8.1L raw water pump

N

Nmor830

Member
Sep 12, 2016
90
Channel Islands
Boat Info
2008 340 Sundancer
Engines
8.1l Mercruisers
My troubled child starboard engine raw water pump failed again with only about 25 hrs. on it. This is a refurbished pump. Prior I installed another pump from same vendor and the engine ran about 10 degrees hotter then the port. I wasn’t comfortable with that so they sent me a replacement which is the current one that just failed.
I guess the first step would be check impeller. Was running at about 2900 rpm when the sound of the engines changed. I noticed the temp on the St climbed to about 180 before I shut it down. Hope I didn’t do any further damage.
Limped back and once tied up I started the St and noticed hardly and water flowing from the exhaust.
If the impeller looks good any other suggestions? Are these pump rebuild kits worth doing?
Thanks,
Nick
 
Nmor830 said:
My troubled child starboard engine raw water pump failed again with only about 25 hrs. on it. This is a refurbished pump. Prior I installed another pump from same vendor and the engine ran about 10 degrees hotter then the port. I wasn’t comfortable with that so they sent me a replacement which is the current one that just failed.
I guess the first step would be check impeller. Was running at about 2900 rpm when the sound of the engines changed. I noticed the temp on the St climbed to about 180 before I shut it down. Hope I didn’t do any further damage.
Limped back and once tied up I started the St and noticed hardly and water flowing from the exhaust.
If the impeller looks good any other suggestions? Are these pump rebuild kits worth doing?
Thanks,
Nick
Click to expand...
I replace my Raw water impellers every other season Sometimes every two seasons depending on the hours I put on them. I never had a problem with a rebuild. What shape is the wear plate in? have you ever changed it? And yes it's worth doing!
 
Same here. Replace every 2 years along with BOTH wear plates. If you any scoring at all in the pump, you will have problems. Don't forget to lube up the new impeller with dish soap! Yes they are worth doing compared to replacing a pump!
 
Thanks for the reply’s. Time to down there and be a contortionist. I’m not sure it’s starving for water the strainer and bowl are clean.
 
scoflaw said:
Sounds like Bravoitus, Pump is starving for water and burning up. Just a guess
Click to expand...

I was assuming that the poster's setup was twin inboard V-Drives so Bravoitus would not be applicable. He did mention that the strainer was clear - not normal to have a sea-strainer with Bravo outdrives.

It is odd that pump would fail at 25hrs. It would be worthwhile to remove the heat exchanger end caps to ensure that nothing is blocking the water supply side of the exchanger. I had the rubber gaskets on mine degrade to the point of breaking apart and plugging much of the water flow on both ends of the cooler. That made the engine run 10-15 degrees hotter than the other (that had the cooler replaced about 10yrs prior). Restriction of water flow either before or after the pump can cause it to overheat.

When you say it "failed" can you describe its condition. What is the condition of the rubber impeller, the bearings for the impeller shaft, and the housing itself - are there deep grooves in the bronze or do you have stainless wear plates? If the impeller looks fine and there are no wear plates, but the housing is grooved there is a kit available which provides stainless wear plates and a revised impeller to improve pump pressure.
 
Pulled the raw water pump and got the rebuild kit with new impeller and wear plates. Checked flow from the “Bravoitis” by hooking up shop vac and blowing air through the water line from where it connects to the pump. Lots of bubbles coming up so assumed no clogs from there to the pump. Primed pump started engine and still no water flow? Any idea where to check next. Heat exchanger? Already replaced the port side some time ago. It never caused flow to stop but just started leaking. This ones 12 years old and in salt. Any suggestions would be appreciated.
Thanks,
Nick
 
Nick,
Just to confirm, do you have bravo's or are the pumps connected directly to sea strainers? I personally would start slight loosening each hose , one by one, to see where u are getting water flow, and when u r not
The heat exchangers are easy to check simply by 1 screw at each end. But get new gaskets first. I would find it hard to believe they are that clogged!
The main goal going foward is to follow the path to and from the pump and determine where the stopage is! Follow all the hoses carefully.
 
Nmor830 said:
Pulled the raw water pump and got the rebuild kit with new impeller and wear plates. Checked flow from the “Bravoitis” by hooking up shop vac and blowing air through the water line from where it connects to the pump. Lots of bubbles coming up so assumed no clogs from there to the pump. Primed pump started engine and still no water flow? Any idea where to check next. Heat exchanger? Already replaced the port side some time ago. It never caused flow to stop but just started leaking. This ones 12 years old and in salt. Any suggestions would be appreciated.
Thanks,
Nick
Click to expand...

Start at the through transom supply. Take the hose off where it connects to the engine and lower it into the bilge.
How much water come out?
 
tony1b2000 said:
Nick,
Just to confirm, do you have bravo's or are the pumps connected directly to sea strainers? I personally would start slight loosening each hose , one by one, to see where u are getting water flow, and when u r not
The heat exchangers are easy to check simply by 1 screw at each end. But get new gaskets first. I would find it hard to believe they are that clogged!
The main goal going foward is to follow the path to and from the pump and determine where the stopage is! Follow all the hoses carefully.
Click to expand...
tony1b2000 said:
Nick,
Just to confirm, do you have bravo's or are the pumps connected directly to sea strainers? I personally would start slight loosening each hose , one by one, to see where u are getting water flow, and when u r not
The heat exchangers are easy to check simply by 1 screw at each end. But get new gaskets first. I would find it hard to believe they are that clogged!
The main goal going foward is to follow the path to and from the pump and determine where the stopage is! Follow all the hoses carefully.
Click to expand...
 
Not bravo’s. The pump is connected directly to the strainers. Removed and cleaned strainer plastic housing and strainer. I blew air through the hose that connects to the pump and got plenty of bubbles coming up from under boat. Also after priming the strainer water flowed into the pump when opened the blue primer screws. I think everything from the intake to the pump is clear. Pulled one side off the heat exchanger, the gasket was a little deformed but still intact. Didn’t check the other side. Ordering new gaskets. I guess I’ll start pulling one hose at a time. Just seems weird a hose would clog?
Thanks,
Nick
 
techmitch said:
Start at the through transom supply. Take the hose off where it connects to the engine and lower it into the bilge.
How much water come out?
Click to expand...
Mine connects to a sea strainer. Removed and cleaned the strainer and plastic housing. Water flows from the strainer to the pump. Check by removing the blue primer screws. Going to star pulling hoses and checking one at a time.
Thanks,
Nick
 
scoflaw said:
Sounds like Bravoitus, Pump is starving for water and burning up. Just a guess
Click to expand...
Don't know much about that pump but i agree he's starving for water, a good up grade might be a through hull !What do you think?
 
20190326_172048.jpg
Hi Nick,

I did not mean to confuse. Hoses don't normally clog except on the intake of the strainer. What I meant by loosening or removing hoses to check water flow, was to find the object causing the problem (Heat exchange, oil cooler, etc.. By the way, when were your exhaust manifolds last changed?
There is a 90 plastic elbow on mine feeding into the bottom of the manifold from the raw water pump and they were totally clogged from rust particles! But in my case, I was getting an overheat issue.... This may not be your case. I am simply showing you that a clog can be anywhere! Trace the hoses and you will get to the bottom of it..
 
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