mmillward26

I was doing some testing on my new boat that I got about a month ago. It is s 1986 Sea Ray Pachanga with a 350 Mag Alpha 1 outdrive combo and a 23p prop.

Yesterday, I managed to get a top speed of 57.4 mph with an rpm of 5200. According to engine specs, I should only run between 4200 - 4600 tops. What direction should I go with the prop to bring this down?

thanks

verbi69

If you add more pitch you will bring the rpm down.

mmillward26

How does the pitch affect performance? Is more pitch going to increase or reduce top speed? And the affect of top speed will be the opposite of getting out of the hole correct?

Griff

Every 23 pitch prop is not the same. What model prop???

A 2" increase in pitch of the same model prop is good for a 400rpm reduction. Spinning a 350 mag at 4800 is not a problem.

mmillward26

It is a 23p Mirage Plus - the number 48-13704 is stamped on the side of it. Thanks for the info!!

blkhorse

iTrader: (1)

I would check the accuracy of your tach. I have a baja 220 sport with a 350(mildly built) with an alpha running the same prop and can only get 4800 at approx the same speed(58.2 full of fuel, 4 people) 5200 at 57 is about 24% slip,quite a bit I think.

Tow-N-One

I had a 87 pachanga 454/330 horse alpha SS same prop 4600 RPM was 67.3 GPS. I am pretty sure it was a 1.5 ratio drive. I would check the tack. What are you using for a speedo?

mmillward26

I was using a handheld GPS for speed accuracy. Secondly, how do I check the accuracy of the tach and is there a way to determine the gear ratio without pulling the drive apart?

Tow-N-One

The ratio should be on the sticker on the drive. My fluke multimeter has an rpm function on it that is pretty accurate. Some timing lights can do it also.