20 HP Mercury with Fuel issue, Please Help

[cwattsx5]

I's a 20 HP mercury 200 outboard. I think it is around a 1972 model. the S/N # 2888354.
When I received the motor I had reason to beleive it had not been started in at least six years. I have been following this form and working on it for the past month. This is what I have done.

I checked the compression on both cylinders and they are the same (90 lbs)
I am getting spark in both of them.
I checked all wire for corosion and replaced what was needed.
Had the starter rebuilt.
Removed the carburator and took it apart, soaked it (to clean) and put it back togather. It had two needles in it. The Idle needle was turned to seat and backed out 3/4 of a turn. This carburator does not have the optional High speed needle, just a needle, gaslit and plug. I turned it in all the way because that is the way it came out. before install I blew into the carburator to make sure the flot was working. It works, no air passed when up side down.
When I tried to start the motor it turns over fine, that's all it did. I pulled the plugs and the gas does not seem to be getting to the cylinders.
I did not have the metal plate that goes in front of the carburator on it the second time I tried. I'm wondering if it is part of the grounding system and thats part of the problem or if i need to rebuild the fuel pump.
I did see some gas dripping from a rod at the bottom of the carburator.

I,m a first time newby, please if you have any suggestions pass them on.

 

[cadro68]

Re: 20 HP Mercury with Fuel issue, Please Help

I;m new too. I've fixed small engine (lawn mower) carbs but not a Merc one yet. One of the basics is making sure all internal stuff is clean and unobstructed. You might have a blocked orifice...gas getting in (leaking at bottom in your case) but not out of the bowl.

I'd get a kit and some pertinent maint. information...manual,tutorial video,etc and go through it thoroughly.

Did you do a search on it. Maybe one of the older hands will chime in.

 

[cwattsx5]

Re: 20 HP Mercury with Fuel issue, Please Help

Thanks for the reply, I took the carburator out and stripped it down. I put it in a can of carburator cleaner. I than blew it out with air and made sure that all the small tubes were clear. there were two needles, one I seated all the way inn ( the directions said that for the optional high speed needle I was to back it out 3/4 of a turn ) this one does not have that option. The other needle I did back out 3/4 0f a turn. I'm starting to wonder if I should have backed them both out.

 

[cadro68]

Re: 20 HP Mercury with Fuel issue, Please Help

You need some specific help/info it seems. Aside from that,there may be a blockage for no gas to get into the cylinders. I had that happen with a Tecumseh carb and there was a small hole that was clogged...even after blasting the inside with carb cleaner and canned air...I'd missed it initially.

I don't know why some threads get replies and others don't. Someone with experience with your particular carb could help,I'm sure.

Good luck.

 

[Mazey6]

Re: 20 HP Mercury with Fuel issue, Please Help

Hi,
have you had any results yet?
I to am having problems with the same engine serial number starting 299-- (which is a 1971). Engine wont start but sparking and i too have fuel dripping down the butterfly valve shaft.. this happens when i squeeze the primer bulb which must be then forcing the carb float downward allowing excess fuel into the carb. I've had carb off and completely cleaned. i'm being told that the problem is not with the engine but more likely the fuel... the 12 litre fuel tank had about 4 litres of fuel about 4 months old and i then topped it up with more fuel and oil mix. i'm being told the fuel will be 'bad' and i should have emptied out the original 4 litres before filling the tank. so i'll empty out existing fuel, fill with new and see what happens....

i will try this at the weekend and let you know how i get on.

 

[cwattsx5]

Re: 20 HP Mercury with Fuel issue, Please Help

I used a new gas and oil mixture with no results. I than sprayed some in the cylinders and tried to start it. still no results. This leads me to believe that my spark might not be good enough. Last time I checked it I received a pretty good shock from both plugs. Not to scientific. Do you have a reliably way to check the spark?

 

[Mazey6]

Re: 20 HP Mercury with Fuel issue, Please Help

Hi,
Still no luck for me. With fresh fuel, still wouldn't start. i've completely cleaned the carb and no jets are blocked. i've put a new diaphram in the pump. i managed to get it to fire for a fews seconds when i squirted fuel in the spark plug holes. it revved very high then just died and even repeating that it wouldn't start again. Plugs remain dry so no fuel getting through to it so i don't now if good or bad spark would make any difference. I now have a relation of mine looking at it as he's a qualified mechanic but mostly motor cycle engines 2 and 4 stroke, so he's going to check strength of spark etc.
don't know what your engine is like but mine is a sod to try and pull. now and again it will kick back and almost take your arm out of the socket!!
not giving up yet, until i get some feedback from my relation......

 

[starcraft1982]

Re: 20 HP Mercury with Fuel issue, Please Help

spark should jump at least a 7/16"gap.if it doesnt,its not stong enough.inspect your carb again for an overlooked obstruction,maybe run a small wire through the needle to clear out.might throw a fuel pump kit in also.then see where you are and report back.Also remember,old mercs need ALOT of fuel when cold.And another thing.recheck any/all wires.old mercs are notorious for rotting wires.since compression checks ok,you might want to just rewire everything.

 

[doryfishin]

Re: 20 HP Mercury with Fuel issue, Please Help

hi , i have a 1974 model , i had the same problem i put it down to someone making incorrect adjustments to the carb float . as it was wrong fuel would pour out the bottom . the measurement of the float drop should be 1/4" /mm holding the bowl cover in upright position . check out the needle make sure it moves freely on primary lever and doesnt stick . carefully bend secondary lever tab to get correct measurement . that is if your carb type is A for your motors year . hope this helps

 

[Mazey6]

Re: 20 HP Mercury with Fuel issue, Please Help

Hi Doryfishin,
are you saying that once you made this adjustment that when you now prime the fuel tank by pressing the bulb no fuel leaks out of the carb?

 

[doryfishin]

Re: 20 HP Mercury with Fuel issue, Please Help

hi , yes after adjusting the float and giving carb a good clean it solved the problem for me . with the float wrongly adjusted the fuel amount was too much for the bowl to handle therefore fuel being over flowed .

 

[Mazey6]

Re: 20 HP Mercury with Fuel issue, Please Help

The plastic cover plate (P/N 53545) on the fuel pump is split and therefore not working, hence no fuel to plugs. i can't source a new part anywhere as they are 'NLA'. Does anyone know where i can get a replacement part or is there a new pump or alternative pump i can use instead?

 

[cwattsx5]

Re: 20 HP Mercury with Fuel issue, Please Help

I checked the spark again and it looks good. After reading the last post I will take a harder look at the fule pump. Thanks for all the reply's. still, I did not get anything when I sprayed gas in the cylinders and tried to start it. I will check the spark gap as mentioned above. Thanks again and keep the post coming.

 

[Crazyman1225]

Re: 20 HP Mercury with Fuel issue, Please Help

If you are spraying gas into the carb and not getting ignition , you have spark issues. Did you check the plugs to make sure they aren't cracked and shorting to the block or somewhere else? Take the plugs out and shoot a little blast of gas into the cylinders directly to see if it fires that way. If it doesn't, then you still have a spark issue into the cylinders to ignite the fuel.

 

[Mazey6]

Re: 20 HP Mercury with Fuel issue, Please Help

success... there was a couple of issues;
1. even though there was a spark, it just wasn't strong enough. took magneto off and cleaned wire connections. it was full of crap so now all cleaned out and big blue spark, what a difference.
2. replaced the cracked fuel pump but still took a while to get this 'primed'. what was happening was when you used the bulb to prime the carb that was fine but the fuel would fall back down the tube towards the bulb and it would then take a lot of pulls to get the fuel back up to the fuel pump. so the secret was to keep the pressure on the bulb. i'm going to change out the bulb as it was never getting rock hard. this was easily spotted by taking the fuel pipe off the carb and pull starting the engine as the fuel should be coming out the end of the pipe. if not you have a problem between the tank and the fuel pump. with the fuel pump off we checked that air was being forced out of the cylinder ports that feed the fuel pump and they were fine so thats probably worth a look to.