should I get A 21 or 23 pitch prop

[Chris Hiscock]

I have a1998 yamaha c115 hp with a 19 pitch prop, at wot I am running 6000 rpms and 45 mph.I feel this is to high for the rpms,I think the max is about 5500 rpm for this engine is this correct?I feel a 21 will may be drop my rpm,and give me more speed.does any one know if this wouldbe a good selection,or would a 23 pitch be too much.from this info do you think the 21 would be my best selection.Thanks Chris

 

[Bondo]

Re: should I get A 21 or 23 pitch prop

My Guess is,......

The 23" prop would be Too Much..........

 

[CalicoKid]

Re: should I get A 21 or 23 pitch prop

I would think 20" or 21" would be good depending on setup. What kind of prop is on it now (brand-model) ? They're all different. If you get a lot of additional lift out of a different prop you might be able to add more pitch and get more speed without losing too much RPM. You may also be able to raise the motor with the right prop and gain efficiency there. Got a pic of your boat showing the motor and transom? I would think you'd want to be turning 5500rpm minimum at WOT definitely not less. I believe everyone is shooting for around 5800rpm on carbed 2 strokes these days.

You will get a much clearer answer and suggestions if you give more detail on your boat. The make/model, current prop, engine height, a pic or two, current performance re: holeshot and handling etc. I agree you will probably have a hard time turning a 23 unless your boat is very light and the setup is currently very inefficient.

 

[propper_advice]

Re: should I get A 21 or 23 pitch prop

your max rev range is 5500 rpms so with that 19 pitch your way out of your motors range at 6000 rpms. i strongly urge you to go up in pitch to a 23 because with ever pitch raise by two you typically get 400 rpms taken of your wide open rpms, so the 21 pitch isn't going to cut it. You are going to need to double up on the pitch to a 23 to get into your motor's original rev range which is 4500 to 5500.

-nick