Perfect pass on indmar 351

[Dano]

Anybody using PP 9.2 with a carbed indmar 351? I thought mine was locking and settling into speed well, but after driving several other boats I have noticed they hit target speed and settle without overshooting at all. It’s a very sudden change in acceleration after PP beeps. Mine does not get this and runs past set speed 1-1,5mph. Settling back to set speed a few second later. I’m trying to sort out if it’s just the way it is on these Holley carbed motors or if something is not right with PP. I have Kx set at ++ and I have tried a stronger return spring with no change to how it settles to target speed. Runs good ball times after it’s settled and the pull feels very good. It’s just the settling into target speed.

[VermontSkier]

@Dano I run the newest PP 9.2 on my 2002 Malibu Sportster which is a carbed indmar 351. My boat maybe overshoots slightly but very quickly settles in. When I accelerate pulling a skier the PP head unit beeps as it locks into the RPM and then GPS takes control. I assume you have done auto-calibration? In comparison, my ski partner has a 2006 response that is DBW and fuel injected and that boat locks in perfectly so maybe it has to do with having mechanical throttle on our boats as well as the Carbs.

[Dano]

@VermontSkier yes I’ve done auto calibration. Mine beeps as it should but doesn’t seem to react right away. Not really a noticeable change in rpms or acceleration. I’m comparing to another boat that I’m familiar with that is the same hull but running the mercruiser tournament ski 350 with a 2 barrel carb. In that boat pp beeps and the boat almost immediately stops accelerating and locks onto the set speed. It’s very noticeable change in acceleration once pp beeps. Same with several other boats I ski on but they are DBW.

[BraceMaker]

mind taking a quick video? engine off key on. Video your linkage from neutral to full throttle and back. Then go full throttle turn off the key and loosen the servo cable with the black knob.

[Dano]

@BraceMaker will do when I get back to my boat Sunday. I have done this test when I installed and both servo cable and throttle cable moved freely and smoothly. I will double check though.

[BraceMaker]

looking for 2 things one is smooth but another is if the angle of the control cable jerks about. sometimes engine hatch will also flex the PP cable.

[skiboyny]

Try to add a return spring, see if that tightens it up.

[Dano]

@skiboyny I tried a stronger return spring. no difference.

[On_edge]

What is the status of your secondaries, still vacuum operated? Remember PerfectPass can only control the primaries, normally you do not need the secondaries for pulling slalom and can be disconnected from the bellows, once opened even a little they are somewhat slow to close.

[Dano]

@On_edge i do have vacuum secondaries. That would explain the behaviour I’m seeing. I’ll have to check into this further.

[ReallyGottaSki]

Good for a test, but Consider the vacuum secondaries close mechanically and instantly. But yes likely confounded by the nonlinearity of the Holley response

[Mastercrafter]

Here's a question I've not seen an answer to yet. Has anyone run PP on a Holley Sniper EFI converted boat? I'm told those systems have great throttle response compared to a carb, and I wonder if it would really make PP come alive, maybe feel more like ZO?

 

[ReallyGottaSki]

Having done so I believe the best way to wake the venerable 240hp 351 up is better heads and a little more cam and an intake. I believe the fuel mix method is less important than the rest of the engine. Same carb now, but is a midrange monster, very sensitive to minute inputs, where it was soggy to inputs before. cannot pull it down. it will do 42 mph on just the primaries now, 1 mph faster than all four open before.

[jpattigr]

I had the 240hp PCM in my 97 SN, I swapped out to GT40 heads, Edelbrock intake, rebuilt the carb and it was a huge jump in performance. The boat was way stronger in all areas.

[Dano]

@jpattigr those are all good mods and I think they would help with throttle response, if I had time and money I'd likely do the same. I did upgrade the prop to an OJ CNC 13x11.5 which was such a big improvement It really has made the want for more power non existent. I haven't had a chance to mess with things since my original post. I did talk with PP and they told me if everything looks to be set up correctly it's possible the motor simply doesn't react as quickly as others to decelerate. It is lower compression and lower HP, perhaps the vacuum secondaries play a roll etc.... So his suggestion is to run auto cal again to see if it calibrates differently. if not, then manually lower the base line RPM for each speed so that PP will lock onto the RPM earlier and not run past set speed. PP sets a temp RPM for the set speed on each pass as it gets GPS readings after it beeps when throttling up. So changing the baseline RPM should not effect set speed or ball times. As it is right now once PP beeps and settles to set speed it does a very good job of maintaining speed, i get good individual ball times and overall. I just want it to settle to the set speed a little faster. Other peoples boats do, so I want mine to as well. I do not think this is a PP issue so much as it's new tech on an old boat.

 

[ReallyGottaSki]

Oh, 11.5 pitch means your deep into the primaries where the gets little dull to inputs. This means conversely, the pp starts pulling back things don't happen instantly.

It may just be your specific combination at the moment

 

[On_edge]

Typically the linkage between the primaries and vacuum secondaries is a sliding rod in a slot, at idle the secondaries are forced to close when the primaries fully close. Otherwise the secondaries are controlled by the air flow through the primaries and some sensing the air flow to the secondaries, to add complication there is also a check valve and bleed port. Thus when PP wants less throttle the vacuum secondaries do not close in lock step with the primaries.

[Dano]

I took the boat out today and messed around with it a little. Ran it through auto cal then confirmed it was still running past set speed. manually lowered baseline RPM for each speed by 40rpm. This definitely helped it settle into set speed quicker. I think 40rpm may have been a little too much. I made several no skier passes through the course and both timed out perfect. Thats starting from a short set up and throttling up hard. boat was settled nicely before the 55's. I say 40rpm may have been too much because the wind came up and the water got a little lumpy, the tail wind resulted in best results but head wind saw the boat hit set speed and fall slightly below before PP brought it back up. But that was all much quicker than the original Autocal settings.

 

to be fair to perfect pass autocal may work pretty good in more controlled environment. i'm on a large public lake that nearly always has wind even when it seems calm. I've run several autocal's and it kicks out different baseline RPMS depending on the day. For instance today autocal headed north consistently set 34.2 baseline RPM at 3420 but turn the boat around and head south and the baseline would set at 3370 consistently. This was at a time when the wind was very light if any. So perhaps big lakes have stonger currents than I thought. 50rpm difference seems like a lot.

 

 

[BraceMaker]

@On_edge wonder if it would be workable to slip a small screw and nut through the slot on the secondary shaft so as to push the secondaries shut.

 

install the heaviest spring on the vacuum diagram, screw in the slot to close it down sooner. might require some sort of spring relief om the rod.

 

could be worth it if the concern is the boat not shutting down digitally enough for stargazer.

[BraceMaker]

Or even a small bit of weed eater fuel line.

 

 

[On_edge]

Normally if the little circlip is removed ( don’t loose it ) and the rod connected to the vacuum diaphragm is slipped off of the secondary bell crank the spring and off center butterflies will keep the secondaries constantly closed.

[Dano]

For anybody following this thread. I'm on public water that is really hard to get good water this time of year. The tweaking I've done isn't honed to perfection. I have too many variables with wind and boat wakes etc.... But the changes have resulted in a much faster lock to set speed. If you are running a carbed boat with a 4 barrell and you find the boat runs past set speed, and takes several seconds to adjust back down. Try this. Run auto cal to get your baseline RPM's established, enter the baseline RPM screen and lower the set speed RPM by 30rpm for each speed. You should now find that the boat settles into set speed a little faster. If you find it is now settling in below set speed and then adjusting up, simply go back to baseline RPM screen and add some RPM's. Maybe it's just my particular set up. but This does seem to have resolved my concerns.