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View Full Version : Mercury 2001 90 hp. Prop suggestions



Tooz
11-07-2015, 12:34 PM
I recently purchased a 2001 90 hp. Mercury four stroke,which is on a 17ft. aluminum Tracker deep-vee fishing boat. It came with a stainless prop and I am looking to purchase an aluminum prop. Any suggestions on size, pitch? Thanks Tooz

galamb
11-07-2015, 10:26 PM
Nobody can really answer your question without a few more details.

Likewise, you can't look up on "some chart" and see what prop to use.

Even two identical 17' Trackers, both powered with a 2001 90 horse 4S may use drastically different props.

When selecting a prop you pick one that will allow the motor to get into it's Wide Open Throttle Range (WOT range which is 5000-6000 for this model, so lot's to play with), when you run at full throttle.

If you "run heavy" then you need a prop with less pitch than if you "run light".

The only sure way to pick a prop is run your boat "as you typically will" (eg. 3 passengers, half tank of gas, extra battery for the trolling motor etc) and see what rpm's the motor is making.

If it's running in the wot range then you have the correct pitch. If the motor will not reach the wot range then you select less pitch, or less diameter or both. So say you can only make 4800 rpms. In that case if you selected a prop with 1" of less pitch that should raise the rpm to 5000 (just barely inside your range).

On motors with a large range (1000 rpms for this model) you typically shoot for the "middle" or slightly over - so your target might be 5500-5600 rpms.

RPM's will "change" due to weather conditions (when it's hot/humid rpm's fall - cool/dry they rise), so if you shoot for the middle you will have some room to account for natural fluctuations.

Then you have other considerations. All else being equal your current stainless prop will not make the same rpm's as an aluminum prop of exactly the same specs. Why? Stainless "flexes" less than aluminum, so it "bites the water" harder and the motor works (minimally) harder to turn the stainless prop - maybe not enough to notice, but there will be a difference.

Also you have (commonly) 3 or 4 blade options. If you want a "better hole shot", to pop up a skier or wake board then you select a 4 blade (at the expense of some top end speed) - if speed is all you care about, then you go with 3 blade.

So for all my babbling, the answer to your original question is - sorry, we can't even begin to tell you what prop you should buy.

Tooz
11-08-2015, 03:44 PM
Thanks for your reply. You didn't babble, you provided some excellent incite to a prop search.