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Author Topic:   12.75x21 prop 1999 Outrage 17
Dan posted 04-30-2001 10:04 AM ET (US)   Profile for Dan   Send Email to Dan  
Does this sound right: 12.75x21 prop 1999 Outrage 17 with 1999 115 Merc 2 stroke?

I don't know if my tach is 100% accurate. At WOT it read close to 5600 and the speedo read over 42mph -- I immediately backed off because WOT is supposed to be 5000-5250 max.

I spoke to a Merc dealer and I can bring the boat over for a bay test. The testing cost $85. They have new model stainless props that they'll sell for $100 below list. If I need to bring down the RPM's I would be going to a 13x22. They said they might have an older style new prop for less money, but I heard the new styles have better safety feature hubs in case you hit something.

Other question: Do engines idle higher when out of water during fresh water flushing?

Tom W Clark posted 04-30-2001 08:48 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

I'm not the Merc expert but a 21" prop already seems tall. What I don't understand is the 12.75" diameter. Usually there is an inverse relationship between diameter and pitch in a given manufacturers line of props. You say the bigger prop is 13" x 22" which is bigger pitch and diameter. Is the prop you have on there one which has been worked on by a prop shop? If so then there might be some blade surface area that has been removed which would account for both the smaller diameter and the engine over reving.

To answer your second question, no, your engine should idle at the same speed out of water as in.

lhg posted 04-30-2001 09:11 PM ET (US)     Profile for lhg    
Dan - In checking the Mercury propeller charts for your engine, it appears you are running Mercury's standard 3 blade aluminium prop. They show weight range of 1400-2300lbs and speed range of 40-47.

For a boat in this speed range, you definitely do not want an aluminium prop.
You should get a stainless Merc performance prop, either a 3 blade Laser II or a 5 blade High Five. I'd go with the Laser. It is shown as 13 1/2" dia and 22" pitch, weight range 1100-1800 and speed range 43-49mph. This should bring your RPM's down. Tom is generally right about the larger diameter, but in this case it is because of a change to whole different family of props.

It also seems that your boat wouldn't run this high of a pitch, but maybe the Merc 115 is a strong engine. With a Laser installed, the engine should be lifted one or two bolt holes up. You will like that prop. Agressive hold-on and good bow lift. The 17 will fly!

If you don't want to spend the money for an SS prop, your only other choice would be to go for the 23" pitch aluminum.

Clark Roberts posted 05-01-2001 05:13 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Dan, not to conflict with Tom, but an engine's idle should be adjusted in the water and in gear! And the idle speed will be a couple hundred rpm higher out of the water (on the hose) due to the lack of a head of water in the engine's midsection.. exhaust is less restricted... etc.. Clark.. Spruce Creek Navy
Dan posted 05-10-2001 08:34 PM ET (US)     Profile for Dan  Send Email to Dan     
Update: I test drove my 1999 Outrage 17 today in calm water, full tank of gas, myself and a closed sun top. 1999 Merc 115 25 shaft with aluminum prop 12.75x21. With engine warmed up, and test repeated 3 times, at WOT tach read 5200 and speed measured 45mph. What are your recommendations for a stainless prop. I'd like to get out of the hole faster. I want one of the new style Merc props with the plastic hub and a spare plastic hub.

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