Shredded Impeller-How to Backflush?

[Sumer]

My 350 Mag MPI was overheating and had a totally shredded impeller.
I have a Bravo One so the impeller was mounted in the front of the engine.
I have a new one but have not reinstalled yet. I need to know:
What is the process to backflush to be sure all the pieces are out?
Do I have a check valve and what does it do?

 

[mikeneal]

Re: Shredded Impeller-How to Backflush?

Is it apart, first off take it apart and see if there are missing pieces, maybe you got lucky and the impeller did not tear apart. T-stat, t-stat housing and power steering oil cooler are common areas for pieces to migrate too.

 

[HT32BSX115]

Re: Shredded Impeller-How to Backflush?

Howdy,

I wouldn't say there's a procedure per se',

You probably have a power steering and oil cooler. Raw water usually always goes thru the power steering and/or oil coolers prior to the closed cooling heat exchanger (if installed) or the engine .
The oil cooler has holes in it that would prevent previous impeller debris from passing through.

When I disconnected the discharge hose going from the raw pump to the oil/power steering coolers on mine I found my oil cooler literally CRAMMED full of pump remnants from a previous pump failure.

That's the place to look. "Backflushing" the system would have not dislodged any of the stuff in the oil cooler. You'll need to remove both the oil cooler and power steering cooler(if installed) and look for yourself.



Regards,



Rick

 

[TilliamWe]

Re: Shredded Impeller-How to Backflush?

I'm sure DonS has it in a manual link somewhere, but the procedure should be,

Remove the pump, take it apart and count the remaining blades. Place the outlet house (the softer of the two) somewhere where you can sort of see the end, if any pieces come out. Then, remove the hose from the port side of the thermostat housing that comes from the pump. There are no check valves in your hoses. If you can, shine a light into the thermostat housing and look for any pieces lodged in it. Then spray water down that hose with your garden hose handle on the setting that allows it to spray the most volume and pressure. Count the blades that come out of the pump outlet hose that you positioned so you can sort up see it. If the total number of blades don't add up to the muber of blades on the new impeller (7 I think) then you may have to take components apart.

Hope that helps.

 

[Fishermark]

Re: Shredded Impeller-How to Backflush?

I have essentially the same engine with the engine mounted pump - Here's where the pieces ended up when my impeller shredded:

Since then I've learned to replace the impeller every other year BEFORE that happens.

 

[HT32BSX115]

Re: Shredded Impeller-How to Backflush?

I have noticed that some boats either don't have oil coolers (and don't have power steering at all) or the oil & PS cooler are in the raw water line BEFORE the raw pump.

In that case you get what happened in the excellent photos above. If you're lucky, they don't get past thermostat.

I was luckier. Mine didn't get past the oil cooler.

 

[TilliamWe]

Re: Shredded Impeller-How to Backflush?

Excellent photos Fishermark. I didn't get to take pictures of mine.

 

[Sumer]

Re: Shredded Impeller-How to Backflush?

Thanks for the help. We found our power steering cooler crammed with little pieces of the impeller. About 80 little pieces in all. We did flush and checked the entire system. Looks like we got them all. Definitely wont wait 5 years to change the impeller again.