Evinrude 1986 90hp power problem?

Question

Hi all,

The engine starts and runs well right through the rev range for about 20mins and then looses power and won't rev much over about 2000rpm. I've found if I activate the electric choke by pushing the key into the ignition I get full power back, this suggests its a lack of fuel problem. The VRO unit is removed, running a new diaphram fuel pump off the crank case. Am I best to remove and rebuild carby's? the manual suggests carby's are rarely the problem and adjusting can cause more problems... is it worth using an injector cleaner or spraying carby cleaner... what should I look for in carby's? blocked jets? any help appreciated, thanks

Answer 1

Which manual is telling you that carbs are rarely the problem?

Does this motor see regular use, or has it been sitting for a while?

On a 2 stroke, dirty carbs are often the cause of poor running conditions like you described.

-Is the primer bulb still hard when it starts loosing power?

-do you have a water seperator or other fuel filter that may be blocked?

-if  those items check out ok, it's time to disassemble and clean the carbs.

Dont waste your time or money with spray in carb cleaner.

Answer 2

Sounds like the carbs have either dirt or water in the bowls that gets to the primary jets after being churned up for a while.

Take the bowls off and look for any contaminants. Water is heavier than fuel so it will look like a blob under the fuel in the bowl. Remove and inspect all the jets, hold them up to a light and be sure you can see through them. Spray them with carb cleaner and blow dry if you have a compressor. If they have idle mixture screws count the number of turns when you remove them and return to that setting upon reassembly.  Injector cleaners are not recommended for these engines because they can thin the oil mixed with the fuel. Only disassemble 1 carb at a time to keep the jets with the carb they came from. If you find water drain and dry the tank.

Answer 3

Sounds like you have a blockage somewhere in the fuel system. Check your inline filter if so equipped or you may have some crud built up on the intake tube in your tank. I know you have done this but make sure the vent for the tank is open and also make sure that the vent is not blocked off some how.

I hope this helps and happy boating.