1985 40hp evinrude only runs at half speed - Light Outboard Motor Boat Bass Fishing Saltwater Base

Hey Pete.. this sounds serious.... will it rev up while in neutral? If it revs freely and high.. the power head should be ok.. if it will NOT rev up freely and high.. STOP - you are causing more damage..
Check the compression with a good gauge..it should be 125psi minimum.. with no more than 10 psi difference between any two cylinders.. DO this WITH the THROTTLE WIDE OPEN...
Can you turn the propeller by hand while it is in neutral?..Of not.. this is the problem.
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90 hp 1993 evinrude idle speed - MarineEngine

www.marineengine.com > ... > Johnson Evinrude Outboard Archive

Aug 3, 2008 - 2 posts - ‎2 authors
"How many rpm should the engine idle at,and where and how do you adjust it Thanks" 50 hp evinrude no idle and no top speed need assistance ...
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adjust carburators and idle speed 1993 48hp
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1993 Johnson 90-HP Runs Only At Idle Speed On Spring Start-Up

Johnson 1993 115 xflow Link and Sync - YouTube? 4:55https://www.youtube.com/watch?v=ReeuaVh8uZQNov 25, 2012 - Uploaded by Brian O'DellJohnson 1993 115 xflow Link and Sync. Brian O' ... Also if you can give me some details on how you got the ...DOWNLOAD Evinrude 90HP (90 HP) Repair Manual

Bad gas is one thing, 2nd may be dirt in carbs, 3rd fuel filter etc. May cracks in prime bulb. Lot of little things happen when set for some time w/o running. good luck

Check the fuel tank for water.Squeeze the fuel line bulb and see if that gives a boost,and if it does you may have a blockage in the tank or in the carbs.If the bulb contracts when the engine is running,you have a blocked pickup in the tank.Check the vent on the tank is not blocked.The symptoms you give all lead to a fuel problem.Also.Check to plugs after you have run the motor.If one looks darker than the other.Change them both.Hope some of this may help you

You should have a High Speed carb adjust and a Low Speed carb adjust. If it's running fine while idling, adjust the high speed setting. If you have two nobs, its the lower one. May be set wrong. If you don't have two nobs, remove the carburator and check the jets to make sure they are completely clean or better yet, order yourself a carb rebuild kit to take care of all of this. I just rebuilt my 1971 evinrude 4hp and the carb kit made the world of difference.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/matthew_d24b835e574ef6ca

You can get rpm data by searching your browser using "90hp Evinrude Specs" or "1982 90hp Evinrude idle specs". Changing the jets usually costs you performance on one end or the other. If you have needle rods, a narrower one will have the same effect as a bigger opening in a jet. But you have rpm limits that you should not exceed. Changing the prop can give you more power over the sacrifice of top end speed.

Check out the online info on this site, or on the search window type in 40 hp evinrude wiring diagram and go from there.

Sound like the fuel pump is not keeping up with the engine's demand. Check it out. Good luck. Hope this helps.