Going from a 1.50 to a 1.36 is usually about 3" of pitch difference. You will need a 22 or 24 Bravo depending where your rpms were with the 26 and 1.50.
Yo want your rpms as close to 5200 as possible to make the most power on a 500efi. A custom labbed 24 would probably work best.

Thanks Griff,I do not fansy a new 1,50 drive for this boat now so I`ll try with a 24,its a pretty light 27 Rib boat,I got the motor out now for a light 400 hours service with new valvesprings and head gaskets,I did inspect the botom and I`m suprised,no wear to talk aboat on the bearings and pistons was clean with fresh springs,nice motors.
Bjorn.

I got the original old head gaskets,but I used the new style "steel gasket" on a procharger motor I got,what is your opinion around this new gaskets?