Reply With QuoteYOU MUST BE PUTTING IN INCORRECT INFO BECAUSE IT DOES WORK. I'VE USED IT PLENTY OF TIMES,AND IT'S BEEN ACCURATE.
Interesting tool. According to them, I would need a negative prop slip. My theoretical top speed is 105 (based off of pitch), but that calculator comes up with 111. Yea, right.
YOU MUST BE PUTTING IN INCORRECT INFO BECAUSE IT DOES WORK. I'VE USED IT PLENTY OF TIMES,AND IT'S BEEN ACCURATE.
i just added that site to my favorites. very interesting to kick around numbers while contemplating my next prop purchase.thanks for posting that link!
260 STINGER:
YOU MUST BE PUTTING IN INCORRECT INFO BECAUSE IT DOES WORK. I'VE USED IT PLENTY OF TIMES,AND IT'S BEEN ACCURATE. You're right. I entered the wrong boat weight...hmmmm....now where can I loose 1,000 pounds?
Just thought I would post some numbers from my last test & shake down on Saturday the 25th, 2003
I went from a 1:63 & an SS 4 blade 15 ¼ X 27 to a 1:42 final & had the prop reworked & taken to a final adjustment of 15 ¼ X 26 with a bit more cupping.
The outcome of this round of testing is
3000 RPM 45 & 13.49 % prop slip
3500 RPM 55 & 9.37 % prop slip
4000 RPM 65 & 6.28 % prop slip
These MPH are from GPS and rounded down to the nearest MPH
I just got back into the water after 2 months dealing with INS & surveyor & being in the shop getting fixed (wife hit a submerged object). The shop resealed the transom & did a teardown & inspection of the upper gear case. My wife was with me so I didnt want to push her safety zone since she was the reason it was being repaired. Sometime later I will see how far I can turn the motor when I get seat time to myself.
This aint no custom built ride but the numbers sure surprised me & I have to say thanks to Steve at Keystone Prop Service in Sand Springs, OK for doing some good work to my prop.
Originally posted by Essex502
6% does seem to be very low. Other figures I have heard are always higher. It leads me to believe maybe the tach isn't accurate. I wonder what would be a good way to test that?
Maybe if you have one of those Antique things called a Dwell Tach you could possibly find a way to check it. It would take two people though, with the engine hatch at least a little bit open. Maybe you could hook the dwell tach up with extention alegator clips or something, don't know if that would effect the readings...just thinking out loud...
Also with the dwell tach being pretty much obsolete if you have one, hard to tell if it is calibrated properly... something to think about anyway.
Originally posted by Essex502
Thanks! I'll have to look into it. I wonder if the Gaffrig Tachs can be calibrated?
I am reasonably sure that the software and cable are proprietary merc issue and only dealers are supposed to have them. I had the dealer try to synchronize the throttles for both engines in my offshore boat using the throttle position sensors... I asked him if I could get the cable and software. After a 15 minute lecture on why I shouldn't want it because I was still under warranty, he said that it would not matter because it was only provided to dealers...I don't know if he was being straight up or not...
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