Today I removed C44, C45 & C39 from the board and tested with 2 different ESR meters and they both seemed fine.
Also, I read the data sheet for the lm386 where it mentioned a bypass capacitor from pin 7 to ground.
I experimented with some old caps I have lying around. 47uf 10v, 100uf 10v, 220uf 10v, 100+220 in parallel, 1000uf 25v.
Each time the capacitor made a difference with a delay in the time it took for the motorboating to start but it inevitably happened.
The pad at pin 7 came off and pads for C39 are starting to lift.
The manual clearly states that "The amplifier in our kit with a gain of 150 is shown in Figure 5." I've noticed a couple of things:
1. Figures 4B with gain = 200 & Figure 4C with gain = 150 - Both show a bypass capacitor at Pin 7, value = ? yet both Figure 5 and the PCB board show nothing.
2. Coming off Pin 5 to ground, Figures 4A, 4B & FIGURE 5 show capacitor - resistor then ground yet Figure 4C with gain = 150 it shows resistor - capacitor then ground.
3. Resistor values are the same.
Also, re this data sheet
https://www.ti.com/lit/ds/symlink/lm386.pdf diagrams showing a speaker connected have a 250uF capacitor before it where as C43 in this kit has a 470uF.
Thoughts anyone