Lower Pitch?

[aced19]

I just bought a 92 Bayliner Classic. At WOT 17" Solas SS prop with four adults (750 lbs) rpm 4,800. Speed is 31 gps. I know from what I've read thats within specs on rpm. But when pulling a tube with 500-600 lbs of people in boat the rpm hits 4,000-4.2000 rpm WOT. It feels a little sluggish on the hole shot. So would I do better with a 15" prop to help with hole shot? or whats your thoughts on better performance.
BTW motor is a mercruiser I/O 3.0
Prop also is 15 1/4 X 17

 

[SkiDad]

i would think 17 pitch is correct for what you want to do - but the diameter is high - i would think you would be running something like a 14x17 - that will get your rpm up some. I would look at a 17 pitch in 4 blades - i think that would do it. 15 is probably going to be too low of pitch and over-rev. I also would think your speed would be close to 35 with a 3.0 and a 17- so i wonder if it needs a tune up

 

[aced19]

Thanks for the help.
Now another question.
How much rpm will I gain by dropping to a 14 diameter from a 15 1/4?

 

[SkiDad]

I'm just guessing but I would think about 200 rpm with something around 14.5x17 3 blade - it you went 4 blade it might be a wash

 

[jestor68]

Your present numbers indicate a 21% slip factor; not likely. Something else is wrong.

Your speed with a 2.0 gear ratio and 17 pitch prop using a reasonable 10% slip should equal about 4200-4300 rpm and you are showing 4800.

No doubt you require about 2 inches less pitch, but get the tach working right first.

Your Bayliner should have a plastic connector on the back of the tach. Pulling it off and cleaning the pins might get it working right again. You should see a lower rpm reading; something like mentioned.

Stick with the big diameter less pitch formula for good pulling power with your 2.0 gear ratio.

Something the Solas Amita 15-1/4 X 15 should get the rpm up to the 4600-4700 range and pull stumps.

 

[aced19]

The tach could be off. I'll clean it this weekend and see what the reading is.
Thanks everyone for the help.