Impeller Housing Galvanic Corrosion and Pump Bolt Thread Size

[ross l]

I pulled a pump because impeller housing ringing. The ringing was getting severe. I think I will have to replace the housing because of the galvanic corrosion issue. It seems like the whole housing is getting smaller evenly rather than a few raised spots that I've seen on other posts. Anyone have a similar experience?

One of the bolts came out very hard and had buildup on the threads. I want to run a tap into that hole to clean the threads. I think they are 10mm X 1.25. Anyone know the thread size?

Thanks

 

[mrcleanr6]

I pull my pumps down to the transom plates every spring to grease all the bolts. Imo it should be routine maintenance. Once you do it you can do it in 5 min. If you dont what you end up with is seized bolts and snapped off heads. Once the pump liner starts getting corrosion behind it then it time to replace that.

 

[Dan Ruehl]

I pulled a pump because impeller housing ringing. The ringing was getting severe. I think I will have to replace the housing because of the galvanic corrosion issue. It seems like the whole housing is getting smaller evenly rather than a few raised spots that I've seen on other posts. Anyone have a similar experience?

One of the bolts came out very hard and had buildup on the threads. I want to run a tap into that hole to clean the threads. I think they are 10mm X 1.25. Anyone know the thread size?

Thanks

View attachment 134691

Same issue…did you find the correct tap?

 

[ross l]

I did not get the correct thread size and did not use a tap.
I did clean both male and female threads. Then I carefully used the bolts as a tap using lubrication. I screwed them in and backed them out frequently, just like you would do with a tap.
I think I got some shavings but I don't recall exactly.
It worked without issue.
I will see if it is still good shortly because I need to pull them for inspection before I put the boat in.
Good Luck!

 

[Cobra Jet Steering LLC]

Here is a trick I learned years ago before a lot of you folks were even born and it still works . When installing stainless bolts through aluminum especially if you run in salt water coat the bolts with bees wax, water has no effect on it and it is very inexpensive. I always coated my impeller in the lower units of my outboard engines with it to prevent the impeller from wearing down at slow speeds , years later you could still feel the wax on the water pump impeller. Newer fixes for the pump liners as for avoiding the dissimilar metal corrosion of the pump liners I replace them with the newer pump liner sections that use the nylon liners having great luck with them and no more noise in the pump and the liners are replaceable. Also in salt water add zinc anodes to your pumps.

 

[Dan Ruehl]

Same issue…did you find the correct tap?

M10x1.25