8.1 water pumps

Great Lakes

Great Lakes

Well-Known Member
Oct 11, 2016
1,444
Lake St. Clair - Michigan (MacRay Harbor)
Boat Info
2008 - Formula 400ss
Engines
Volvo Penta D6-350
So I had new pumps put on last week. They ran great before so it was more of a maintenance decision.

With old pumps the temp would be around 158 while cruising. When I came off plane they would maybe hit 162-164 for a few mins and then settle down to 158, all normal. With new pumps I’m now cruising at 162 and when I come off plane I spike to 175 (port) and 172 (SB) for longer than a few mins. I’m not pushing her hard either. Another huge difference is the steam amount. It’s super noticeable even at the dock warming up or pulling up to other boats to raft up. Way more steam than previous pumps and more than any other boats around me. I know the water is cold still and there will be more steam but this is over the top. So much so all my dock neighbors question it.

Strainers are clear

Mechanic said it’s all normal over text messages but my gut feeling is it’s not normal.

Any suggestions
 
Did you use OEM impeller. Some after market impellers are softer material.
If OEM then perhaps one of the blade is in backwards or one of the old blades had broken off and is stuck in the system or your belt is slipping.
If they changed thermostats at the same time they may have installed a higher temperature one.
Is the water flow the same as before.
 
Hard to say. Was the new impellers properly lubricated before startup? (Liquid soap).

New O rings? Mating surfaces clean? Waterline from strainer to pump clean?
 
I assume "new pumps" means new impellers installed in the old pumps. There really isn't a right and wrong way to install these impellers. If they are reversed they will automatically flip the other way once you start the engine. More than likely, the brass pump housing ends are scored, reducing the efficiency of the pumps. It may be that the old impellers were worn to match the scores in the brass and formed a better seal to pump more water as rotating. Merc's idea of using a soft brass (or bronze) pump housing without any wear plates for the impeller is kinda asking for problems.

I decided to install an aftermarket item which includes stainless wear plates and a bit shorter impeller so it all fits in the stock pump housing. The idea is that steel will be more durable and less likely to score as easily. If the plates become scored just replace the wear plates and throw in a new "special sized" impeller. When I installed the kits in my pumps I really didn't notice any real difference with my engine temps. So even though the pumps were still working ok, the housings were getting quite scored and like you, I wanted to be proactive in my maintenance to avoid failures. I understand your frustration with getting the work done and the engines now run hotter than before!

http://www.amarket.com/im496reb.htm
 
northern said:
Did you use OEM impeller. Some after market impellers are softer material.
If OEM then perhaps one of the blade is in backwards or one of the old blades had broken off and is stuck in the system or your belt is slipping.
If they changed thermostats at the same time they may have installed a higher temperature one.
Is the water flow the same as before.
Click to expand...
I have no idea if they’re OEM.

These are new pumps, not just impellers. The thermostats were not changed and the water flow is the same coming out. Another thing I noticed is that it’s taking a lot longer for water to start coming out when I first start up. Probably 15-20 seconds if I had to guess. It’s borderline to a point I’m thinking of shutting them down but then it starts flowing. In fact I did shut her off the first start after they were change cause I thought something was wrong.
 
Can you read water pressure on your VesselView ?

Stupid question but are the seacocks fully open? Intake screens blocked? Maybe open the strainers and confirm that water gushes in when the seacocks are opened

I wonder if the impellers are mis-matched to the housings??
 
Seapig said:
Can you read water pressure on your VesselView ?

Stupid question but are the seacocks fully open? Intake screens blocked? Maybe open the strainers and confirm that water gushes in when the seacocks are opened

I wonder if the impellers are mis-matched to the housings??
Click to expand...
Not stupid questions. I check the seacocks and popped open the strainers again yesterday. Seems normal.

I had no idea you could check water pressure with VV. I’ll have to try that today.
 
A slight air leak coming from the pump (pinched o ring, cover not properly seated, water line not tight) will effect the efficiency of the pump. You mention that it takes a bit to get water flowing on startup, which again, could indicate that when shut down an air leak is allowing the water in the system bleed down.

As a point of reference: https://www.hardin-marine.com/t-Mercruiser-Gen-7-Sea-Pumps-Suction-issues.aspx

When replacing your stock Gen 7 raw water pump with a Hardin Marine stainless pump care must be taken to avoid air leaks. This is the same if you are rebuilding your existing Hardin pump as the same rules apply. An air leak in any of several spots will cause the pump to not prime on initial start up and cause possible damage to the new impeller.
 
We boat in areas that have sea weed and jelly fish. Some times the screens on the bottom of the boat get plugged off. To clean them I close sea valve, remove hose from suction side of strainer, take hose with no fitting on it place inside hose from valve, clamp securely with rad clamp open see valve turn on potable water. So far it has cleaned the strainers every time. With jelly fish it usually takes a few tries.
 
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