Depends on if you have "System Check" or not?
I can tell you from experience that System Check does not kill the engine or limit RPM. Buzzer the idiot lights only.
The PCB is comparing RPM to Pump pulses (magnetic). Assume the rpm signal is coming from the control pack
My engine does have a system check which I have verified is working correctly by testing & jumpering the following: Tested overtemp sensors individually in oil bath with thermometer, found starboard side closing too high and replaced it; Jumpered both individually to verify overheat alarm and slow mode activation; Jumpered the fuel vacuum switch for check engine light; Jumpered the low oil switch for low oil light. I have not jumper tested the VRO circuit yet but will as a final verification of the complete warning system. I have recently rebuilt the VRO pump and verified it is operating correctly per the service manual procedure while running engine on a portable tank with a 50/50 oil mix. The circuit board function was the only thing I could not find any description on so your explaination was very much appreciated. It has also allowed me to rule out the PCB (I hope) as the cause of an intermittant loss of power at WOT from 4900RPM down to around 3500RPM and turn my attention toward a fuel issue.
If you are not tired of reading this yet I would like to provide you and any other members an account of the original issue with this motor and what work and replacements have been done to date to solve this issue.
Initially last summer running around 4800RPM headed out to the Suwannee Reef the motor RPM and power abruptly dropped to 2500RPM which is a classic indication of going into slow mode due to an over temp condition. Long story short, we limped back in, cut out trip short and drove back to home base at Weiss Lake in Centre, AL. Started through the diagnostics and determined that the control pack and stator resistances and voltage readings were out of specs. Now was decision time, Motor is 22 years old however compression tests were all consistent and in the 90's so I decided to replace all ignition components, rebuild the fuel system components and replace cooling system components. The following has been completed: Replaced stator, charger/rectifier, OS1 control pack kit with new optical sensor, new spark plugs & wires, three dual coil packs all with CDI brand conponents. Replaced cooling water pump, two new thermostats, the starboard temp sensor, and one blocking diode in the brown temp sensor wire harness. Disassembled, cleaned and installed rebuild kits in six carbs, one fuel vapor pump, the VRO Pump, visually inspected the reed valves behind each carb plate, cleaned the pulse limiter, replaced the incoming fuel filter and tested the fuel vac switch operation and contacts, replaced the incoming fuel line from the squeese bulb to the fuel filter. Fuel bulb is 3yrs old, functional and pumps up hard.
After rebuilds the carbs were linked and synronized, the timing deg pointer was set using the piston stop method on #1 cylinder, throttle linkage and timing advance plate was set per the service manual, idle timing was set to 6 deg ATDC at 950 RPM and WOT timing was set at 20 deg BTDC at 5000RPM using a timing light with boat sitting on trailer backed down ramp into the water. After setting timing the boat was lake tested and made several short trips around the cove running at 4900RPM after which the RPM and power dropped to around 3500RPM and was not running smooth. Pumped squeeze bulb & made several stops and starts but the results were the same. Based on all of the above information, replacements adjustments, testing and verifications my conclusion is that this is a fuel flow issue at WOT posibally due to one of the local fuel hoses or pulse limiter collapsing or sucking air. My next step is to replace all of the local fuel hoses then install a new pulse limiter & hose & new hose clamps.
If anyone has read this far by now, I really do appreciate your time and certainly would appreciate any advise, suggestions or opinions as the possible cause of this intermittant loss of power at WOT. Please Reply
