1980 Mercury 9.8hp outboard

[Juabarr]

I recently bought this outboard. It’s in mint condition. Was garage stored since 1986. Starts right up. Replaced water pump impeller which had shredded. Water from discharge tube is not a steady stream. Goes from steady stream to spitting. Runs warm then gets very warm/hot. Then seems to go back to warm again. Runs same with or without thermostat.

 

[tpenfield]

Probably some impeller bits went up into the cooling passages .

also if it had overheated, there is a plastic washer at the top of the copper intake tube that can melt. and restrict the water flow. Not sure when Merc changed to the phenolic material.