Deep pitting inside water jacket on power head.

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kalebsheridan

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Hey y'all,

I took the head cover off my 5hp mariner (this model has no head, just a plate covering the water jacket over the head) to check for sand and salt buildup and clean a bit. I noticed some deep pitting eating it's way towards the outside of the power head (on the outside wall, not the cylinder wall). By the feel of it, it seems like its getting close to popping through in places. Any fix ideas? If a hole ate through, I would have to replace the power head, which would be too expensive for this old motor to be justified. Any ideas would be awesome.

Thanks
 
M

Mc Tool

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1st thing I would check is the state and mounting integrity of any sacrificial anodes that may be inside the water jacket . 🙂
 
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kalebsheridan

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Chris1956 said:
You can epoxy the pitted areas. If you clean the metal, wipe it with acetone and use Marine-Tex to fill the pits, it will add some time to the block.
Click to expand...
Okay cool, definitely going to do that. Do I need to get down to bare metal or is patina okay?
 
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Chris1956

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Bare metal is best, however, it will oxidize some before you can apply the epoxy. Use a fine sanding or dremel tool to clean it up. Wipe with acetone and then immediately mix and apply the marine-Tex.

Some years ago, I did this repair on the inner water jacket cover of a Merc 4 cylinder OB, and it lasted as long as the motor did.
 
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kalebsheridan

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Chris1956 said:
Bare metal is best, however, it will oxidize some before you can apply the epoxy. Use a fine sanding or dremel tool to clean it up. Wipe with acetone and then immediately mix and apply the marine-Tex.

Some years ago, I did this repair on the inner water jacket cover of a Merc 4 cylinder OB, and it lasted as long as the motor did.
Click to expand...
Awesome I'll try that. Anything that can be done to prevent further pitting or corrosion? I thought the anodes where supposed to prevent that?
 
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Chris1956

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Whereas Yamaha has several anodes in the engine, I never saw the same in a Merc. Mercs have their anodes on the transom bracket and gearcase.

Of course, Yammies have a habit of their cylinder heads rotting out, so that may be the reason for all the anodes.

The other good news is that most Mercs have steel cylinder liners. These tend to hold up pretty well. You could also fix any rotted areas from the outside if needed.

Can you flush that motor after use in saltwater?
 
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kalebsheridan

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Chris1956 said:
Whereas Yamaha has several anodes in the engine, I never saw the same in a Merc. Mercs have their anodes on the transom bracket and gearcase.

Of course, Yammies have a habit of their cylinder heads rotting out, so that may be the reason for all the anodes.

The other good news is that most Mercs have steel cylinder liners. These tend to hold up pretty well. You could also fix any rotted areas from the outside if needed.

Can you flush that motor after use in saltwater?
Click to expand...
Very interesting. This is actually a Yamaha built mariner, so kinda confusing. I'll look more on the block for an anode but I'm not aware of any. I do flush it when I use it in salt water, but I mostly use it in fresh water. The previous owner clearly used it in saltwater, that motor lived in Seattle for a long time. I assume more of the corrosion happened before I got my hands on this motor.
 
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Mc Tool

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You could see if there is room ...maybe under the exhaust cover to put an anode in the water jacket .
 
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