A noise at the engine, then the fuel primer bulb lost pressure?
From what you've said above, I assume the VRO is new so that most of the following is unlikely, BUT it is worth mentioning.
That would need to be either a carburetor float needle valve failing which would allow that specific carburetor to flood..... OR a portion of the VRO failing that might allow fuel to backflow to the oil side and to the oil tank. I've encountered this in the past with older model VROs but don't know if this is still possible or not..... OR a failure exists with the VRO that is allowing fuel to flow to the pressure line that connects the VRO to the crankcase (block).
Remove carburetor face plate to observe possible carburetor flooding. Remove VRO oil line to check possible fuel to oil backflow scenario. Remove VRO pressure line to check possible fuel to crankcase flow scenario.
Any air leaks would result in fuel leaks at the same location.
Note that holding the fuel primer bulb in the upright (vertical) position causes the two primer bulb valves to fall into their proper positions (normal). Many bulbs do not function properly upon their initial prime (initial meaning bulb and lines being empty).
Possibly a portion of your problem is that the anti siphon valve is stuck open and is allowing fuel to siphon backwards from the engine to the fuel tank......
(Fuel Anti Siphon Valve)
(J. Reeves)
Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.
NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.
The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.
The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.
