Preparing / cleaning lower unit mating service after impeller removal - 5hp 2 stroke

[Jim2026]

Hi all,
Replacing the water pump housing and impeller on an early 90s 2 stroke Mariner 5hp.
The gaskets were well and truly welded on and took some effort to clean off, I ended up using some very very fine grit sand paper to fully clean up the surface - see pic. It’s cleaner than this now. Any pitting marks weren’t caused by me and were already there.

Having watched some videos, I’m now questioning whether I should have used any kind of sandpaper but what’s done is done.

Question - should I now use any kind of paint, protection or coating on these surfaces prior to reassembly? New gasket set, new pump housing, and the plate is also spotless with a light sanding.
The engine was previously used in fresh water and as you can see, was very clean inside but will now be going into salt water.
Bonus Q - anyone know the torque specs for the water pump housing bolts and the lower unit bolts?

Thank you.

 

[Texasmark]

Hi all,
Replacing the water pump housing and impeller on an early 90s 2 stroke Mariner 5hp.
The gaskets were well and truly welded on and took some effort to clean off, I ended up using some very very fine grit sand paper to fully clean up the surface - see pic. It’s cleaner than this now. Any pitting marks weren’t caused by me and were already there.

Having watched some videos, I’m now questioning whether I should have used any kind of sandpaper but what’s done is done.

Question - should I now use any kind of paint, protection or coating on these surfaces prior to reassembly? New gasket set, new pump housing, and the plate is also spotless with a light sanding.
The engine was previously used in fresh water and as you can see, was very clean inside but will now be going into salt water.
Bonus Q - anyone know the torque specs for the water pump housing bolts and the lower unit bolts?

Thank you.

Having broken (snapped) bolts and ripped out threads on fasteners when I was a teenager and starting out on my association with fasteners, I haven't had any problems since then. I started to pay attention to what I was working on and whether it was a shallow, small (1/8") diameter thread in plastic or a 5/16" stud/nut in stainless steel.

On fasteners on my pump housings and LU to Mid-section fasteners, I use a screw driver handled socket or screwdriver depending on the shape of the fasteners....forget what you call them on the pump housing.....you can't strip anything out with a tool like that, and on the SS bolt-stud/nuts holding the LU to the Mid-section a 6" open end wrench....both good and "hand" tight. Never had a problem.

On worrying about what I see in the picture, I wouldn't and if you are worried, every couple of years change the impeller. When you put the cover on the water pump, ensure that you installed the "key" that fits in the impeller to lock it to the drive shaft and then when replacing the cover, soap up the impeller blades (make them slick) and looking down from the tip of the drive shaft, LU standing up on the floor, clockwise rotation of the drive shaft a you put pressure on top of the water pump housing and the rubber blades will fold back and easily move into the top cover.

If you never dropped a LU before ensure that the shifter position on the LU corresponds to the position of your shifter lever (where you put your hand) and if the LU will go "almost" all the way into the mid section, the splines on your drive shaft and engine crank shift aren't lining up...move one or the other as you apply reasonable pressure to the LU and when they line up it will slide on up. Also put some grease on the threads of the shaft where it mates to the crankshaft but none on the end/top of the shaft. Grease on the end "can" prevent full engagement and no grease on the threads will just make it harder to separate the two sections the next time you pull the LU.