Thread: 2015 Tracker 175 txw w/75merc 4stroke (14X29 2.07:1) prop change 21p to 19p

The lower the propeller pitch, the better your “hole-shot”, or ability to get up to speed very quickly from a standstill. However, this improved acceleration comes at a price: top speed. Lower pitch will cause your engine to reach maximum rpm at slower speeds.
On the other hand, a higher pitch affects your boat performance by delivering greater top speeds, but at the expense of your acceleration or hole-shot. (Warning: lower-horsepower engines can bog down if fitted with a propeller with too high of a propeller pitch. This can cause heavy wear on the internal engine parts, who will have trouble keeping up).
If you’re changing the pitch on a recreational boat, there’s a rule of thumb often used that says each inch of pitch is generally worth 150 – 200 rpm. Lowering the pitch increases rpm and vice versa. So for instance, if you were to lower from a 23-pitch to a 21-pitch propeller, you’ll increase engine RPM by about 400 revolutions.

I seen that same info on a lot of youtube videos and forums. I got the 300rpm increase for 2"p drop but increased wot/ 2mph. Maybe from the prop being 1/4" wider. I never run wot so that didnt really matter, the bow doesn't stand straight up in the air with the 19p is the best part

Originally Posted by bamahound

I seen that same info on a lot of youtube videos and forums. I got the 300rpm increase for 2"p drop but increased wot/ 2mph. Maybe from the prop being 1/4" wider. I never run wot so that didnt really matter, the bow doesn't stand straight up in the air with the 19p is the best part

What Buckeye posted is basically theoretical information. What you originally posted was your actual results. This shows that the change in 2" less pitch is putting YOUR motor more into it's "power band". Basically your motor is now able to utilize more of it's available power based on the drive-line change. Kinda like two people on 10 speed bikes. Same hill, same conditions but each person is in a different gear to achieve the same speed. One person is a power peddler and the other is a speed peddler. All 75hp motors are not the same. Just like all 6'2" 200lb people are not the same. One motor on the line might put out 75hp and the next might put out 79hp, but both are within the manufacturers allowable tolerance.
Shows that actual experience trumps a textbook education.

You have basically been lugging your motor since you purchased it ( not good ) depending on engine you maybe still under the RPM you should be running. What RPM is recommended for your motor if Four stroke I am betting you are still not hitting optimum RPM.

When I read his results, I thought the same thing so I looked it up and now he's right in the "sweet spot" thus why his performance was greatly improved!

Originally Posted by Bricks

You have basically been lugging your motor since you purchased it ( not good ) depending on engine you maybe still under the RPM you should be running. What RPM is recommended for your motor if Four stroke I am betting you are still not hitting optimum RPM.

Originally Posted by NCkenner

When I read his results, I thought the same thing so I looked it up and now he's right in the "sweet spot" thus why his performance was greatly improved!

He is still basically at the bottom end of recommended running RPM of 5,000-6,000, if it was mine I would try to get into the upper half at least 5,500 RPM.

The specs from Merc is 4,500-5,500. He's 300 RPM from the max with a partial load. I'd say that's nearly ideal. Just my opinion though.
Mercury Marine 75hp Four Stroke Outboard Engine

Originally Posted by Bricks

He is still basically at the bottom end of recommended running RPM of 5,000-6,000, if it was mine I would try to get into the upper half at least 5,500 RPM.