Prop Wizard accuracy?

[Tinlizzy]

...I decided to try the prop wizard, for getting me in the right range for a new prop.

This prop is for a 1971 1150 Mercury (115 hp) fitted on a 19' Marquis closed bow. The hull is a semi-v. This motor has never ran on this boat before. There are no trim tabs, or PTT. I should be hitting 4800-5300 RPM for this motor. The gear ratio is 1.78:1.

The wizard recommended a 19 pitch for water sports and a 21 for speed. Does this sound correct?

 

[jackyack18]

Re: Prop Wizard accuracy?

I'm no expert on this at all but to give you some guidance I have a 1970 renken tri hull with the 1150 tower of power on it with a 19p prop and it shoots my boat out of the hole with no trouble and will run about 35-36 mph at WOT. (guessin about 7000 rpms) My tach might be off but thats the reading im getting....speed is accurate lowrance gps confirms this. I am looking for a prop that would give me more of a top end so im thinking about switching to a 20" or 21" prop becuase I have a ton of hole shot and it seems as if the motor is just torquing the boat around and never seems to be bogged down! It all depends on the weight/size of your boat! From reading on this website the best guidance I got was to just expirement! But then again im just a rookie, I hope I was of atleast some help to you!

 

[JoLin]

Re: Prop Wizard accuracy?

I tried prop wizard and give it a THUMBS DOWN.

I gave it engine model and year, told it I was running at 5200 rpm at WOT (300 rpm below mfr's WOT spec) and it still told me to go UP in pitch. Worthless.

Instead, I went from aluminum 17p to stainless 15p, and that put my WOT rpm right where it should be @ 5500 rpm.

 

[JoLin]

Re: Prop Wizard accuracy?

I'm no expert on this at all but to give you some guidance I have a 1970 renken tri hull with the 1150 tower of power on it with a 19p prop and it shoots my boat out of the hole with no trouble and will run about 35-36 mph at WOT. (guessin about 7000 rpms) My tach might be off but thats the reading im getting....speed is accurate lowrance gps confirms this. I am looking for a prop that would give me more of a top end so im thinking about switching to a 20" or 21" prop becuase I have a ton of hole shot and it seems as if the motor is just torquing the boat around and never seems to be bogged down! It all depends on the weight/size of your boat! From reading on this website the best guidance I got was to just expirement! But then again im just a rookie, I hope I was of atleast some help to you!

There's no reason to "just experiment." You need a few basic facts:

1. Pitch of current prop.
2. Motor manufacturer's WOT throttle rpm recommendation for your motor.
3. Actual WOT rpm with normal load
4. If possible, actual speed measured by GPS

Finally, any specific goals you have (increased top end, better hole shot, more efficient mid-range cruising, etc), and/or any specific issues you want to resolve (stern heaviness requiring more lift, for example)

Get that info together and post it here. You'll get advice.

 

[BMOLCHANY]

Re: Prop Wizard accuracy?

I used the wizard to get a new prop for my 40 Johnson and it worked out perfect.