1998 Bravo 7.4 Non-Magnum - Have Ruined 3 Impellers w/o ever putting the boat on the water...

[San_Diego_SeaRay]

...and now I just ruined the 4th one....

Happy 4th Weekend. Hope everyone is enjoying themselves!

Long story short:

• Boat hasn't been in the water >4 years due to a bad gas tank that had to be removed from under the deck and replaced (my projects are stretched out for maximum fun )
• Over the course of those 4 years, I have variously attempted to run it on a sketchy water supply although it should have been adequate for the low RPMs (it was off a 500 gallon water tank that recycled the water. Didn't have access to an actual proper water supply)
• I had so far ruined 3 impellers and replaced them
• On Tuesday, I finally towed the boat to a proper water supply and ran it. It ran great. Sucked up all the water and didn't even hint at overheating
• On Wednesday, I dropped her in the water and she overheated while at the dock to 225 degrees
• I pulled her out, put her on muffs, and she wasn't sucking in water any more
• Today I took the sea water pump housing apart and found that the "key" of the impeller had been stripped (yes, it was a cheap knockoff impeller)

So of course my next step would be to buy a new impeller, this time a genuine OEM impeller.

My question is: Looking at the pictures I've attached and the history of ruining impellers, do you think the housing has as much to do with the problem as anything? There are groves in the walls but there are no cracks. I should also say that the lower housing hose (the outlet) was leaking a small but steady (drip drip drip) amount of water. No matter how much I tightened the hose clamp, it continued to drip. Thanks in advance!

 

[Scott Danforth]

Are you using muffs and good water pressure on a hose or are you attempting to suck water from a bucket?

 

[San_Diego_SeaRay]

Are you using muffs and good water pressure on a hose or are you attempting to suck water from a bucket?

No, not out of a bucket. With muffs off a hose w. fair to good water pressure.

EDIT: I see why it might have been confusing. The water tank was just the supply where the water came from. I didn't put the sterndrive in the water tank. Water was pumped out of the water tank and through a hose with so-so water pressure. But should have certainly been enough to lubricate and cool the impeller, I think.

 

[Scott Danforth]

And the hose is on full? Hose is 5/8 or larger?

 

[San_Diego_SeaRay]

And the hose is on full? Hose is 5/8 or larger?

Yep. On full and was a 5/8" hose. Here's a picture of the actual setup. You can see the 500 gallon tank behind the boat. Was pumped to the boat by one of those Jabsco-type pumps you see on boats and RVs.

 

[Bondo]

Ayuh,.... The water tank is to low,....
Raw water pumps won't suck, but must be fed,....
'n the pump yer feedin' it with is waayyy to tiny,.....

 

[San_Diego_SeaRay]

Ayuh,.... The water tank is to low,....
Raw water pumps won't suck, but must be fed,....
'n the pump yer feedin' it with is waayyy to tiny,.....

Ok gotcha thanks. However, I ran the boat on Tuesday off a municipal hose w. plenty of water and pressure. Ran perfect. No overheating. So I guess the question is, does a housing w. some grooves in it but not cracked usually have performance problems or is that not a suspect here? If not, I'll just buy a Quicksilver impeller and replace it.

 

[CayugaCobalt]

How did the earlier ones fail? Keyway too? Or paddles fell off?

 

[Paintman1960]

Ok gotcha thanks. However, I ran the boat on Tuesday off a municipal hose w. plenty of water and pressure. Ran perfect. No overheating. So I guess the question is, does a housing w. some grooves in it but not cracked usually have performance problems or is that not a suspect here? If not, I'll just buy a Quicksilver impeller and replace it.

Why not just replace all of it ?

 

[Scott06]

Ok gotcha thanks. However, I ran the boat on Tuesday off a municipal hose w. plenty of water and pressure. Ran perfect. No overheating. So I guess the question is, does a housing w. some grooves in it but not cracked usually have performance problems or is that not a suspect here? If not, I'll just buy a Quicksilver impeller and replace it.

I think you’d be ok reusing that housing. As you determined the issue was inadequate water supply. If the three impellers you roached essentially running them dry did any of them loose vanes? If they did you need to find the rubber pieces so they dont clog thee thermostat or riser passages

 

[tank1949]

...and now I just ruined the 4th one....

Happy 4th Weekend. Hope everyone is enjoying themselves!

Long story short:

• Boat hasn't been in the water >4 years due to a bad gas tank that had to be removed from under the deck and replaced (my projects are stretched out for maximum fun )
• Over the course of those 4 years, I have variously attempted to run it on a sketchy water supply although it should have been adequate for the low RPMs (it was off a 500 gallon water tank that recycled the water. Didn't have access to an actual proper water supply)
• I had so far ruined 3 impellers and replaced them
• On Tuesday, I finally towed the boat to a proper water supply and ran it. It ran great. Sucked up all the water and didn't even hint at overheating
• On Wednesday, I dropped her in the water and she overheated while at the dock to 225 degrees
• I pulled her out, put her on muffs, and she wasn't sucking in water any more
• Today I took the sea water pump housing apart and found that the "key" of the impeller had been stripped (yes, it was a cheap knockoff impeller)

So of course my next step would be to buy a new impeller, this time a genuine OEM impeller.

My question is: Looking at the pictures I've attached and the history of ruining impellers, do you think the housing has as much to do with the problem as anything? There are groves in the walls but there are no cracks. I should also say that the lower housing hose (the outlet) was leaking a small but steady (drip drip drip) amount of water. No matter how much I tightened the hose clamp, it continued to drip. Thanks in advance!

View attachment 344489View attachment 344490View attachment 344491View attachment 344492

defective housing or not getting enough water to lub while cranking up.

 

[San_Diego_SeaRay]

How did the earlier ones fail? Keyway too? Or paddles fell off?

All of the others had keyways intact and it was the paddles disintegrated. This is the first one that failed at the keyway.

I think you’d be ok reusing that housing. As you determined the issue was inadequate water supply. If the three impellers you roached essentially running them dry did any of them loose vanes? If they did you need to find the rubber pieces so they dont clog thee thermostat or riser passages

Yeah I'd rather not buy another housing kit if I don't have to. But, that's exactly what I did this morning. So at least I'll be able to move forward with peace of mind.

I don't know that I ever determined that there was inadequate water supply. Remember, I ran the boat on Tuesday with a definitely-adequate water supply on a hose w. muffs. Then on Wednesday I launched it in the bay. That's when it overheated.

If grooved walls in the housing aren't a suspect here then you gotta seriously wonder about the quality of these off-brand impellers. I mean I can understand that they may not last as long as OEM, but less than one hour? Woof.

 

[Scott Danforth]

Yep. On full and was a 5/8" hose. Here's a picture of the actual setup. You can see the 500 gallon tank behind the boat. Was pumped to the boat by one of those Jabsco-type pumps you see on boats and RVs.View attachment 344493

If you had a proper pump, that 500 gallon tank would only last a few minutes. No way that RV pump has enough pressure or flow.

You need 15 gpm at 60+ PSI. That RV pump is 3 gpm at 0 psi and 0.5 gpm at 50 psi.

You would need a 2hp gas powered pump

 

[San_Diego_SeaRay]

If you had a proper pump, that 500 gallon tank would only last a few minutes. No way that RV pump has enough pressure or flow.

You need 15 gpm at 60+ PSI. That RV pump is 3 gpm at 0 psi and 0.5 gpm at 50 psi.

You would need a 2hp gas powered pump

Understood but the water gets collected and recycled and put back in the tank real time, so the volume is indefinite (less evaporation).

Yeah they should have a bigger pump. That station was built to wash boats, not run them. But in a pinch I asked to use it. I have to say though, when you look at the output from the hose, it looks pretty much like the output of a normal hose. But I won't use it again. Lesson learned.