1990 25Hp Evinrude won't accelerate?

[Bone1099]

I have a 1990 25hp Evinrude that was given to me. Hung it on the boat opened the cowl and began my adventure. First let me start with all of th variables that i know. (Before I received it) It supposedly was running good then it was removed and stored for a while and then reinstalled. I am just guessing that it wasn't running very well at this point so someone was messing with it had the plugs out apparently reversed the fuel supply line and the primer pickup line (as this was how i found it) they were pulling the rope it was pumping the bowl overfull and out of the vent filling the compartment with fuel and (imagine that!!) caught it on fire. (Idiots!!) It appears that the fire wasn't very bad it only melted a few fuel lined and caused a bit of exterior damage to the primer housing. Seems that the worst of the damage was the small line out of the primer burned a bit and melted the plastic fitting closed on the end barb is still there. cleared the hole and the primer works. removed and opened the carb one side of the carb was full of Goo apparently engine was stored on its side. So i cleaned the carb all ports seemed to clean up pretty easily blew through all passages they checked good too thought to myself alright we're bout' ready to go reinstalled carb took it to the neighbors pond it started right up and idled reasonably well but it wouldn't accelerate so thought to myself main jet must be restricted. Repeat carb cleaning procedure removed main jet first and it was clear checked float level looks parallel to the body of carb. Needle seems to open ok. Reinstalled and returned to the pond Same problem although this time it will accelerate a bit and i can drive around the pond a bit but anything over 1/4 throttle seems to kill it I can manually choke it with my hand and it accelerates ok but manually finding that sweet spot with my hand while dirving circles in the pond and watch out for that dad-gum big rock over there in front of the pic-nic table that you cant' see but trust me it's there. I can manage to get almost full power for a few seconds at a time. think to myself ok ive' got trash so i remove it clean it and still to no avail. Sorry about the novel but i wanted to try and get you all the info I could. Any input is greatly appreciated.

 

[Rick.]

Re: 1990 25Hp Evinrude won't accelerate?

Did you replace all the fuel lines from the tank to the carb.? Is your tank vented properly? You could give it a try with the tank fuel filler removed (but be very careful about spillage) Have you tried pumping the bulb to see if it makes it go faster longer? Some one will have an answer I'm sue. Best of luck. Rick.

 

[Bone1099]

Re: 1990 25Hp Evinrude won't accelerate?

Yes I relpaced all fuel lines and pump bulb. Tank cap kinda sucks cuz it don't seal reel good but it does vent air in and gas out. Don't worry it is high on the list of stuff to replace but first i want to get the engine running better.

Pumping bulb while running doesn't help.
Primer does help but this is no good cuz the primer doesnt have anything to do with the carb it just gives a burst of power for a second.
The problem must be in the carb I keep thinking. It just seems that everything in the carb is good.
I haven't a lot of experience with marine carbs but I have rebuilt and tuned dozens of Motorcycle, ATV, and aircraft carbs. Only once have I had a carb i just couldn't get right on an ATV and then after replacing it I found the Pilot emulsifier tube was broken at the top and leaking air.
This just beats me

 

[Bone1099]

Re: 1990 25Hp Evinrude won't accelerate?

Today I will check for a vacuum leak around the base of the carb and around reed/rotary valve cover.

 

[Mas]

Re: 1990 25Hp Evinrude won't accelerate?

What do the plugs look like? Wet? Compression numbers?

It does sound like it's starving for fuel. Have you disassembled the fuel pump?...there could be a filter inside that's clogged.

MAS

 

[Bone1099]

Re: 1990 25Hp Evinrude won't accelerate?

More work today cleaned carb again added inline filter checked float level while running. fuel level remains pretty constant i do not think delivery to the carb is the problem. so I checked for vacuum leaks no apparent problems there. I keep telling myself there is no reason for someone to have changed the main jet but the tuner in me keeps saying that the main jet is too small. out of desperation I removed the main jet entirely (remember I am doing all of this on the neighbors pond) It ran much better but obviously rich. Before removing the jet looking into the carb while running the engine I could never see any fuel spray in the throat of the carb. After removing the jet I could see a nice spray of fuel into the throat. So I begin to believe this main jet has to be too small! The jet has 51D stamped on it. Does anyone know what the proper jet size is for a 1990 25Hp evinrude? My elevation here is about 650 ft above sea level. The engine has a South Carolina registration sticker on it so i doubt it has been tuned for high altitude.

 

[Bone1099]

Re: 1990 25Hp Evinrude won't accelerate?

I am a mechanic and i like to think i am a pretty good one. So I haven't taken this whole thing very lightly. So after driving my self nuts looking at the book I got online looking at evinrude website online parts diagram of the carb and staring at the parts catalog and reading the text and staring back at the parts diagram it hit me right there in black and white nozzle gasket I didn't have one then I realized what would happen if it was missing. When the throttle is opened main fuel nozzle would suck air in over the top of the cast tube protruding from the bottom of the carb.

 

[tashasdaddy]

Re: 1990 25Hp Evinrude won't accelerate?

yep.