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1978 260HP Mercruiser impeller Question

S

SUPERNUKES

New member
My 1978 Convincer with the 5.7 260 mercruiser runs too hot. I finally got brave enough to drop the lower gearcase to change the upper water pump and impeller. The old impeller has curved blades but the new Quicksilver replacement has straight blades. Did Mercury change from curved or do I have the wrong impeller. I cannot find a serial # on my sterndrive. All the impellers I've seen for sale have straight blades. Also any tips or areas of concern rebuilding the upper water pump would be appreciated. Thanx
 
My 1978 Convincer with the 5.7 260 mercruiser runs too hot. I finally got brave enough to drop the lower gearcase to change the upper water pump and impeller. The old impeller has curved blades but the new Quicksilver replacement has straight blades. Did Mercury change from curved or do I have the wrong impeller. I cannot find a serial # on my sterndrive. All the impellers I've seen for sale have straight blades. Also any tips or areas of concern rebuilding the upper water pump would be appreciated. Thanx
 
The blades on a new impeller are straight.

The part#, from mercury, for your impeller is 47-89984 4. The blades take a set over time. This is what has happened to yours. My rule of thumb on impellers is not to use them longer than 5 years. It is also important to note the condition of the plastic housings. If they appear to be melted replace everything as a kit.

I'm not sure what you mean by the upper water pump? The one on the engine?

One thing that you should also check is the water house that runs between the gimble house and the transom plate (5/8" hiose about 12" long) They have a tendancy to crack over time. I'm not sure how often you do it but you should regularly service the u-joints and check the bellows condition as well.

Hope this helps.
 
5 years on an impeller
icon_eek.gif
I never went more than 1 year.
 
Vinnie,

I boat in the fresh waters of Canada, no salt, no silt, no acid content. I've probably changed 500 impellers in my life. We can get that here. That's why I said "My rule of thumb on impellers is not to use them longer than 5 years" Emphasis on longer than. Conditions in your area must be pretty harsh if you can only get a year from an impeller.
 
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