water pump issue

[rickasbury]

I have a 2005 350 MPI in a Rinker we bought around the first of the year. Boat had 98 hours on it when purchased with no maintenance records. So, I have been working through catching up regular maintenance stuff like plugs, changed the oils, serviced the genny, fixed some other minor items etc but had not gotten to the water impeller. Took my neighbors out and as we were launching the boat, the drive belt broke and found the raw water pump frozen up. Got the boat home and pulled the pump and two of the fins had broken off and jammed the pump. The two fins were hole so I did not miss any pieces, So, I get a new impeller and get it all back together, I put the muffs on the foot and fired it up. I have a bravo III and it's a 1/2 loop fresh water cooled engine so I have a thru hull for water pickup and it also draws through the foot. I started it up and watched the temp gauge (did not check to see if water was coming out the motor) and it slowly rose to 175 but kept going so I shut it down. I tried various things, putting it in the water, and finally pulled off the hose that goes to the motor and stuck the hose in there- I figure I have toasted the impeller at this point- but it took every bit of water from the hose and warmed up to around 175 and then stayed there, Thinking I had the system all primed I took it back to the water but it still would not get enough suction to draw water. I did not remove or mess with the feed hoses and nothing is/was leaking. I put water also down the feed hose from the foot to make sure I did not have any debris in the hose and it came out fine. I may grab another seal for the sea strainer but I would think if it was leaking that much air I would hear it. I am really stumped on this one, anyone had similar issue after changing the impeller? I'm going to get a new one and get back down there and pull the pump again but with nothing new to try I can only expect the same result unless there was something wrong with the new impeller I had bought,,,,

 

[Bondo]

I have a 2005 350 MPI in a Rinker we bought around the first of the year. Boat had 98 hours on it when purchased with no maintenance records. So, I have been working through catching up regular maintenance stuff like plugs, changed the oils, serviced the genny, fixed some other minor items etc but had not gotten to the water impeller. Took my neighbors out and as we were launching the boat, the drive belt broke and found the raw water pump frozen up. Got the boat home and pulled the pump and two of the fins had broken off and jammed the pump. The two fins were hole so I did not miss any pieces, So, I get a new impeller and get it all back together, I put the muffs on the foot and fired it up. I have a bravo III and it's a 1/2 loop fresh water cooled engine so I have a thru hull for water pickup and it also draws through the foot. I started it up and watched the temp gauge (did not check to see if water was coming out the motor) and it slowly rose to 175 but kept going so I shut it down. I tried various things, putting it in the water, and finally pulled off the hose that goes to the motor and stuck the hose in there- I figure I have toasted the impeller at this point- but it took every bit of water from the hose and warmed up to around 175 and then stayed there, Thinking I had the system all primed I took it back to the water but it still would not get enough suction to draw water. I did not remove or mess with the feed hoses and nothing is/was leaking. I put water also down the feed hose from the foot to make sure I did not have any debris in the hose and it came out fine. I may grab another seal for the sea strainer but I would think if it was leaking that much air I would hear it. I am really stumped on this one, anyone had similar issue after changing the impeller? I'm going to get a new one and get back down there and pull the pump again but with nothing new to try I can only expect the same result unless there was something wrong with the new impeller I had bought,,,,

Ayuh,.... Welcome Aboard,.... My guess is the end plates of the pump are scored, 'n it ain't pumpin' because of it,....

The end plates, as well as the impeller housin' must be perfectly smooth, or it won't work,...

 

[Bt Doctur]

I put the muffs on the foot and fired it up. I have a bravo III and it's a 1/2 loop fresh water cooled engine so I have a thru hull for water pickup and it also draws through the foot. I started it up and watched the temp gauge (did not check to see if water was coming out the motor)

You can`t have 2 raw water feeds. you would be sucking air.Either you use the thru hull or you use the outdrive for water pickup, but not both

I may grab another seal for the sea strainer but I would think if it was leaking that much air I would hear it.
You would also be taking on water if it was leaking , and no. you would not hear any air leaks.

 

[thumpar]

Follow the feed hose from the seawater pump. I bet it only goes to the thru-hull pickup. The drive may have the slots for water pickup but it should be blocked off.

 

[rickasbury]

Thanks for the replys! First, it absolutely has two water pick ups, thru hull and the foot. I have two hoses going into the sea strainer (which is not leaking so I guess we rule that out). I have the thru hull valve shut off and the muffs on the foot. I swear this worked before and as I recall, the first time I did it water was coming out the thru hull as I forgot to turn that off (or did not think of it). Anyway, I did inspect the pump and there were no grooves in it but will pull it again and check it out. I was hoping there was something real obvious I was missing- bottom line if it's not sucking water, it's sucking air so I just need to find out where and I suppose by now have burnt the new impeller. Again, I did stick my hose in the line that feeds the water pump and it sucked water like there was no tomorrow but perhaps the impeller is damaged enough not to pull water from the foot but move water coming under pressure from the hose......back to it and thanks for the thoughts!

 

[rickasbury]

PS- I pulled the one hose off that goes to the foot thru the transom and reverse flushed that so it for sure does work this way! The service manual also shows this as well.

 

[Bondo]

Thanks for the replys! First, it absolutely has two water pick ups, thru hull and the foot. I have two hoses going into the sea strainer (which is not leaking so I guess we rule that out). I have the thru hull valve shut off and the muffs on the foot. I swear this worked before and as I recall, the first time I did it water was coming out the thru hull as I forgot to turn that off (or did not think of it). Anyway, I did inspect the pump and there were no grooves in it but will pull it again and check it out. I was hoping there was something real obvious I was missing- bottom line if it's not sucking water, it's sucking air so I just need to find out where and I suppose by now have burnt the new impeller. Again, I did stick my hose in the line that feeds the water pump and it sucked water like there was no tomorrow but perhaps the impeller is damaged enough not to pull water from the foot but move water coming under pressure from the hose......back to it and thanks for the thoughts!

Ayuh,..... The rubber impeller pumps generally don't suck air much at all,...

It's a flooded entry water pump, 'n really needs some prime,.... It ain't a positive displacement pump,...
Usually, when ya launch the boat, the impeller is below water level,...

With muffs, ya gotta get some water nearer the impeller than the pick up screens in the drive,...

An impeller pump will suck harder than a bilge pump, but not much,....

 

[thumpar]

You could try closing off the thru-hull pickup and run the hose from the drive directly to the the seawater pump to see what you get. Mine doesn't have a thru-hull pickup or seastrainer and works great.