jet sizes on modded yam 50hp w/ 70 carbs

[vStrandell]

Hi,

My name is Victor, I'm from Finland. And 18 yrs old and I am very interested of race boats.

I have a Yam 40/50hp two-smoker on a 15feet v-hull boat (Marino Swing, check out the MarinoSwingCup on google, awesome boat racing here in Finland).

Im tuning the engine now under the winter, and the block is getting ready (higher ports). It will also have lowered head, tuner, CCMS reeds etc.

I will put 70hp carbs on it, and my question is what jet sizes I should start from with the 70 carbs. Especially the ide jet size wonders me, the main jet I will seek for the best one in the spring. Any suggestions on jet sizes?

Thank you for any help,

Happy new year,

/Victor


Picture of the block, not yet finished, only raw grinding done this far.