yup, thinking this electric antisiphon ss mentioned in this tsb
P/N 862733A 1
https://stu-in-flag.net/blog/wp-cont.../vaporlock.pdf

https://www.ebay.com/itm/112819504556

and what is it for? I always wondered and asked, nobody could answer me... how does an anti syphon works? but again, I never had any problem...

it replaces the soring loaded in a barb fitting one mist all bats have. Suction (which electric pumps aren’t good at) opens these. Ie: inches if vacuum.

An electric one is an open/closed electric valve. No suction needed to open it.

Temp remaining same, The more psi fuel is under, the less likely for vapor. In other words, less psi fuel is under, the more likely for vapor to form. Most liquids act the same. Think coolant and why added psi is helpful vs none or low.

Here is one of the bulletins from merc that gets into good details on this:
https://www.perfprotech.com/blog/art...ser-vapor-lock

i would seriously consider putting in the merc recommended electric booster pumps and dumping those mechanicals. Mechanical pumps dont put out much pressure or flow at idle since motor isnt turning fast. Electrics run same pressure and flow at all times. Its an easy DIY project and last i checked you could get kits for both motors for about $1400 if you shop around.