Perfect Pass Drift?

[ESPNSkier]

Has anyone ever experienced speed drift on older (2004) Perfect Pass systems? I have been skiing 32 mph this summer/fall and was running 28 off maybe 50% of the time. I took almost a month off due to travel and over the last 3 or 4 sets I am struggling with 22 off again....how did I lose an entire pass in one month? Yesterday I pulled out the GPS and checked my 32.3 mph pass....only to find out that it was actually 33.7 mph. The setting has not changed (32.3 mph/3025 RPM) which was dead on the last time I checked with the GPS mid-summer. I have not changed props or anything else other than the alternator. Could this impact PP? Oh well, it was time to work back up to 34 anyway!

[Alberto Soares]

I imagine some problem with the GPS antenna, anyway, when skiing with PP Stargazer I always use RPM mode, got tired of getting bad times.

[Gloersen]

@ESPNSkier

 

Check skier weight/crew weight?

 

The 33.7 is based on end course times?

 

PPC or PPSG?

 

Also 3025 seems low (though that would yield slow times) for 32.3 baseline RPM, but depends on the prop, etc.

 

Sometimes a prior heavy crew weight entry gets overlooked. You may have ~ 150 lbs too much.

[ESPNSkier]

PPC with accurate skier/crew weight. Speed based on straight line GPS readings outside of the course.

[bigskieridaho]

@ESPNSkier I have found if the crew weight is not entered correct it drastically changes the pull and speed. Either way PP tends to surge or have a different pull either way. Are you running SG or standard NG? Z box or not?

[ESPNSkier]

Yes, weights entered correctly. BTW: This is an older 2004ish PP without all the new bells and whistles. Version 6.0 if I remember correctly.

[ESPNSkier]

1993 MC ProStar with carbureted 250 hp Indmar Ford.

[BRY]

@espnman A couple things seem odd.

 

33.7 mph from 3025rpm does not sound right. Most older boats with 1:1 ran a 13x13 and 32 was ~3200, 34 was ~3400 and so forth. Boats with reduction gears ran bigger props and higher RPM. What boat/prop do you have? Sure your getting 33.7 from 3025?

 

PP Classic is rpm based, has no idea about speed. The "MPH" in PPC are just labels assigned to a group of settings. Key are SSD, Baseline RPM, Wind Adjust, Crew Weight, Skier Weight, Kx and Px (switch). PPC also needs magnets. Not just for timing but to trigger SSD but seemed to chase time as well as RPM (seemed to give hot segments after slow segments). Setting baselines out of course, no magnets so no SSD, seems you are setting for a "out of course situation". Go "in course" with magnets and SSD comes into play and different result (speed). Checking out of course may be root of speed issue, just a theory, been a long time since I have run PPC. Used to be quite good at it.

As far as your skiing perhaps the month off so rusty plus water temp change was enough for this issue to bite you. You just managed it in summer.

So, dumping everything else, what times are you getting in course for 1 ball, 3 ball, and end time? ABT is best but those three can illuminate whats going on.

When I was in WA State in spring we would take boats from the Western side to the Eastern side chasing heat. Left 50ish water for 80ish water. Temp and mineral content difference between the lakes necessitated we reset baselines. Drop boat in and go reset. Same before tournaments then, checked and set every boat every speed baselines, in course with ABT.

 

[bigskieridaho]

I still have the old style 6.5ng as well. Have to use magnets, and all setting have to be accurate for initial setup. Mine you actually have to run 34 to run 32mph, and 36 to run 34mph. Unfortunately the old style PP systems will never be that accurate, but you just have to keep dialing them to get the correct settings. May be time to upgrade to SG with a Zbox!

[DW]

@ESPNSkier : a bit of a flyer but you mentioned alternator change. Perhaps the RPM signal strength has changed to alter the calibration a bit due to voltage level change with new alternator. Given you comment on skiing a course, checking times may need to be monitored.

[ESPNSkier]

Thanks all, good advice and I need to check a few things. But first, yes these are old baselines that I set a few years ago when my course had magnets and I was getting good times at both 32 and 34 (when I remembered to enter weights correctly). Of course, I did not write these settings down so it is quite possible that the RPM settings have somehow changed and my speed may in fact be slower. Although I do occasionally ski behind a 2016 SN 200 with ZO and the speed feels the same to me so I don't think it's off by much. My course no longer has magnets and I have not put a stop watch to it in a long time. I'll likely need to put magnets back out and then reset my baselines. And yes, @BRY, it probably was the time off of the water coupled with cooler temps. Thanks all and Happy Thanksgiving!

[Alberto Soares]

Use a chronometer to set the RPM baseline, preferably pulling a skier, thats the way I always did with my PP boats

[LeonL]

Bottom line is this --- the only way to get accurate speeds / baselines with PPC is to time it in the course. Otherwise you're just chasing your tail. Stop watch skills are also questionable. At least put a magnet on each end and take out variables.

[Alberto Soares]

if you use magnets be sure to put all of them with the correct pole in the same direction (up/down) and the timer in the right position (forward/back), otherwise you will get bad times

[ESPNSkier]

So, never mind my earlier post! Checked it again tonight and 32.3 mph is actually 3210 RPM and I got times within tolerances by hand timing....good enough for now until I can get magnets back in. I don't know where the 3025 RPM came from. And yes, I checked the GPS without a skier and it was 33.7 mph which does apparently equate to 32.3 with a skier in the course. On the plus side I did finally run 28 off again at 32 mph with good times.