1973 Merc 7.5hp

C

contrldsub

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first off this is my first boat. i know motors very well but i dont know the works on a outboard that makes it go. so heres my question: after running it for about 15 minutes when i slow down and just put along i get steam from the water output tube. a higher RPMs there is water but it feels warm to the touch. after i slowed down and the steam started i got going faster again and the water began coming out once again but it seemed uncomfortably warm. is this normal or do i need to do something with the prop shaft?
 
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Laddies

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Re: 1973 Merc 7.5hp

The impeller has a set in it and needs to be replaced. If you keep running it you will ruin the engine.
 
Wingedwheel

Wingedwheel

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Re: 1973 Merc 7.5hp

What Laddies said. Its an easy fix and not too expensive or hard especially if you are good with mechanics.
 
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contrldsub

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Re: 1973 Merc 7.5hp

a set? not familiar with the term. please explain. thank you or the help.
 
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Laddies

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Re: 1973 Merc 7.5hp

The pump works on a eccentric, at idle it is a positive displacement pump and at higher speeds is a slinger pump. A set is when the blades of the impeller get bent over from old age and do not wipe the pump housing to pump at slow speeds but as the RPM go higher the slinger takes over and it will pump.
 
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contrldsub

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Re: 1973 Merc 7.5hp

ah now that makes sense to me so your saying that i need to replace the impeller at the bottom of the shaft. that dont sound to bad at all. thanks. i even found out that the local mercury place has one in stock so i am going to pull it apart this evening and see what else it might need.
 
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