Question on exhaust flappers

[1985mariner20]

I have a I/O with a mercruiser 357 motor and a VP duoprop outdrive. with this combo, there are no flappers in the exhaust system. I am currently doing a complete rebuild due to the engine sucking in water through exhaust valves when it died in the ICW. My question is, Where/how would I add exhaust flappers to the system. some systems have them in the Y pipe(my Y pipe doesn't have the holes to install flappers), some systems have the flapper in the exhaust bellow between they pipe and the out drive( I would like to not have to remove my outdrive if possible). Can anyone point me in the right direction for maybe adding them in between the risers and y pipe? Any help is much appreciated!

Motor is a 2013 merc 357 5.8L 325HP
Outdrive is a VP dp-s1 "SX"

 

[alldodge]

I have a I/O with a mercruiser 357 motor and a VP duoprop outdrive. with this combo, there are no flappers in the exhaust system. I am currently doing a complete rebuild due to the engine sucking in water through exhaust valves when it died in the ICW. My question is, Where/how would I add exhaust flappers to the system. some systems have them in the Y pipe(my Y pipe doesn't have the holes to install flappers), some systems have the flapper in the exhaust bellow between they pipe and the out drive( I would like to not have to remove my outdrive if possible). Can anyone point me in the right direction for maybe adding them in between the risers and y pipe? Any help is much appreciated!

Motor is a 2013 merc 357 5.8L 325HP
Outdrive is a VP dp-s1 "SX"

Have any room to raise your elbows with spacers, or change to higher rise elbows?

 

[Thalasso]

^^^^^ Would be the best way

 

[1985mariner20]

I've got some room to play with there. How high above water line do risers need to be to be safe?

 

[JaCrispy]

drill holes for flapper hinges?