Prop for new Suzuki 90

Plan C · Posted: Tue May 13, 2025 5:55 pm Post subject: Prop for new Suzuki 90

I’m just back from the wonderful gathering at Friday Harbor. What a fine community, and grateful for being a part of it.
I noticed that many of us have Suzuki 90s on vintage 22 footers. I should’ve raised the question of props. When I hung the new motor, the prop is a 3x14x17, aluminum. I think it is fine, and gets me up to 5500. I’m just curious what others have, as I am about to buy a spare. For some reason, there is no discussion of this on the forum for newer Suzuki’s. I think this will be a general interest.

thataway · Posted: Tue May 13, 2025 6:29 pm Post subject:

What prop do you have now, (metal, pitch, and diameter, and any "model"). What is your boat speed at 5500 RPM?

What speed and RPM are you cruising at now? The rated range for WOT is 5300 to 6300 (when the rev limiter kicks in). The Suzuki 90 tends to be a "strong motor"--at or above its rated HP. A SS prop is better than an aluminum prop. But if you tend to run into bottom items, stick with the aluminum.

I often purchased my "spare prop" for 3500 foot elevation, and in the 22, I had a prop for 3500 and 7,000 feet, (Lake Powell and Yellowstone). Sea Level was the standard SS prop.

Also how loaded the boat is, is important. Are you going with only 2 people and no gear. We would be at Lake Powell with full fuel, full tank and 14 gallons extra of water, a 2000 watt Honda generator, food for a month and at times both a freezer and refer. That with gear dinghy, kicker and electric dinghy motor adding up to over 1000 lbs. (also up to 3 dogs).

shad · Posted: Tue May 13, 2025 9:25 pm Post subject:

I have an older Evinrude 90HP and just went through several props before landing on one that worked. My boat came WAY over-propped with a 19 pitch that could barely hit 3600 RPMs out of an optimal 5000-5500 RPM range. After testing 3 and 4-blade 15p, I ended up with an aluminum Solas 4-blade 13 pitch prop that lands in the correct RPM zone. The prop "sings" at a lower RPM range, but I am hoping the singing will wear it self out at some point. The prop sing freaked me out until I understood it was just a resonance issue. Filing the prop edges can supposedly fix it, or water grit should eventually do the job.

Looking up the Suzuki DF90A, it appears to have a gear ratio of 2.59. Assuming a top speed of around 30mph, a 15 pitch prop might be about right. Your current 5500 RPMs with the 17p is on the lower end but is still in range. Each inch will get you an extra 200 RPMs or so, so a 15 pitch should get you around 6000 RPMs.

The online prop pitch calculators can help you get in the ballpark relative to the prop that you already have RPM and speed stats on.

https://www.omnicalculator.com/physics/prop-pitch

It's not an exact science with all the variables involved. Hopefully someone with the same motor, boat, and approx weight can chime in with their prop specs.

(Take my advice with a grain of salt, as I'm a newbie relaying my experience sorting out the right prop for my motor...)

Plan C · Posted: Wed May 14, 2025 11:46 am Post subject:

My 3x14x17 gets up to 5800, so I’m okay with it. What I’m asking is to see what props others are using with this engine on traditional vintage 22’s.
If the Friday harbor gathering was a representative sampling, it appears that the engine of choice to replace original engines is the Suzuki 90. I have now had two of these engines, and can attest to their quality and durability. They are excellent.
What props are on these other 90’s?