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Senior Contributor

Mercury Optimax outboard ?

I have a 90 HP Merc optimax on my fishing boat, have any of you changed the water pump. I think you take the bottom four bolts off and it comes out but dont know, its my next rainy day problem. It wasnt hardly spitting at all the last time I had it out. But moron alarm didnt sound.

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j1942p
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Re: Mercury Optimax outboard ?

I have a 115 Merc @ '95 vintgage.  Twice in the last 7 years it either barely dribbled or didn't dribble any cooling water out the P hole.  My cure has been to get at least 60 lbs of air pressure blown backward (into the P hole and out the water intake down in the lower unit.)  Had to do this last June at dockside after running the boat through some shallow water with a lot of weeds, etc.    Apparently the intake will pull in underwater weeds and eventually plug up the cooling system.  

Got this "tip" 7 years ago from a mechanic at the locat Mercury marina dealership who said this back-blow is the first thing they do with a suspected maifunctioning waterpump.

Both times after the back-blow, water came out the P hole like a 10 year old boy instead of an 80 year old man.  

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