Early 80's 9.9 2 stroke Merc

[Bogwoppit]

Hi All

I'm new to the forum and must say it looks good here!

I'm based in Ireland and I'm doing a service on my old Merc.

I have a new set of gaskets and diaphragms for the carb but I can't find any info on what the float height should be.

Can anybody here help me?

The part number on the carb is WMC 17, the motor serial number is 9476313.

Thanks

Allan

 

[quicktach]

Re: Early 80's 9.9 2 stroke Merc

It's a WALBRO carb. Check out their website for a tune up/rebuild guide. An OEM or Seldoc manual will help.

 

[Texasmark]

Re: Early 80's 9.9 2 stroke Merc

If that doesn't work, invert the carb with the bowl off. Tweak the tab for the float to be parallel to the top casting where the bottom half mates while resting on the needle valve....like it would be in normal operation if the fuel was pushing up on it. Disregard the bottom half of the float in your measurement as it's of variable shapes and all. Works on a lot of carbs if that's all you have for instructions.

Mark

 

[Bogwoppit]

Re: Early 80's 9.9 2 stroke Merc

Thanks guys, that's a great help.
I'm also wondering what position I should have the tuning screw when starting it back up for the first time.

I did a search on the walbro website but can't find any mention of that carb model on there.

Allan

 

[Mi duckdown]

Re: Early 80's 9.9 2 stroke Merc

Idle screw is 1 1/4 to 1 1/2 turns out, from lightly seated.

 

[Bogwoppit]

Re: Early 80's 9.9 2 stroke Merc

The gasket and diaphragm kit arrived today so I'll get the carb out and get the bits in this week.

Fingers crossed it's the right repair kit, we weren't 100% sure which to order so we got the Quicksilver part no. 1395-9761

It does look right but I suppose I'll find out soon enough. The kit was fairly pricey, ?75 or nearly $100! I suppose I could have gotten a cheaper spurious kit but things like this aren't as easy to get hold of in Ireland.

I don't know if anyone else on here has ever taken the carb out of this model of 9.9 but it's a proper b*stard to get out.

I also need to take off the prop to check which shaft type it has as it needs a new seal.

Thanks for the tips.

Allan

 

[Bogwoppit]

Re: Early 80's 9.9 2 stroke Merc

So I got the carb back in and the whole lot put back together.

It was a bit tricky to start but I eventually got it going with some idle screw adjustment.

It runs very well on an open throttle but the problem now is that it won't idle.

It just stalls when coming out of gear and I have adjusted everything that I can see on it.

Does anyone have any ideas I could try before I bring it off to the shop?

Thanks

Allan

 

[Texasmark]

Re: Early 80's 9.9 2 stroke Merc

Looks like we are addressing a low speed problem aka 2 jets in the carb, low and high speed. How did your engine idle before you redid the carb?

Remove the low speed adjustment screw and inspect the cone...sloping part of screw. Is it perfect, or is there a ring around it about mid way up? If not perfectly smooth you will have a real problem getting satisfactory idle.

If it runs good at high speed one would expect compression to be adequate. What do your plugs look like? In attempting to get it to idle, do you have a lot of smoke out of the exhaust? Do you know for sure the float is shutting off the fuel inlet valve aka needle valve. Simple test is to drop the bowl and with slight pressure on the bottom of the float, pump the bulb till firm. Relax the pressure on the float allowing fuel to flow and gingerly push it back up. With the float in the adjustment position, the fuel should stop completely. If not I'd say you are flooding the engine at idle speed. Agree on the numbers specified for initial screw adjustment.

Would be nice if you had a tach so you could tell us what your idle rpms are. You could have your throttle limit screw set too loose allowing you to idle at too low an rpm. 700 or so should be close to where you would want to run.

Mark

 

[Bogwoppit]

Re: Early 80's 9.9 2 stroke Merc

Looks like we are addressing a low speed problem aka 2 jets in the carb, low and high speed. How did your engine idle before you redid the carb?

Remove the low speed adjustment screw and inspect the cone...sloping part of screw. Is it perfect, or is there a ring around it about mid way up? If not perfectly smooth you will have a real problem getting satisfactory idle.

If it runs good at high speed one would expect compression to be adequate. What do your plugs look like? In attempting to get it to idle, do you have a lot of smoke out of the exhaust? Do you know for sure the float is shutting off the fuel inlet valve aka needle valve. Simple test is to drop the bowl and with slight pressure on the bottom of the float, pump the bulb till firm. Relax the pressure on the float allowing fuel to flow and gingerly push it back up. With the float in the adjustment position, the fuel should stop completely. If not I'd say you are flooding the engine at idle speed. Agree on the numbers specified for initial screw adjustment.

Would be nice if you had a tach so you could tell us what your idle rpms are. You could have your throttle limit screw set too loose allowing you to idle at too low an rpm. 700 or so should be close to where you would want to run.

Mark

Thanks for the reply Mark.

I don't have a tacho but I'll check the other things you mention and see what happens.

Which screw is the throttle limit screw? If it's the one that controls the contact between the throttle linkage and the throttle on the carb then it is already set for maximum idle.

It's probably due new sparks anyway so I'll replace those too.

Thanks again.

Allan

 

[Bogwoppit]

Re: Early 80's 9.9 2 stroke Merc

Right, here we go again!

I replaced the sparks last night although the old ones looked fine, they'll do as spares.

I took out the idle screw and it looks fine, no wear.

I adjusted the throttle linkage to give it a bit more throttle when it's idling.

It seems like the float and needle are shutting off the fuel correctly.

The result;

1- With the idle screw out 1 1/4 turns the engine idles fine, but stalls when I give it throttle or put it in gear.

2- When I adjust the the screw out to about 2 1/2 turns the engine runs great but will not idle.

Any more ideas?

Thanks for the help.

Allan

 

[Scott Danforth]

Re: Early 80's 9.9 2 stroke Merc

sounds like you still have a bit of dirt somewhere in one of the carb passages.

 

[Mi duckdown]

Re: Early 80's 9.9 2 stroke Merc

Assuming there is No blockage, set idle screw to 1 1/2 turns out. remove idle screw and Run a piece of 25 lb. mono fishing line in idle passage. to test for blockage.

 

[Texasmark]

Re: Early 80's 9.9 2 stroke Merc

Agree with the other's suggestions. On your 1 1/4, symptoms were as one would expect for a normally operating engine aka fuel starvation upon attempting acceleration where the low speed jet is in control. 2+ is way to much. Had you not had some blockage or something of the sort, opening the jet 1/8 turn at a time from your 1 1/4 should have shown you improved acceleration as you did so until you got it right where the engine would take throttle but that should have been near 1 1/2 or slightly higher.

Added after thought. I had a fuel problem and disassembled the carbs and all looked great; no nothing but what was supposed to be in there. I thought I'd just give the bowls a shot of compressed air anyway and lo and behold upon doing so, i dislodged this little piece of black fuel line that was partially obstructing the high speed (in my case) jet. Put her back together and wala.....problem fixed.

Case in point is that you may not catch the blockage in a visual but you can surely stir things up with air or a probe or both.

Hang in there, you'll get her.

Mark

 

[Mi duckdown]

Re: Early 80's 9.9 2 stroke Merc

Shouldn't idle be adjusted in forward gear.