Random overheat alarm 1998 Mercruiser 5.7

[getaway2014]

Engine details
1998 Mercruiser MCM 350 5.7 serial number 0L0161738
Bravo 2 drives. Converted to closed cooling by previous owner

Engine temp alarm randomly going off, I believe due to overheating possibly due to cavitation. Previous owner converted engines to fresh water cooling and added sea strainer baskets. When running air collects in sea water strainer.(See pictures attached).
Pumps seem to pull lots of water
Engine rebuilt in 2016 or 17 by previous own

Maintenance done
Sea water pump impeller has been replaced, tightenened connections on all hoses and replaced themostat and sensor.
Checked and tightened gasket on water strainer.
Both guages read about 170 but dont go above 175, risers are warm to the touch. Generally temp gun readings are acceptable.

We blew an engine last year so prob more sensitive. It had the same

Any guidance or suggestions would be appreciated. (The black in the bilge is an old picture and not relevant now)

Thanks

Adam

 

[Scott06]

@Scott Danforth may have some ideas.

 

[Scott Danforth]

Should not be pulling air

Is the strainer fed by the drive, or by a new and dedicated pickup?

 

[getaway2014]

Should not be pulling air

Is the strainer fed by the drive, or by a new and dedicated pickup?

Scott

Strainer is fed by the drives. The intake appears clear. Strainer is also below the waterline so fills immediately if the cap is removed.

 

[Scott Danforth]

I would look between the strainer and the drive to find your air leak.

I would also invest in two pickup castings