93 Mercury 20 HP dies

[BYBUTTERS]

FINAL POST... Success...finally. Thanks to all for their advice and help. It was a stuck float in the carb and the engine loaded up with fuel and killed her when opening the throttle. But, I found a way to clean the inside of the carb without taking it all apart and rebuilding it. Pulled the fuel line off where it enters the carb and started the engine and burned the gas out of the carb. Then filled the carb via the fitting where the gas line came off of with Gum-Out carb cleaner and let it soak and bubble for a few minutes. Reconnected the fuel line and started the engine. That's all it took. Ran around the lake like a kid with a new toy. By the way, even though this is a 1993 model, it has less than 50 hours on it so I didn't think the fuel pump diaphragm could be bad.

20 HP Merc on pontoon... new gas in tank... new gasoline & bulb but using old fittings to external tank and motor. Starts good, idles good.. but will not rev.. when you open the throttle either fast or slow engine dies. Will restart OK. Can fast idle with cold start lever. Put seafoam in tank. No change yet. It must either be something plugged or an air leak. Don't know what to try.

Help.

Add'l - "gonealong" describes the problem better than I. I have now run engine medium fast idle and sprayed puffs of Gumout Carb cleaner into the carb throat. Changed spark plugs also. I can tie up at dock and put in gear and get maybe 1/3 throttle before it dies out. There is no rough running... it just dies. I haven't dared tackle taking the carb off yet. Last resort for me.

Byron

 

[Barnacle_Bill]

Re: 93 Mercury 20 HP dies

Make sure your tank vent is open all the way. Its normal for the bulb to go soft when the motor is running but shouldn't get sucked flat.

 

[tashasdaddy]

Re: 93 Mercury 20 HP dies

sound like dirty carbs.

 

[BYBUTTERS]

Re: 93 Mercury 20 HP dies

Vent is open... bulb does not get sucked flat. Dirty carb... like jets being plugged or something. What do I do... use chemical cleaners in gas or take carb off and try to clean?

Byron

 

[Windykid]

Re: 93 Mercury 20 HP dies

How long has that motor set still?

 

[tashasdaddy]

Re: 93 Mercury 20 HP dies

remove disassemble, soak and cleen till shiny, all inlets and jets, reassemble with a rebuild kit. not the turns on the jets. count the number of turns in until seated lightly, and record, so they can be set back. after starting they can be adjusted. maybe.

 

[Windykid]

Re: 93 Mercury 20 HP dies

Agree with TD, but make sure you blow out the ports and passages with compressed air. I have seen all kinds of critters make a home in the smallest places.

 

[BYBUTTERS]

Re: 93 Mercury 20 HP dies

How long has that motor set still?

2 Years.

 

[BYBUTTERS]

Re: 93 Mercury 20 HP dies

Since I never done this before.. should I try to find a manual or instructions before I try?

Byron

 

[Harker]

Re: 93 Mercury 20 HP dies

I would suggest finding a manual..the carb rebuild isn't that tuff but a manual will help you with other stuff and is good reading if you want your motor to last. I'd get some new spark plugs too.

 

[gonelong]

Re: 93 Mercury 20 HP dies

20 HP Merc on pontoon... new gas in tank... new gasline & bulb but using old fittings to external tank and motor. Starts good, idles good.. but will not rev.. when you open the throttle either fast or slow engine dies. Will restart OK. After idling for a while bulb hardness is gone. Put seafoam in tank and ran for about 1/2 hour with no change yet. It must either be something plugged or an air leak. Don't know what to try.

Help.

Byron

I have the very same problem with my 76' 50 HP Merc so I'll tack it on to yours. Maybe we can help each other out.

* New Gas Tank (tried, open, closed, partially vented)
* New Gas at 50:1 Mix
* Firm Bulb
* Motor Starts easily (with choke), idles nicely
* Use lever to rev motor up a bit, warm up (runs nicely)
* Drop into gear and it dies right away.

* Starts back up easily
* Can put it into gear with little to no throttle and use the lever to get the boat
moving (no wake), but if I use the gear-shift throttle at all, it dies.

* If I keep it out of gear, I can use the seperate throttle leve to rev the motor up pretty well (maybe 1500-2000 RPM?)
* If I shift into gear and try the lever, maybe get a few hundred RPM out of it max.

I have a manual I can refer to, though I haven't specifically looked at the Carb information either. I am assuming I'll get the same response as BYBUTTERS ..

remove disassemble, soak and cleen till shiny, all inlets and jets, reassemble with a rebuild kit. note the turns on the jets. count the number of turns in until seated lightly, and record, so they can be set back. after starting they can be adjusted. maybe.

make sure you blow out the ports and passages with compressed air.

GL

 

[Harker]

Re: 93 Mercury 20 HP dies

I'd check all the wiring and linkage where it moves to be sure something isn't getting shorted out and the kill wiring in the control to make sure it isn't rubbed bare.

 

[hammyloz]

Re: 93 Mercury 20 HP dies

i had exactly the same problem so i got new tank new bulb new lines new spark plugs cleaned carbs out got very frustrated it turned out to be the fuel diaphram

 

[gonelong]

Re: 93 Mercury 20 HP dies

I check the wiring, not a problem there.

As I took of the cowling this evening I noticed that there is a control to open the carbs manually. I'd assume that this is for a mechanic to manually control this in conjuction with the throttle to check timing, etc.

Here is a picture of it, circled in red.

The knob/control had the carbs wide open. I'd have to think that they should be completely closed or at least mostly closed to begin with. Any advice on the setting of this would be appreciated.

I think this would explain how it would just choke out when I tried to give it any throttle.

Thoughts or advice?

Thanks,

GL

 

[Jugfisher]

Re: 93 Mercury 20 HP dies

I wouldnt rule out your pistons. You can get the same problem if your pistons arn't putting out the right amount of compression. Check to make sure if they are. I am not sure the proper pounds of pressure you should be getting. I think it is around 115. You may want to ask around to be sure. All of them should be hitting just bout the same mark.

 

[gonelong]

Re: 93 Mercury 20 HP dies

After some thought it occured to me the control is a manual choke, most likely for use in pull-starting the engine.

One of my buddies has a tool to check compression, I'll get with him and check it out. I really doubt that is the issue as my neighbor at the lake owned this boat and his boy ran it around for a few years without issue. It did sit for about 18 months so I suspect that has something to do with my issues.

GL

 

[hammyloz]

Re: 93 Mercury 20 HP dies

did you manage to sort out youir problem

 

[BYBUTTERS]

Re: 93 Mercury 20 HP dies

Update.... problem not gone yet. Haven't got brave enough to rebuild the carb but mixed 2 cans Seafoam to 5 gals of gas and been running engine off & on the last few evenings. Last nite put in gear tied up at dock and seemed like I got more rpm, possibly 1/3 throttle or so before dying out. Maybe the Seafoam is opening the pin holes little by little. I'll run the entire tank out and see.

Byron

 

[gonelong]

Re: 93 Mercury 20 HP dies

Good Luck Byron.

I think I am going to try to clean things out with seafoam as well. I know it'll be some time before I can dedicate a Saturday to rebuilding the carbs. I am hoping to be able to run some Seafoam through and at least see some progress.

Questions about seafoam for the forum. I have spent an hour or so searching/reading the forum but haven't found an answer to the following questions ...

1) Is there any harm in running seafoam in your gas on a regular basis (all the time?)

2) Is there any issue with having it be weeks or months between engine use and having seafoam in your tank sitting that long? If not ...

3) Is there any reason the seafoam shouldn't sit in the tank over the winter? If not ...

4) Is there any reason not to put stabilize in your tank with the seafoam sitting in it?

The reason I ask is that at the 2-3 places I generally fish ... 1 of them only allows electric motors to be run, and the other two I usually fish right at the docs, I don't even need to start the motor.

I plan to run the motor pretty much every chance I get, just to keep it active ... but it wouldn't be unusual for it to sit for a month.

Thanks,

GL

 

[j442w30]

Re: 93 Mercury 20 HP dies

Good Luck Byron.

I think I am going to try to clean things out with seafoam as well. I know it'll be some time before I can dedicate a Saturday to rebuilding the carbs. I am hoping to be able to run some Seafoam through and at least see some progress.

Questions about seafoam for the forum. I have spent an hour or so searching/reading the forum but haven't found an answer to the following questions ...

1) Is there any harm in running seafoam in your gas on a regular basis (all the time?)

2) Is there any issue with having it be weeks or months between engine use and having seafoam in your tank sitting that long? If not ...

3) Is there any reason the seafoam shouldn't sit in the tank over the winter? If not ...

4) Is there any reason not to put stabilize in your tank with the seafoam sitting in it?

The reason I ask is that at the 2-3 places I generally fish ... 1 of them only allows electric motors to be run, and the other two I usually fish right at the docs, I don't even need to start the motor.

I plan to run the motor pretty much every chance I get, just to keep it active ... but it wouldn't be unusual for it to sit for a month.

Thanks,

GL

1. No harm in running seafoam all of the time, on the contrary I and most of the others on this board would recommend it.

2. If you let your engine sit for long periods of time between uses, make sure you have a fuel stabilizer in the gas or your carbs are going to gum up. Seafoam also acts as a fuel stabilizer so no problem there.

3. Seafoam will keep the fuel fresh during the winter.

4. No need to add stabilizer if Seafoam is already in the tank.

As you can see, Seafoam is a wonderful product and I would recommend using it wholeheartedly, not just in outboards, anything with an engine.