prop venting question

[turnerlittle]

i have a 70hp 1976 model evinrude and i was wonder if there is a precise way to determine how big to drill the vent holes i believe the prop to be a modified 15p with a diameter of around 13in any help will be greatly appreciated

 

[PROPer]

Re: prop venting question

Are you having trouble getting on plane? What are your RPM @ WOT?

 

[turnerlittle]

Re: prop venting question

its really slow to plane but not so slow i would consider it the engine it may have been set up wrong i've read several statements about the cavitation plate needs to be above the transom it wasn't but i felt like it should come out faster considering approx dry hull weight was 750 the boat doesn't have a tach or i would tell you but i don't feel like i'm over revving it and my and my father had two tritons that had vents we toyed with but they were the pvs system on merc 200s

 

[PROPer]

Re: prop venting question

The vent holes will probably get you on plane a bit quicker, but I don't know of an exact way to detmine the correct size. I guess I would start with smaller holes and work my way up if I needed to.

 

[turnerlittle]

Re: prop venting question

thank you i think i will start with an eighth hole