Need some serious help with my 1993 20hp 2stroke merc

[boater1234]

Ok,so here is my issue.I go to the lake today and my outboard runs great at idle,got all the tuning great and here we go to wot and 15 seconds later it stalls.To make a long story short because i'm so frustrated and i'm hoping someone else has had a similar issue so i can get help.Here is my issue.When i go wot it wants to stall unless i constantly keep pumping the bulb and then it never stalls out.I tried 2 different new lines and tanks and got the same issue.It runs like a raped ape but it won't stay going unless i constantly keep pumping the ball.I have replaced all the gaskets in the carb,the carb is in mint with no varnish or old parts except there is a plastic fuel pump that is obsolete and a spring release valve that i can get but only in a repair kit for $90.Now i don't mind spending the money but i just don't know if that's the issue.Everything fuel related is brand new on this outboard including the tank and line.

I went to my local marina and they couldn't even answer me and tell me a round about what it could be but that release spring valve that i guess acts as a vacuum to suck the gas in,The lady i know well there said if the plastic part was bad it would leak gas.So i ask for any help please because i love this outboard and i don't know what to do as of now.I don't know what else it could be.

 

[Afishinday2me]

I'm not an expert but it sounds like it's not getting enough fuel. You may have tried most of this but here's a rundown. I would first check to make sure that the fuel connections to the tank and to the motor are not leaking/pulling in air. Then check the all other fuel lines for leaks. Did the the new fuel line come with connectors and fuel bulb? Next make sure that the vent on the tank is open to prevent a vacuum effect. Clean/replace the fuel filter as it may be clogging up at WOT. Pull the fuel line off of the carb and lightly pump the ball to see if there is any fuel restrictions. This is not likely but Check to make sure that the carb is secure to the block(No cracks or loose nuts)and is not pulling in air from behind the venturi. Last there is always the possibility that the fuel pump is going bad. Hopes this helps and there a lot good mechanics on here that may chime in and pin point it for you.

 

[boater1234]

Problem is i can't find a fuel pump,it's obsolete.Do you know how frustrating this is.I ran near 30 minutes wot straight but i had to keep priming the ball every couple seconds.Believe me when i tell you the fuel lines are spic and span,all new hoses,new fuel filter assembly,plugs,coils,wires,complete water pump redo,not just the impeller, i did it all,new synthetic lower unit oil,new fuel tank and line(mercury),redid every gasket on the carb,New thermostat,new gasket to,new pee hose from thermostat to were it pees,new female fuel fitting on the engine, i have done a ton of work to it and now it won't run right.

 

[flyingscott]

Problem is i can't find a fuel pump,it's obsolete.Do you know how frustrating this is.I ran near 30 minutes wot straight but i had to keep priming the ball every couple seconds.Believe me when i tell you the fuel lines are **** and span,all new hoses,new fuel filter assembly,plugs,coils,wires,complete water pump redo,not just the impeller, i did it all,new synthetic lower unit oil,new fuel tank and line(mercury),redid every gasket on the carb,New thermostat,new gasket to,new pee hose from thermostat to were it pees,new female fuel fitting on the engine, i have done a ton of work to it and now it won't run right.

The pump is NOT obsolete it is part of the carb. Get the carb rebuild kit and it will have the fuel pump kit in it. Try this kit 1395-9761 1 the plastic spacer in the pump gets reused. How did you redo every gasket on the carb and not do the fuel pump or the plastic primer. Give a serial#.

 

[boater1234]

The plastic spacer is obsolete, i can not find it anywhere.I replaced every gasket on the carb.I got a diaphragm kit,not a repair kit.Could the plastic spacer be the issue?Plus it has like a valve spring which seems to operate perfect as well.The only thing in the repair kit is the valve spring along with all the other parts but the fuel pump plastic body itself is not,no plastic fuel pump body.I wanted to replace that but i can't find it anywhere even on ebay.All the fuel lines are brand new.

I am wondering if the new male fuel connector on the engine which is brand new as well is not letting fuel in unless i force it in.Also when my buddy took the end connected to the fuel tank off because it was his fuel line i tried after my brand new one as well,he used his finger to press in the little valve at the end of the fuel line to drain what was left in the outboard because he has a 4stroke and we needed to clean the 2 stroke gas out and it was spitting gas back out of the end almost in his face,basically the engine was spitting gas back out instead of sucking it in all the time,he found that odd as i did to. he has a brand new tohatsu and drained his line and it didn't do that at all,all the gas went into his engine and his line drained easy,my engine did some crazy stuff.

 

[boater1234]

serial # is 0D202003

 

[boater1234]

The number you gave me is the carb gasket diaphragm kit which is what i got and installed on the engine just a month ago,there is no fuel pump in there but there is the diaphragm that gets installed on the fuel pump which is bran new like i said and the gasket behind the plastic part.Is there anything on the plastic part itself that can go bad besides the check valve spring which causes suction vacuum to suck engine into the carb fuel pump>The check valve seems operational to,looks like it works well. Maybe i will buy a complete repair kit which has a bit more stuff in it and install everything.I replaced the needle,the float was perfect as well as the hinge,the carb itself was clean as a whistle so like i said this is so frustrating.

 

[boater1234]

This is extremely frustrating and it would be pointless to bring it to a repair place and get hammered with a bill that probably won't fix it as my local marina told me.I guess it's carb tearing down time again.Sometimes the ball gets hard and stays hard for a few minutes then it's like after minutes of idling in the driveway now it in time stalls and it's extremely hard to start up again and i do notice when pumping fuel in to the fuel filter it stays full all the time,just the ball seems to lose pressure and it seems like air is sucking somewhere.What in the carb itself could do this if any,like the needle,float,jets,anything so i can check it.

 

[boater1234]

Holy molly, i just realized my post got posted 3 times and i don't know how that happened and i can't delete 2 of them,sorry.

 

[boater1234]

I'm wondering if it's a stuck needle because we took my buddy's gas line off and gravity fed the fuel in the line to my engine and it was spitting gas back out the fuel fitting that came off the gas tank while I was sti king my finger on the peace that let's gas in. That tells me it was refusing gas while running.

 

[Chinewalker]

Do you have one of those new tanks with the vent that won't vent? EPA has made the new tanks somewhat problematic with their efforts to reduce emissions of unburned fuel. Sometimes the vents don't let in enough air to allow for the gas that's getting pumped into the engine. Maybe try running the motor with the gas cap loose?

 

[boater1234]

Well here is what I know,my buddy's 20hp 4stroke Tohatsu line and tank works on his brand new outboard so if it works on his shouldn't it work on mine as well?

 

[boater1234]

If I constantly keep pumping the primer ball the engine will run and run,then I let off the primer ball and it stalls in seconds,I push gas in again and she goes but only by constantly pumping the ball.

 

[Silvertip]

Having to continually pump the primer ball is a classic symptom of a bad fuel pump. And just so you know, the primer ball does not stay firm after the engine starts because fuel is now being drawn through it rather than forced. You need to bite the bullet and fix the pump or look at a work-around fix using a non-pump type carb and external fuel pump (not an electric).

 

[flyingscott]

VERY seldom does the plastic piece get replaced. I have rebuilt about 100 of those and never replaced the plastic body. The only way that will go bad is if you over tightend everything and cracked it.

 

[boater1234]

I replaced all the gaskets on the carb with a new carb diaphragm kit,the only thing i can think of is the gasket where the valve spring operates to suck gas in has a pin hole leak or the spring valve itself is not working right but it seems operational(the spring that is).The only other thing i can think it to be is a stuck needle.

 

[boater1234]

It just starting raining here so when it quits i will pull the fuel pump apart and take a flashlight to see if i can see light through the gasket,I have the old gasket that came off also i may reinstall to see if maybe the new one is defective.The old gasket is in great shape to.

 

[boater1234]

UPDATE FIXED:::::::::::You will never believe what it was, i put the wrong gasket from the carb to the power head on,i must of noticed this when i was working but i was doing like 10 things at once when i was working on the outboard and must of got side tracked and forgot to replace it with the right one in the carb kit and the right gasket fit the same but the wrong one was covering one of the holes that ran into the engine starving it for fuel,i'm a complete dummy,lol. Honest mistake and now it runs like a sewing machine.Man i can't believe after doing so many different things to it,it was such a simple fix,runs awesome now. Thanks for all the help and i'm sorry for my mistake.

 

[boater1234]

At wot she runs 28.3mph with 1000lbs total weight running in a 1648 flat bottom jon boat,imho that is as impressive as it gets for a 20hp. I raced my buddy's boat which is also the same boat with a 20hp 4stroke Tohatsu on it and I was more impressed with the torque of his motor than anything,it was how fast he planned (under 2 seconds)with the same boat. He was running a 10 pitch prop and I was running a 13 pitch prop both standard that came with the engines. He smoked us off the line but I quickly caught him in seconds and even passed him which I'm sure him beating us off the line had to do with his prop being much smaller giving him way better torque which was impressive anyway u look at it. If he ran a 11 pitch prop it may run a bit faster but lose a bit of torque off the line but I wouldn't think much. He hit 24.7mph with near 800 lbs in the boat give or take a bit,with just him he hit 27mph. I never did a wot run in my boat with just me due to the issues I was having, tom morning I'm going to the lake and I'm going to see what kind of wot I get with just me in the boat,I'm hoping near 30mph or better,that would be plenty fast.