Shredded Impeller

[bengaltiger14]

2005, Sea Ray, Mercruiser 5.0L MPI

So my wife decided to crank the boat up while beach on sand for over 20 minutes, thus shredding the impeller. I did not realize it until we took off and the gauges were reading only 1.4 or so psi at 35 mph. It did overheat at idle but there was enough water pressure to cool the engine off at higher RPMs. So, I disassembled to water pump to find the impeller shredded with only 1 vane intact. I found 2 other vanes within the water pump housing but did not find the remainder. I checked the hoses and thermostat housing. I reassembled the water pump and the pressure appears to be ok. Should I be concerned???

 

[alldodge]

2005, Sea Ray, Mercruiser 5.0L MPI

So my wife decided to crank the boat up while beach on sand for over 20 minutes, thus shredding the impeller. I did not realize it until we took off and the gauges were reading only 1.4 or so psi at 35 mph. It did overheat at idle but there was enough water pressure to cool the engine off at higher RPMs. So, I disassembled to water pump to find the impeller shredded with only 1 vane intact. I found 2 other vanes within the water pump housing but did not find the remainder. I checked the hoses and thermostat housing. I reassembled the water pump and the pressure appears to be ok. Should I be concerned???

The other pieces are probably still there and could cause an issue later. Did you look in the power steering cooler?

 

[bengaltiger14]

No I have not. I will check that today.

Out of curiosity, around what should the water PSI be reading at idle and WOT?

 

[alldodge]

No I have not. I will check that today.

Out of curiosity, around what should the water PSI be reading at idle and WOT?

Can find nothing in the manual which indicates pressure.

 

[thumpar]

Is this an engine driven pump or in the drive? When mine when with an engine driven pump I took the hose off the pump and put the garden hose in the hose at the thermostat and backflushed it. I got lots of pieces.

 

[bengaltiger14]

I will try that. It is engine driven.

I took the boat for a run yesterday and it was getting good water pressure (14 psi when cruising at around 25 mph). After 30 minutes or so, I checked for leaks again (I did this initially when running boat on water hose) and noticed a trickle coming from the output hose from water pump. I think this is where it is coming from. The area around my engine is so tight I can't just get down there and look. I then noticed the water pressure INCREASE to around 40 PSI and the engine temp dropped from 165 to about 130. Think a piece of the impeller has lodged the thermostat open? Any ideas on this increasing water pressure? I'm not sure what the normal range is.

 

[camalot]

The later PCM555 has a sensor on the sea pump and will sound the alarm and throw a code if it see's 42psi or lower.So I would assume it needs to be 42psi and higher

 

[achris]

42 psi is the fuel pump pressure, not the seawater pump pressure! I haven't seen a value for the low pressure alarm setting. I also know that the pressure (and volume) will vary according to the drive ratio...

I'll keep looking for a spec and get back here if I find one...

Chris.....
EDIT: Found it... I have the print out of the parameters set in the ECM from my engine. Seawater pump spec is set at 0.5-15psi. So if the pressure is less than 0.5psi you'll get a low pressure alarm, and if it's higher than 15psi you'll get a high pressure alarm... I also have a printout from when it was idling, pressure was 4.40kPa (0.64psi) and at 4950rpm, on the rev limiter it was 88.21kPa (12.8psi)....