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Author Topic:   Prop for 15-Sport For Water Skiing
stillwater posted 06-03-2004 11:38 AM ET (US)   Profile for stillwater   Send Email to stillwater  
I have 1987 15' Sport with 2001 Johnson 70hp. Original alum prop is on motor and seems to work well except when pulling a skier. It is very difficult to pull an average adult up with out a long struggle. I had a 1980 Sport with a 70 Mercury and it easily pulled up a skier even on one ski. Can anyone recommend a good prop for skiing?
Mike
jimh posted 06-03-2004 09:06 PM ET (US)     Profile for jimh  Send Email to jimh     
You probably will want to get a propeller with lower pitch and possibly more blades to get better results in pulling someone on water-skis.

Making analysis of the propeller is greatly aided if you know the current propeller's dimensions and the engine's crankshaft speed at wide-open-throttle.

Buckda posted 06-02-2004 06:57 PM ET (US)     Profile for Buckda  Send Email to Buckda     
My 1989 Sport with 70 HP evinrude will pull any skier (well, almost any) with my "spare" prop - at 15" pitch. Be careful though, as you can "over-rev" the engine with that low pitch.
When not towing a skier, the holeshot is very fast, as in, almost non-existent.

Dave

Cicada posted 06-02-2004 11:21 PM ET (US)     Profile for Cicada  Send Email to Cicada     
I agree with the 15" pitch. I forget the diameter right now.

Have a 1978 Sport with a 1978 70hp Johnson. Maximum rpm for that motor is 5500. With the 15" pitch it would push it to a tad over 6000 rpm. We used the prop primarily as a spare and for wakeboarding. Kept the rpms under 5500 when the prop was on otherwise.

Yes the hole shot is quick. Especially when you add plutonium and garlic to the two cycle oil.

Paul

jimh posted 06-03-2004 09:18 PM ET (US)     Profile for jimh  Send Email to jimh     
It is also important to know the lower unit's gear ratio.
where2 posted 06-07-2004 12:41 PM ET (US)     Profile for where2  Send Email to where2     
Considering I run a 17" aluminum for skiing with my 1985 70Hp Johnson, and considering the description of the effort required to pull up an "average adult", I would suggest going to the next lower pitch whatever that may be.

Your description sounds the same as I would describe the problem with the 19" SS on my 15' Sport with a 70hp engine. I can load 4 people in the boat and still get up on plane with no problem, but drop an average adult on a Slalom behind the boat and even with 2 people in the boat it is more trouble than it should be. The 17" pitch does the trick for me, but as others have said watch the revs...

I'm still searching for an all purpose prop with the best of both worlds... At the moment, I still don't own it. However, I really would like to test a 4 blade composite with adjustable pitch blades...

stillwater posted 06-08-2004 05:17 PM ET (US)     Profile for stillwater  Send Email to stillwater     
thanks for the tips. I am going to try a 13 1/2 X 17 Ballistic stainless next week, so I'll post the results as well as the size of the oe alum prop.
Peter posted 06-08-2004 07:14 PM ET (US)     Profile for Peter  Send Email to Peter     
The OMC 3 cylinder loop charged 70 uses 2.42:1 gear ratio. The 3 cylinder "looper" (a nearly bullet proof engine) never had much low end torque which is the reason it used such a high gear ratio. A 17 inch pitch prop should work for skiing, while the 19 inch is ideal for speed lightly loaded.

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