Water Passages

I have an older early '90s NS-5 two stroke. Last season I was constantly having to clean the telltale to keep it streaming. The motor is run in brackish water most of the time and flushed as a part of closing up each weekend. I was thinking about turning the engine upside down and filling the cooling passages with Lime Away through the flush port in an attempt to break up any scale that has formed over the years. Would let it sit for 30 minutes or so and then flush well. Good idea? Bad idea?

 

This could also be that the pump impeller is finished
Install a new impeller anyway

 

The impeller was new last season. It pumps plenty of water. On the sailboat the HX gets boiled or rodded every few years to clear the scale, just wondering if the outboard needs a similar cleaning and if there is anything in there that the Limeaway might harm. Thermostat or similiar. Can't find a decent diagram of the cooling system.

 

They are aluminum engines. Limeaway will erode a lot of metal off.

 

Thanks Gonzo. After you posted I started looking on line. Limeaway is not recommended on most metals. CLR perhaps, on line isn't clear, will have to read the back of a bottle at the store. Google recommends soaking in a warm mixture of water, vinegar, lemon juice and a tbsp or two of Cream of Tarter to remove scale. I think I'll give that a try.

 

Most engines have inspection plates for the water jackets. If you can remove them, wire brushes can take most of the deposits away.