Honda 8 - Replaced impeller, left the old one in there

Hello,

I purchased a used Honda 8, and never having run a Honda before, I wasn't sure what to expect to see out of the pee hole. I got the thing a couple miles from the harbor and the water stream completely stopped, smoke coming out the hole, which was fine as this was it's test cruise (meaning I rowed/napped my way back).

Upon investigation, I found a new impeller in the water pump, which I expected find there, but looking closer I found the remnants of the old impeller as well stuck in the pump housing!

Several days later I have found and removed remnants from the exhaust manifold and blown out the water tube in the lower unit with compressed air. Both water hoses are clear. What's inside the block is unknown to me.

During last night's test run, I found that the motor produced a steady stream initially, however the stream seemed weaked at the end of the cruise (possible from an undiscovered chunk of rubber blocking a passage.) Coming down from a high throttle to a low one the stream would momentarily stop, and smoke would appear for a second before the stream resumed.

Is there a volumetric amount of water this thing should be pumping at idle, that I could check? Can I get a cup of exhaust water and check it's temperature? The water wasn't too hot for me to put my hand under the stream (after idling after my cruise). If any debris makes it to the exhaust manifold, are the passages in the engine block large enough to allow it to leave the cooling system?

Thanks, I appreciate any help.

I will try and post some video tomorrow, if I can figure out how.