need some help

[booger man]

I have a 1997 sylvan proselect f/s rated for 150hp with a 1978 merc 115 2 stroke ...I have two vortex al props in 19 and 17 pitch ...The 19 runs per gps at 44 mph at 5000rpm and it will ventilate at max trim ( the rpm went up but i didn't notice the tach) the 17 pitch got 41 mph also at 5000 rpm but i could trim it all the way up without ventilation ....the cav plate is 1.5 inches above the deep v keel ...shouldn't my rps have gone up ? also what would a ss prop do for my set up compared to my al and what brand and pitch would you recommend ?

 

[booger man]

Re: need some help !

Re: need some help !

anybody

 

[Silvertip]

Re: need some help

Prop recommendations are very subjective. Two props with the same diameter and pitch can perform very differently. The 17 pitch didn't raise RPM over the 19P because it may have been a more efficient prop meaning it had less slippage. Remember that a prop works in a fluid (water) so only the prop guru's that design them fully understand all the dynamics. The AV plate is apparently about right. Hard to say what a SS prop would do. Generally they are more efficient than aluminum so slight drops in RPM from an aluminum prop of the same spec can be expected. Sorry this isn't much help but I suggest you work with a dealer. If they know you are serious about a purchase they will generally let you try several props to help you find what you need.