Re: 10 Million Dollars For The Person That Can Answer This Question !!!!!!
OK! A little lesson on Force cooling systems and exhaust idle relief.
The two holes in the back of the shroud are idle relief holes. Their PRIMARY purpose is to relieve backpressure when the engine is sitting low in the water--like at idle. Because Force are 2 cycle engines, excessive backpressure will cause exhaust to blow back into the cylinders, stalling the engine. So: This keeps backpressure low, improves the idle and prevents the engine from stalling.
Now: water is delivered from the water pump to the block via the matching plate. It is delivered to the exhaust cooling cavity near the bypass (or hole in newer blocks where the bypass used to be). This is where the dog-leg in the exhaust cover is. The water first circulates through the chambers surrounding the exhaust because it is critical to keep this area cool. It then circulates around the cylinders. This dumps into the exhaust and is blown out the snout with the exhaust gases.
When the thermostat is closed, very little water is passed through a weep hole in the thermostat so the bimetal plug can sense the temperature. When the bimetal plug gets hot enough, it expands, opening the thermostat. Then, full water flow is passed through the head from top to bottom. Actually, the plug is not bimetal, it is a liquid metal --I really don't know what metal or compound --like mercury or gallium that expands radically with heat.
In the bottom of the match plate, there are several water passage circuits to dump this water inside the midleg, around the exhaust tube. One dumps water from the bottom of the head just above the idle relief. All this water cools the exhaust tube and the midleg and also helps to reduce some exhaust noise.
Now comes the interesting part: This water will spray out of the idle relief holes at idle because it is not a lot until the thermostat opens, and it is blown out along with the relief exhaust. However, There usually is a gasket on the lower exhaust tube which semi-seals the midleg. At higher speeds, enough water is pumped into the midleg to possibly fill it and water then FLOWS out the idle relief holes.
SO: When testing on muffs, water will preferentially flow/spray out the exhaust snout and the engine may or may not have water issuing from the idle relief. Since it is usually difficult to supply with a garden hose the amount of water that the pump will deliver, it will usually take a long time for water to issue from the idle relief holes: The block exhaust chest and cylinder water passages must be filled before the idle relief will get water. If you have a good water supply and water is spraying forcefully out around the muffs, you will usually get water issuing from the idle relief.
