1990 90hp Johnson Outboard WOT Loses Power

lowcountryboil

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Here is the deal..........I boat this boat used from a guy and the boat had sat for two years.....It has ran great until the other day... Here is some background of what I have done before my question.....I filled the tank up once with 17 gals of premium fuel plus a bottle of Sea Foam and replaced all four plugs........boat has ran like a champ.......before taking out the last time I filled it up again with 14 gals of premium fuel and gum out fuel treatment that is supposed to remove water.......like i said this motor had ran like a champ for me on four other occasions........when I was pulling someone on a tube at WOT it lost power almost to idle but did not die......i backed off the throttle then tried to go WOT again and the motor regained some power but not much......decided to back off and pull into the sandbar.........we sat there for a couple of more hours and when we wanted to leave we could not get the motor to start........I have checked all fuel lines, filter, and primer bulb...all are fine.....not sure about the mechanical fuel pump though.........when checking the the fuel lines/bulb, etc...i noticed that the fuel coming out was somewhat tan in color so i squirted into a clear plastic bottle.......there was separation at about 40% fuel/oil mix and the bottom 60% was a brownish liquid which I assume is dirty water.......I do not have a fuel/water seperator yet..........talking with people about this some think that my thermostats are bad and need replaced....does anyone have an explanation?.........remember i could not get it started but havent tried since.........thanks
 

Solittle

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Re: 1990 90hp Johnson Outboard WOT Loses Power

Simple - - you said "separation at about 40% fuel/oil mix and the bottom 60% was a brownish liquid which I assume is dirty water."

1. You need to get ALL of the water & crud out of the tank.

2. Rebuild the carbs & install a fuel filter/water separator.

3. Use 87 octane fuel not premium.
 

boobie

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Nov 5, 2009
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Re: 1990 90hp Johnson Outboard WOT Loses Power

Also check your fuel tank fill cap so no water is getting in.
 

lowcountryboil

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Re: 1990 90hp Johnson Outboard WOT Loses Power

what would be wrong with the carb that it would need to be rebuilt.......also, everyone that i have talked to that has boats and uses them regularly says to put premium fuel in.....why do you say to not use premium?
 

emdsapmgr

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Dec 9, 2005
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11,551
Re: 1990 90hp Johnson Outboard WOT Loses Power

It does not need premium fuel. Check your owner's manual. Your engine is rated by the factory to run on 87 octane. You are wasting your $ on premium.
 
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