"John,
I don't know a d
"John,
I don't know a damn thing about Volvo engines or outdrives....but I've had a LOT of Merc experience, including some performance products. Not that it's normal....but on some boats, particularly those with straight thru exhaust systems....I've seen both the flappers on the outside of the pipes....but I've also seen balls INSIDE the pipes...and this is to keep cold water from flushing backwards up the exhaust when the boat is going in reverse. Needless to say, the system is already water cooled...but sometimes a back-pressure from being forced up the exhause while the boat is going backwards, can cause too much reverse flow...and this can actually enter the combustion chamber if the exhaust from the engine is in common with the water flow...which most marine systems are. And...cold water hitting the hot exhaust valves...and you've got a BIG problem....like possibly a bent valve, or even the loss of a valve seat down into your combustion chamber....meaning enging overhaul time if you're lucky. Maybe even a NEW engine if you're not!! Anyway....I don't know if your ball is for this purpose...but you might be able to deduce if this is plausable by just looking at the location of the ball...the exhaust, and the what that ball might be doing if it were floated by incoming water. Would it 'block' that water from going further up your exhaust system an possibley keep the flow out of your heads? If so, then it's a pretty safe bet that's what it's there for. So....just speculation and conjecture, but I'd love to know if that ends up being your logical best explanation. Good luck, Tom D."
