Gentlemen;
I'm not familar with the latest "jargan" on cams (single/dual pattern) and "overlap" is a hard concept to explain, but I'll try.
With (high lift/long duration) cams there is a point in time between the intake and compression strokes where the intake valve has not fully closed (low speed) and some pressure is lost between cycles. As the assembly rotates there is also a point in time between the power and exhaust strokes where the exhaust valve opens slightly ahead (low speed) losing there as well.
As the engine's speed increases, the 'time' of these events lessens, because "real time" has stayed the same.
This is why compression (pressure) readings are lower with these cams and engines with them can't idle well.
At some point in real time these events become so small (higher engine speed) that they can't affect and this is where the "power curve" begins.
In marine use, the engine must idle/function @ low speed well, so I would not recommend a really "radical" camshaft etc.
Good luck.
