WOT RPM Too Low - major issue? cause?

[artg]

Rev up...cut out....in neutral could be ecm controlled. This would make since to protect the engine.

If everything is running good and no sputters or misses, check your throttle cable. You could have extra slack in the cable.

HMB - thanks for your inputs!

I'm currently far away from the boat, but before I left I was able to try WOT a few more times in different conditions, and took a peek at the spark plug wires.

I noticed upon closer inspection that the Perfect Pass RPMs (digital) were 100-200 less than analog tach depending on the day/speed (see pics), and when I was alone in the boat the last time I was able to get it up to 4600 (digital)/4800 (analog) and 40.4 MPH. Also just realized that the Speeds aren't matching - GPS PP is 40.4 when boat says 42. Both tachs run off the same signal, so not sure why they'd be that far off or which to trust as more definitive...? My wakeplate was all the way down (nose down), not sure if that should have been be as high up as possible to minimize load?... After researching I've seen at least one account (at lower speeds in the 30's) where wakeplate all the way down vs. up was a 2-2.5mph difference. Assuming that's mph and a corresponding RPM difference, seems possible I get a healthy RPM and speed at WOT after raising wakeplate... I normally have wakeplate down so I didn't think about it at first...

The spark wires I looked at were corroded (see pic) and flame arrestor had gunk and needs to be cleaned. So I'm planning to start with the easy stuff (hopefully easy) as part of my winterization this year -> replace Spark Plugs, Spark Plug wires, Distributor Cap and Rotor, Fuel Filter (there's just one not two right?), PCV Valve along with Oil Filter, Engine Oil, V Drive Fluid, Transmission Fluid as part of winterization. I'm planning to do those as the last thing before I pull her out of the water so I can hopefully take it for a spin afterwards and see if anything got better

If I have the time and energy I'll try to test fuel pressure and compression test the engine as well.

I'm amassing all the parts/materials and will plan to report back in a few weeks after I've had a chance to work on it.

unnamed.jpg

image_50384385.jpg

image_67237377.jpg

[Holdmybeer]

Are you on a river or lake?
Speed from a paddlewheel on a river will compensate for current and give a higher speed depending on traveling up stream or downstream. It would explain speed difference between analog and GPS.

If the rpm input is coming from the same source and the gauge is different than the PP I would assume the gauge may need calibrated and the analog runout from being 15yrs old is what you are seeing. Moisture and age plays havoc on analog electronics.

The plug wires are not horrible, I have seen worse. But doing all the routine maintenance stuff to make sure is just good practice if you don't know the condition from previous owner. Only 1 fuel filter I know of. Primary filter is usually part of the sending unit in the tank and doesn't require changing. Just the metal canister on the backside of the engine.

The drag from the wake plate will out a small load on the boat. If you can get smooth water after all your work try wake plate up once you are moving and you should pickup some speed. Good to see it is running well just not seeing what you expect.

[artg]

Are you on a river or lake?
Speed from a paddlewheel on a river will compensate for current and give a higher speed depending on traveling up stream or downstream. It would explain speed difference between analog and GPS.

If the rpm input is coming from the same source and the gauge is different than the PP I would assume the gauge may need calibrated and the analog runout from being 15yrs old is what you are seeing. Moisture and age plays havoc on analog electronics.

The plug wires are not horrible, I have seen worse. But doing all the routine maintenance stuff to make sure is just good practice if you don't know the condition from previous owner. Only 1 fuel filter I know of. Primary filter is usually part of the sending unit in the tank and doesn't require changing. Just the metal canister on the backside of the engine.

The drag from the wake plate will out a small load on the boat. If you can get smooth water after all your work try wake plate up once you are moving and you should pickup some speed. Good to see it is running well just not seeing what you expect.

Lake. Forgot to consider the current factor. Speedo has a calibration knob, but not rpm right... I do actually have a spare tach guage maybe I'll pop that in at some point to compare.

[2in2out]

Don’t you have to adjust the frequency on Perfect Pass for the tach freq? I thought this came up in a previous discussion about one of the GPS systems.


2022 SA 450

[Holdmybeer]

Don’t you have to adjust the frequency on Perfect Pass for the tach freq? I thought this came up in a previous discussion about one of the GPS systems.


2022 SA 450

I remember reading that elsewhere also. Something about 10,000 vs 15,000.

[2in2out]

Is it adjusting to the transmission ratio? I think Sonic may have talked about it, or someone who did their own surf system had to make that adjustment on the pulse rate for RPM.

I could be completely off base, but if Holdmybeer remembers it too, that makes us both liars.


2022 SA 450

[artg]

Is it adjusting to the transmission ratio? I think Sonic may have talked about it, or someone who did their own surf system had to make that adjustment on the pulse rate for RPM.

I could be completely off base, but if Holdmybeer remembers it too, that makes us both liars.


2022 SA 450

hmmm - tach should be standard with the only question being how many cylinders just like all tach gauges right? it’s straight engine rpm so not sure what transmission ratio would have to do w it? mine is drive by wire as well. I don’t see any such setting/calibration in the manual.

I did reach out to perfect pass about the pp display vs analog display so if calibration/setting is needed i expect they’ll point me to it. they’ve been super helpful in the past.


Sent from my iPhone using Tapatalk

[Holdmybeer]

Is it adjusting to the transmission ratio? I think Sonic may have talked about it, or someone who did their own surf system had to make that adjustment on the pulse rate for RPM.

I could be completely off base, but if Holdmybeer remembers it too, that makes us both liars.


2022 SA 450

Proof we aren't both crazy. Not sure if it applies here but this could explain why speed is off not RPM.

https://forum.moomba.com/showthread....ighlight=Pulse

[artg]

Proof we aren't both crazy. Not sure if it applies here but this could explain why speed is off not RPM.

https://forum.moomba.com/showthread....ighlight=Pulse

Not crazy!!! But this was a diy/homebrew version of perfect pass, not needed for the real thing
Or to put it another way, believe pp display would already be calibrated from the factory to the gps signal it comes paired with. This appears to apply only to his speedo, not the rpm. Rpm signal is standard - can plug and play tach gauges and only setting change would be for how many cylinders.

Sent from my iPhone using Tapatalk

[Holdmybeer]

Correct. You have the real thing. I didn't think this applied.

Thinking more, have you ever checked your speed with a phone app. Use the app to compare the other 2. If PP and the GPS on your phone match then the gauge is off for speed. If phone and gauge then PP is off.

RPM being off is still confusing if they are the same signal. But PP focuses on maintaining speed and doesnt really care about RPM. Correct?

At these 40+ mph test do you have throttle left or is WOT maxed out?