Sat once putting in the water I checked and found no water out the tips
After getting back to the marina and replacing the impellar i tried my best to back flush the hoses for misc peices.

Everything seemed ot flow fine.
So off we went up river.
Once I got up to prescott I was hesitant about the partrol boats so I closed the tips. Teague TCm 450's. after the card stop we took off and at the enxt no-wake zone I smelt burning rubber
Come to find out it was us and i shut down. The port motor, left bank, as you are looking from the front of the engine back, exhaust hose from the y-pipe to the tip was smokin.
Felt the hose and it was very THIN. Not totally blown out yet, but real thin.
took off the hose to hte manifold, stock 502 block. Started back up and water flow seemed fine. top of manifold was never to hot to hte touch. pulled the same hose off hte starboard motor but on the right bank and the water seemed to match between both motors.
Problem now is with everything hooked back up and watching the exhaust tips, the external flaps just did not seem to have as much pressure or water flowing out as the other 3.
Questtion is? Can these tips be cloged with peices of the impellar that when i closed the internal flap it reduced the water flow enough to casue the back pressure to melt the exhaust hose closest to hte tip??
Looking for insight before tearing it apart

Hugh no way that happened. If you take a allen wrench and undue the bolt and slide out the flapper you will see why. When you pulled out the water pump was it hole or in pieces? If in pieces I would guess that you still have something in lets hope one of your coolers. I would pull them out and actually look through them. Or you could have something in your riser or t-state???

Jon

Thats what i was thinking also Jon
But it is so weird that wehn I closed the tips that was only when it melted the hose.
Motor never got hot.
manifold was always just warm to the touch, like always.
Flow matched the other motor that did not have impellar problems
I kept the r's under 3500 when running with it closed. actually was only at 28-3000
that is why I was thinking the holes inside the tip might have blockage.
And i do NOT want to take off the tips. You know how much of a PITA they are to install

Guess once I get anther truck I will have to pull it home and pull out all hoses to flush independantly of each other
I dont beleive the t-stat is blocked since hte motor stayed at temp all day at any speed

In a stock waterflow config, you go from the raw pump to the cooler, from the cooler to the huge Merc Tstat housing with all the different lines going everywhere.

A stock cooler will usually stop most of the rubber chunks and they sit right there. If you remove the hose that goes from the cooler to the tstat housing and remove the hose at the raw pumo that goes to the cooler, then you can backflush with a garden hose on high. The chunks usually all come back out.

If you have a different style cooler, it may allow rubber to pass which will put it in the motor.

I had to backflush one of my Cat diesels last weekend. SeaCock lever had bent, and it wasn't open all the way even though the lever looked to be in the right position. Motor got warm at fast cruise and by then the impeller had gotten hot and cracked. Was still working, but lost a handfull of the tips of the rotors later that day and had to backflush. Was far easier than I had feared. Same basic procedure, though. (the heat exchanger has a mass of tiny tubes that I knew would not pass the rubber so I have no concerns about it having gotten any farther).

I've wondered if it might be a good idea to put a chunk trap after the raw pump. Kind of like a high-flow basket filter or something. something easy to clean - maybe even a glass bowl so you can see in it. Not anything as dramatic as another strainer.. Any ideas?