---

I’ve decided I need a new prop for my 1989 Super Sport Limited.

It has a classic 2005 75 HP Mercury motor, and I need your advice as to which stainless steel prop would give me the best mid level and top speed.

Right now due to the weight in the rear of the boat, I have to cruise at 4,000 RPM to keep the bow down, and the boat running shallow. I'd like to reduce that to 3,000 RPM.

Thanks,

Steve

---

You don't tell us the basic info needed for propeller recommendations, but assuming the 2005 Mercury 75 two stroke uses the same 2.33:1 gear ratio and has a 5500 RPM redline, I would recommend a 13-1/4" x 17" Stiletto Advantage 4.25.

If you really want to cruise at 3000 RPM instead of 400 RPM, you should consider swapping the 75 HP for a 90 HP Mercury two stroke.

---

Steve,

I have a 1994 75hp Mercury Classic 2-stroke on my 1973 17' Montauk and I tried the 13-1/4" x 17" Stiletto Advantage 4.25. on my boat. To get the performance I wanted I need to have that prop repitched to 19 by a prop guy near me. Now my setup may be different than yours as my batteries are in the center console and I weigh close to 300lbs. My motor sits with the cavitation plate 1.25 inches above the bottom of the boat.

After repitching the prop to 19 this is what I got:
4000 RPM 27.5 mph
5200 RPM 38.5 mph (WOT)

Please note that optimum WOT rpm on the 75hp is 4750 - 5250. The 90hp version is 5000 - 5500.

The discussion on this subject can be found at:
http://www.whalercentral.com/forum/vi...post_29990

It also shows the results from some aluminum props, other prop sizes and recommendations from other people.

Tom sorry if I stepped on your toes here as you are indeed a quality source of information and your recommendations for several other people have been spot on. I just thought I should share my experience.

Regards Tim C.

---

Tim,

No problem. We always prefer personal experience to speculation, and the last Montauk I owned had a Mercury 90 not a 75. That motor was equipped with a 20" Mercury Laser II and hit 5400 RPM at WOT. I was extrapolating from the performance of that boat with my recommendation.

I find your data most surprising. We all know that the Stiletto Advantage will perform like other props with two more inches of pitch. Thus a 17" Stiletto will be like a 19" prop from Mercury.

Now you are telling us you took a 17" Stiletto and had it pitched to a 19"? That means you have the equivalent of a 21" pitch prop on a 75 HP motor where a 20" pitch prop on a 90 HP motor is almost too much. That makes no sense.

One contributing factor might be that your hull is a 1973 and non-smirked. The 1989 Super Sport Limited is a smirked hull and we all know the earlier non-smirked hulls were slightly lighter and faster.

For the record, I do not recommend anybody try to re-pitch two inches on a production prop. It can be done but you do not end up with the equivalent of a prop that was made with the pitch you want. It is far better to trade in, or sell, a prop and just get the pitch you want. Re-pitching is best when the pitch you need is not actually offered form a manufacturer, the change is only an inch or so or other blade modifications are desired.

---

I should add that I did not realize the WOT RPM range for the 75 is only 4800-5200 RPM. Thank you Tim for pointing that out.

That is a very important part of the equation and why it is so important to always cite the WOT RPM range of your motor when asking for propeller recommendations.

That also, partially, explains why a 75 HP Mercury two stroke could be turning so tall a prop relative to a Mercury 90 two stroke on the same hull; it does not have to turn it as high.

---

Hey Tom,

I tried to look for my test results with the Stilleto at 17p but I can not locate them. If memory serves me correctly at 17p I had 36mph at 5400 RPM WOT. I wanted to raise the pitch to lower the rpm and possibly gain some speed.

I tried to return the 17 for a 19 but the vendor I bought the prop from wanted $150.00 to return the old and send out the new one. A guy in my fishing club owns a prop shop and he convinced me to have him repitch the 17 for half that price. It actually worked out quite well for me but as you said it would have been better to be able to swap for the correct size from the manufacturer.