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ContinuousWave: Whaler Performance
Propeller: STRIPER 15 with 70-HP
|Author||Topic: Propeller: STRIPER 15 with 70-HP|
posted 07-29-2004 01:25 PM ET (US)
1981 STRIPER 15
I'm achieving speeds in the mid 30-MPH range measured by GPS
What should I expect from this set-up? I read from earlier post speeds in the lower/mid 40-MPH range would be typical. What props are being used to attain these speeds?
posted 07-29-2004 01:56 PM ET (US)
I have a 1982 STRIPER 15 with a 1993 50-HP Yamaha. I hit the mid-thirties with the stock aluminum prop. You should be getting in the lower to mid forties.
Tightlines & Happy Whalin'
posted 07-29-2004 02:18 PM ET (US)
I have a Dauntless 15 with a 75-HP Evinrude FICHT motor. The recommended prop for that is a 13x15. I get 42-MPH at WOT with a Stiletto SS performance prop.
Your motor may not be able to push a 19 pitch prop. That sounds a little steep to me, but I'm not a prop expert.
posted 07-29-2004 02:51 PM ET (US)
The typical prop for a 15 with a 70 HP outboard, not considering skiing loads or other non-typical performance requirements, is the 13x19.
With this prop and a strong and healthy engine, you should expect to see lower to middle 40's for speed. I have a 1986 Striper with a 1989 Johnson 70
posted 07-29-2004 03:14 PM ET (US)
1989 GLS 15
1995 70 HP Evinrude
Michigan Wheel Aluminum Vortex 19-inch Pitch
43 MPH on GPS
posted 07-29-2004 04:43 PM ET (US)
I have a like new 13x19 SST that came with our 70 Evinrude that we use on a Striper 15. We took it off and put on a 13x17 since we mainly ski.
The 13x19 is probably preferable for general cruising unless you load the boat heavily.
posted 07-29-2004 06:23 PM ET (US)
Now I guess it is time to check some things out on the engine. I'll need a tach to check engine speed, and check the timing. Already check carbs to see if opening all the way. Ok here. Plus sychronized the three. "Fixin' to" pull plugs to see how they are burning.
I'm beginning to wonder if this is a fly-wheel hp rated moter instead on the prop rated new versions like most here are running. Anybody running a early 80's model?
Anyway, thanks for the suggestions.
posted 07-29-2004 09:27 PM ET (US)
Well....I checked the plugs and all are burning evenly and no carbon build up. Also checked the compression....all between 145 - 150 psi. Now I guess I'll check the timing and get the rpm's at WOT. This motor runs smooth as silk...hard to believe something could be wrong with it..hopefully 40+ is in the near future!
posted 07-30-2004 01:32 PM ET (US)
Unless you know how to do timing....leave it alone. Check to see if timing is opening up all the way but don't mess with it. Worse case scenerio is set it to factory specs. I have NEVER seen the timing go out on an outboard but have seen MANY people mess it up and detonate a perfectly good engine. How high is ypur engine mounted and what RPM is most important. PTnT is necessary to get that hing hoofing,. if not trimmed to the hilt, she will only do high 30's probably. You redline at 5500.
posted 07-30-2004 05:32 PM ET (US)
Bigshot is right about that...the motor must be trimmed out to the max to achieve 43 MPH, and it's shooting a pretty good roostertail of whitewater at that speed; not much boat in the water.
The motor is trimmed pretty far out in this photo - we're running around 40 MPH after just shooting out of the hole.
posted 07-30-2004 05:47 PM ET (US)
Buckda, Great shot...really airing it out!
Bigshot, Motor has T&T and the cavitation plate is dead even with the bottom of the boat with motor trimmed all the way down...front portion may be a little higher that the bottom. I've been reading up on the timing and you are right on the money. It looks like max advance is 19 degrees. Timing is checked at approx 4700 rms with a strobe light. Dealer has a tank with hub hook-up and charges $65. I'm about at my witts end on this one.
posted 07-31-2004 10:55 AM ET (US)
I don't see where you have checked WOT rpm's, what are you getting in the water vs a test tank?
posted 07-31-2004 11:19 AM ET (US)
For information on horsepower ratings, see my article in the Reference Section:
[Edited thread for clarity.]
posted 07-31-2004 11:20 AM ET (US)
Discussion of engine performance and propeller evaluation is not of much value without readings of engine speed from an accurate tachometer.
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