Prop Advice: 1996 23' Sylvan Offshore 4.3 Mercruiser

[ChevyNexus]

I have a Sylvan offshore and I'm having a hell of a time finding a prop for the boat. I've tried two props on this thing and neither prop has given me the desired effect. My first prop was a 14 1/2x19 three blade prop that the boat just wouldn't turn. The second one was a 15x15 four blade Aluminum prop and it just made the boat run like dog at around 28 mph in a calm chanel.

So any suggestions on a prop'?

 

[steelespike]

We need details,lightly loaded wot rpm and gps speed with the 19" and 15" What is the horse power?
Do you know the gear ratio.Sometimes on the leg.Is the boat new to you?
If I had to guess the 19 would be close to what you need. So something other than prop selection is going on.
If you get us those numbers we can tell better what is up.

 

[1216bandit]

I have a 22' starcraft islander which is basically the same boat as yours (you may have a few lbs on me but not much), and I have a 4.3 engine, alpha 1 gen 2 drive.. I just recently went with the solas amita 14 1/2 x 19 and am very pleased with it. In fact I probably could have gone with a bit more diameter or pitch as it will easily pull 4800 rpm with more throttle left and speed at that rpm is 40 mph. The hole shot is great and it gets on plane immediatley. I am far from a prop expert but one would think that you should see somthing close too what I am getting??

 

[steelespike]

Assuming as 1.81 gear ratio a 15" prop at 28 mph is turning about 4100 rpm.
Rpm should be off the scale with a 15" prop.