One owner of a supercharged FX SVHO describes a ski that runs at about 7500 rpm and then, after 20 to 30 minutes, falls to 4500 or 5000 rpm without any alarm. There is no beep and no light. The cause in that case is unknown, and there is no point pretending otherwise. What can be said is how to go about catching it, because a problem that needs half an hour to appear cannot be solved with a short test.
Which skis this concerns
The FX SVHO and Cruiser SVHO (2014 to 2023) have the supercharged 1812 cc engine, and from 2015 they carry the RiDE system with SCU and RPS. Forum owners describe heat soak as real on supercharged boats: after a long run the intake charge heats up, and the engine can react. That is a common report, but it does not make it the cause in this case.
Why a delay is a clue
A symptom that arrives after a fixed time points to something that builds up. Temperature is the usual candidate, or a voltage that sags as the electrical system warms. A failed sensor tends to show itself at once and set a code. A time-dependent problem suggests a value drifting until it crosses a limit. That is only a direction. It does not say which value.
What to record
Use the M-JET Diagnostic with the data logger, and ride long enough for the drop to happen, which may mean 40 minutes. Record these values in one run:
- Intake air temperature (code 23 belongs to this sensor).
- Intake pressure (the sensor is code 29) next to rpm, since a pressure that stops building shows up as a plateau.
- Throttle position and the accelerator position signals, to confirm that your input does not change when rpm falls.
- Battery voltage.
- Engine temperature (code 15) and exhaust manifold water temperature (code 65).
Then look at the moment the drop begins and ask which line moved a little earlier than the others. A rising intake air temperature before the drop fits heat soak. A voltage sag fits an electrical issue. If the throttle and accelerator signals part ways, the electronic throttle is doing the limiting. If every value looks calm and rpm still falls, you have learned something useful too: the cause is not among the signals the ECU reports.
Check the memory after the event
Read the fault memory right after the ski drops. Some limiting actions leave entries and some don't. If nothing is stored and the live values were normal, the app has reached its limit.
What the scan will not find
The SVHO from 2014 and 2015 has a known weak point in the timing chain, reinforced from 2016 onward, and a diagnostic device cannot detect chain wear. The same applies to the supercharger clutch, to the water path and to anything mechanical in the intake. Heat soak is not a fault either. It is a behaviour, so a log that shows it will not produce a code.
What you end up with is a method, not a diagnosis: log it, compare the lines, change one thing and log again. If the drop comes at 25 minutes every time, make a single change and ride the same route. The page about this rpm drop after 20 to 30 minutes goes into the individual values, and the SVHO diagnostics page lists which models the app supports.
