Northwest Fishing Reports

I own a 5hp outboard already but my friend gave me his mercury 40 4hp gnat that has been unused in couple years. he gave it to me for free and would be good if I can get it to start up and work. His son was the last ones who had used it prior to being garaged so I don't know much of its history.

i noticed upon opening the cover that the gas tank had dark liquid with debris in it. also in the fuel line leading to the filter was ffull of debris. Awkward. Please second my decision to clean out the filter and fuel lines.

I added 2 new spark plugs. gave it a pull and it didn't start up.
i checked the plugs to see if i got any spark and there was spark. But i didn't smell fuel on them. So maybe i assume fuel is not flowing through?

Im thinking i should open up the carb, clean it. and clean the fuel lines/filter. But any suggestion would be much appreciated.

Definitely open up the carb and clean it out. Since it sounds like you tried starting it with the potential gunk in it, you should probably pull the carb off completely and clean out all the jets and needle valve. More effort, but worth it in the long run.

Cleaning out the carb, fuel lines, fuel filer and gas tank are wise decisions and tend to fix the majority of starting and running issues with outboards.
How old is the motor? One thing that can get overlooked is the emergency kill switch key. If one isn't fitted, the motor won't spark/start.

If they used ethanol fuel in it Id replace ALL the fuel lines and filter rather than clean them. Also any gaskets should be replaced - especially any rubber gaskets.

Ethanol in the fuel dissolves the older fuel lines and rubber gaskets and leaves crap in the fuel which will plug up the carb and fuel filters again if you dont replace all that stuff with new ethanol resistant materials.

The fuel lines and rubber gaskets on older motors were not ethanol tolerant. Some older fuel filters had plastic parts that also softened or dissolved.

Also clean the tank very very well and if there is a fuel hand pump/primer - and its hoses - that will need replacing as well.

Id also recommend you only run non-ethanol fuel in it from now on.

Oh - spark plugs are cheap - put a new one in

So I started with adding new spark plugs (they fired when i tested them), cleaning the fuel tank and changed the fuel lines with new ones. I opened the valve to see if the fuel would reach the end point where it connects with the 90 degree fitting and surely the fuel came running. Check.
Unscrewed the 90 degree fitting and found the strainer, had little to no debris in it. Check.
Unbolted the carb, cleaned it, and opened up the float bowl. Now it's strange cause I thought there would be fuel gushing out as soon as I opened it but in this case there was none...

Right then I knew the problem was between the float bowl and the 90 degree fitting.
Turns out there is a spring that is wrapped around the end of a plug that had corroded away. This caused no fuel to pass the 90 degree fitting. Lastly, I cleaned up the float bowl and so.

So now I'm here...seeing if I can replace this spring. Any ideas?
Sorry about the quality

Good job on getting in and finding the problem. I'm having a hard time visualizing this 90 degree fitting/spring/plug description. Where exactly in relation to the carb does this spring come into play? It's not for the needle valve is it?

BentRod wrote:Good job on getting in and finding the problem. I'm having a hard time visualizing this 90 degree fitting/spring/plug description. Where exactly in relation to the carb does this spring come into play? It's not for the needle valve is it?

I just found out the "plug" thing is the nozzle.
I'll try to explain it to the best of my ability about the fitting/nozzle/spring mechanism. So here goes. Use 2 diagrams I provided to try to help out my flaws.

The nozzle is a "plug" that controls the flow in and stopping of fuel into the float bowl. The nozzle's bottom end is wrapped by a spring which is pushed (to close flow in of fuel) and pulled (to draw in fuel) by a O Ring that floats like a tube in the float bowl.
When the fuel rises/reaches a certain height/volume in the float bowl, this causes the O ring to rise up causing the spring to push up on the nozzle to close the fuel entering from the fitting.
When the fuel drops to a certain height/volume in the float bowl, this causes the O ring to drop causing the spring to pull on to the nozzle which in turn opens a passage for fuel to enter in from the fitting.

If you get a rebuild kit for the carb it will have that spring, a new needle/float valve and seat, new float, maybe some new jets and new gaskets and other basic parts you need. It will be well worth the small cost. Id also get some carb cleaner from the local auto parts store and soak the carb body for a day or two. Then use an air compressor to blow out the small internal passages.

Looking at the pics of that carb again, it looks pretty nasty. If dipping it in carb cleaner and working on it with a brush doesnt work, you may need to take it in to a shop to be cleaned. They use ultrasonic cleaning. That can get $$ though.

Larry3215 wrote:Looking at the pics of that carb again, it looks pretty nasty. If dipping it in carb cleaner and working on it with a brush doesnt work, you may need to take it in to a shop to be cleaned. They use ultrasonic cleaning. That can get $$ though.

Larry3215 wrote:If you get a rebuild kit for the carb it will have that spring, a new needle/float valve and seat, new float, maybe some new jets and new gaskets and other basic parts you need. It will be well worth the small cost. Id also get some carb cleaner from the local auto parts store and soak the carb body for a day or two. Then use an air compressor to blow out the small internal passages.

It's cleaner than what you see now, I took pictures before cleaning.
I'm looking thru the web and can't find anyone who still sells that particular repair kit. Must be too old so they discontinued it.

There is this though, on another aftermarket repair kit, that contains somewhat of the same stuff I need.

I'm wondering if it would fit and still work properly...

check at a boat shop that services outboards, they are usually very helpful, and will get you what you need with less Guessing and hoping what you order off of the internet is correct. you may have to wait a week for the shop to get it in from their supplier, but it should be the right parts. I agree with all above, that since this sat for some time, the carburetor needs a good cleaning, since the son that last used it did not run the gas out of the carb, and the jets and stuff are probably all gummed up

You would have to be very very lucky for a part from some random carb to fit. That would be like trying to get a Ford part to fit a on a Mercedes. Not likely to work

Call around to local Mercury dealers and see what they say. You may be able to get a newer carb that will work on that motor, but you will need to find a Merc mechanic who really knows his stuff.

ncwflounderer wrote:check at a boat shop that services outboards, they are usually very helpful, and will get you what you need with less Guessing and hoping what you order off of the internet is correct. you may have to wait a week for the shop to get it in from their supplier, but it should be the right parts. I agree with all above, that since this sat for some time, the carburetor needs a good cleaning, since the son that last used it did not run the gas out of the carb, and the jets and stuff are probably all gummed up

Larry3215 wrote:You would have to be very very lucky for a part from some random carb to fit. That would be like trying to get a Ford part to fit a on a Mercedes. Not likely to work

Call around to local Mercury dealers and see what they say. You may be able to get a newer carb that will work on that motor, but you will need to find a Merc mechanic who really knows his stuff.

So I called about every repair shop or mercury dealer and they all had the same answer. They don't carry any parts for this motor anymore and they can't order them because they have been discontinued.

http://www.ebay.com/itm/Carburetor-Tecu ... 2a4349918f" onclick="window.open(this.href);return false;

This 4hp aftermarket carburetor looks very very very similar to the one on the motor.
The exceptions are the shafts for the choke+valve and the fitting for the fuel line.

If possible, where I can exchange the shafts and unscrew+exhange their fitting with my 90 degree fitting, would it still work?

look for an Evinrude, mine is from early 80's and never had problems getting parts

EBay has tons of old motor parts. There's a few EBay stores that do nothing but surplus and old boat and motor parts. I'd be really surprised if you can't get about every part for that motor online.

ncwflounderer wrote:look for an Evinrude, mine is from early 80's and never had problems getting parts

Bodofish wrote:EBay has tons of old motor parts. There's a few EBay stores that do nothing but surplus and old boat and motor parts. I'd be really surprised if you can't get about every part for that motor online.

Couldn't find any at the moment, but I'll look time to time.

Yes! My friend gave me the other spare carburetor he initially had for the motor.
But bummer, no needle...and the one i have now, its needle is broken off also. Probably from kids poking into the choke entrance with a flathead.
Anyone got any ideas which alternative need would fit and operate same as the old?

Are you sure the needle is broken? Not sure if they can hit that with a screwdriver? Anyway check here http://www.marineengine.com/parts/mercu ... s/40-1-cyl Does not look the same but maybe they will have the parts you need. Good luck I hope you can get it running again. Sometime you can talk with the shop they will always have extra parts and put together what you need.

FYI is this it? http://www.ebay.com/itm/Mercury-4hp-out ... 83&vxp=mtr