HELP! Raw water pump working intermittently??

[tony1b2000]

What can cause the raw water pump to stop pumping altogether (loose prime)? When I attach a hose to the flush kit for a few minutes, I can get the pump to work again. Then occasionally it seems to loose prime or is sucking air and I get ZERO psi. Impeller is new!

Work done prior to launch
=================
1. Replaced both impellers ( 2 engines) on the raw water pumps (No cracks, scoring not bad).
2. Had both Bravo drives pulled just to check bellows for water and grease spline.
3. Replaced ALL manifolds and risers

I did everything except pull the drives. I am wondering if someone forgot a gasket when putting one of the drives on. Suggestions???

 

[Snapon24]

Did you use oem impellers or cheaper aftermarkets (Sierra). I had a friend that had the hubs spin inside the rubber on Sierra impellers after only a few hours of use.

 

[Brite Idea]

Bravo III drive are a PITA on muffs. They do better submerged and even then you need to let them soak for 15 minutes before starting. Your boat is a 2010 and I'm guessing the water pickup is through the drives? It's possible you don't have a problem at all but those water hose through the transom assembly are prone to corrosion. When the boat is in the water what does the Smartcraft water pressure read?

 

[liv2ryde100]

when i had my last boat it had a bravo three drive. it pulled seawater in through it obviously, but the boat also had a secondary pickup that was a thru hull fitting. maybe u have the same setup which would explain why air is coming into the pump when just using ear muffs

 

[liv2ryde100]

hopefully u didnt run it too long or u may have smoked those impellors already.

 

[tony1b2000]

Both impellers were new OEM. Very strange that I ran the boat for a 20 min spin the harbor. Accidentally got snagged on a lobster pot. Did the forward / reverse action to clear the line. one minute later, engine alarm, overheat. lost psi on port raw water pump. Limped back on one engine. At dock, Attached the flush kit and got psi back!! Like I lost prime.

Frustrated, I spoke to merc. They suggested their shorter impeller and wear plates ( Like Hardin carries ). They said any scoring can cause a problem. When I pulled the pump apart, there was some scoring. Hoping this new kit solves the problem.... I cant believe that the hub would spin that easily. Has anyone cut one apart? I would think they have some splines attached the vaines...

So glad Merc stepped up and now has these inner and outer plates with a 0.030 shorter impeller. Should make our pumps last a lot longer!

Mercury individual part numbers (can get a kit)
-----------
Outer wear plate: 8M0114788
Shorter impeller: 8M0103389
Inner wear plate: 8M0072979

BTW, when I pulled the pump to rebuild to put in the new kit, I was in the water. Plenty of water can in the hose from the lower unit. Thus, I don't think anything is kinked. This type of work is not for the faint of heart (in the water service). Just have some wood plugs handy and it's a fine to do. Just make sure your bilge pumps are working fine!