons of fresh gas you will have 35 gallons of trash gas.

at speeds below about 1200 RPM the fuel pump circuit is through the resistor, drops pump voltage to about 9 v.

excessive rail pressure will cause rich running.
loss of rail pressure will cause lean running.

if the stbd side T stat sticks open it will run rich.

[MacGyver83]

Update: the keyswitch / tether switch is faulty.
Just goes to show to start with the simple things!

Thanks for the help.