Rough Idle 2010 Honda 150 HP O/B

I have a 2010 Honda 150HP Four Stroke and this past season the engine would start right up and idle smoothly at approx. 800 RPM. After about a minute of running smoothly engine begins to shudder and shake as if starving for gas,
but does not stall out. When I raise the RPM to about 1000 engine runs smoothly. Engine performs well at all other
speeds. At the beginning of last season HP/LP gas filters were changed and also filter/water separator was changed and I add Seafoam at fill ups.

Can anyone tell me what I can check to solve this problem.

Thanks,Ron

Your motor needs 3 things to function, air , fuel and spark at idle the throttle body butterfly is closed and the motor needs air then TPS sends a signal to the ECU, , the ECU then tells the IAC valve which has a solenoid valve to open which then bypasses the butter and allows air into the inlet manifold for proper combustion , so check if your IAC valve is working .when you underway on the water the motor then gets its air as the butterfly has opened ,

Take a look at the air bypass valve filter screen. Items 19, 20 & 21 in the link below. Make sure that screen is clean.

Also make sure the throttle plate is clean and is closing all the way. Sometimes a bit of dirt or grime can build on the inside of the throttle body and/or the throttle plate and prevents the plate from closing all the way. This can confuse the ECM at idle.

When was the last time the VST got a thorough cleaning?

UPDATE: the copy paste for boats.net isn't working for me so no link available.

Just go to boats.net , select 2007 and later. Scroll down to 150hp and select. Then open the intake manifold/injector page and look at 19,20 and 21 on diagram.