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CarbonSink62 08-13-2012 12:40 PM

1981 Evinrude 9.9hp 2str starts but won't run
Disclaimer: This engine came with Zen Again and I already wish I'd just left it there instead of 'investing' time and money in it, but here we are.

I rebuilt the carb (Yay, me!) and it starts on full choke, but dies before I can pat myself on the back (Boo, reality!). The only way I've found to get to run again is to wait about 2 hours and then I get another 8-10 seconds of operation.

Once it starts, if I get onto the choke right away, I can go to half choke and prolong the run to maybe 20-30 seconds. Then it dies.

I have replaced the water pump, plugs and wires.
I have 2 thoughts:

1. Fuel pump - I'm guessing that the pressure I put with the bulb sees the engine through start up, but the run can't continue without more fuel and the pump isn't working. I've tried to keep pumping the bulb while runs, but it did not help.

2. Rich/lean mix - This engine has a needle valve that is labelled rich/lean; the rebuild instructions said to seat it gently and then back it out one full turn. The starting instructions say to set the dial to the middle. The dial is on the knob; the knob is not keyed to the shaft of the needle valve. So the valve is still one turn back from seated.
Other observations:

The START position on the throttle is one step below FAST, but initial operation is very quiet. It purrs, it doesn't roar. In my experience with other engines starting on full choke, the engine screams until you get to half choke and drop the throttle a little. That leads me to suspect the rich/lean setting.

The throttle itself is very puzzling, the twist grip moves a couple of linkages one of which eventually pushes a cam follower on the carb and opens the butterfly valve to allow more fuel/air mixture into the intake manifold. This follower is only activated when the throttle is all the way to FAST; on START and below (SHIFT and SLOW are the other labels) the cam follower is untouched. So some other mechanism must be controlling engine speed below FAST, but I can't see what it is. I haven't ruled out the possibility that I reassembled the cam follower linkage wrong, but I can't see how.

dabnis 08-13-2012 01:16 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
When rebuilding the carb you may have missed some very small debris in the air/fuel passages. On the many outboards and motorcycles, both 2 & 4 stroke that I have had, about the leanest low speed needle adjustment was 1-1/2 turns out. Suggest you try it there for starters, maybe going richer until it starts to stumble a little then back in just until it smooths out a little. If it is not a mixture problem there is likely an obstruction from the tank forward. I had the same motor but can't remember the linkage set up. A good shop manual should show the proper set up. Maybe the float is stuck shut or not adjusted properly? I had a carb on a Honda 2HP that got plugged up. I cleaned out but it never ran perfectly until I gave up and put a new carb on it. Let us know what you find.

All of this assumes you are getting a nice fat bright blue or white spark when grounding the plug out of the motor?and pulling it over.

Paul T

Sea Dawg 08-13-2012 01:34 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
The fuel pump fills the carb bowl, but vacuum thru piston operation draws it into the reeds. Thus I'm thinking if it's the fuel pump would take more than a few seconds to empty the carb bowl . It should continue running if you pump the hose bulb even if fuel pump is bad. Since it's running initially continue to focus on the fuel system. The hose is often suspect as there are orings that leak, check valves that stick, or crack in the hose or bulb. The fuel delivery to the carb is suspect, if when the engine falters a quick shot of starting fluid will carry it a few more seconds.

Take the spark plug out right after it shuts down and see is it dry? On mine, that revealed tiny water drops on the piston which were from leaking by the head gasket. No other symptom other than I could start it but wouldn't keep it running. It also occurred right after replacing water pump so maybe the higher pressure brought on the water leak. This isn't perfect troubleshooting but maybe will keep you going today.

The engine speed below the point of cam roller moving the butterfly is controlled by rotation of the magneto plate which advances the spark timing.

dabnis 08-13-2012 02:26 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run

Forgot to ask, did the motor ever run properly? If so,was there any work done on it afterwards? Assuming you have good spark and it is timed properly you might try another tank, and fuel line from tank to motor. You could also try gravity feed directly to the carb through a separate line. If none of that works it may very well be the carb which could be re-cleaned and blown out with compressed air. Or you could just gamble on a new one? As mentioned above if the plug is dry after the initially firing it is likely starving for fuel. My guess is that if the motor sat for a long time without having the carb drained the carb was/is pluggrd up?

Pasul T

bubb2 08-13-2012 03:08 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
fuel filter; it's a screen type filter lower than the carb on the right front of the engine. black box with a screw in the middle. Clean it.

CarbonSink62 08-13-2012 03:16 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
Thanks, guys.

I've been jumping around (doing things out of order) and did not clear out the fuel line before installing the rebuilt carb, so I might have sent crap into the newly cleaned carb. I'll be tearing it apart again to check if I can't get it running soon.

I replaced the wires and plugs 'just because'; the next time I start it, I'll pull the plugs and look at them immediately post mortem. I'll check for spark then, too. I've read that it should jump a 3/8" gap. I gapped the plugs when I installed them.

A shot of ether after it dies does not bring it back, only time will fix it. That says 'flooded engine' to me, but I write software and have very delicate hands. ;)

I bought a new tank and fuel line so all that should be 'ok'.

BTW - I have never seen this engine run, the dealer said it was 'tank tested' by them; I'm ready to call BS on that.

CarbonSink62 08-13-2012 03:18 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run

Originally Posted by bubb2 (Post 908989)
fuel filter; it's a screen type filter lower than the carb on the right front of the engine. black box with a screw in the middle. Clean it.

Did that, thanks. There was some crap in one corner, but it was clean enough (not fouled) to supply fuel.


tommays 08-13-2012 03:25 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
1981 is OLD for a fuel pump and all the dirt in the fuel has to pass through the TINY check valves in the fuel pump

The KIT does not cost much BUT is a bit of a PITA compared to droping in a new ORGINAL fuel pump as you have to beware of knockoff spare parts

travlin-easy 08-13-2012 04:19 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
I'm guessing with this one, but almost positive that you failed to set the carburetor float properly. The setting is critical, and in some of the old rebuild kits they supplied a float gauge. You only have to off a fraction of an inch and the engine will either flood, or starve for fuel.

Good Luck,

Gary :cool:

CarbonSink62 08-13-2012 04:34 PM

Re: 1981 Evinrude 9.9hp 2str starts but won't run
The kit didn't have a gauge, but the procedure did show one.

I 'eyeballed it' for side-to-side and measured the drop with a ruler. I could have screwed it up.

If I order a new fuel pump, I'll put a gauge in the cart as well.

I'm buying a new 4 stroke before the end of the season, I need to get this one running so I can sell it; it would be nice if I could use it to cruise the river. I don't think I'll ever trust it enough to go play down by the the drawbridge.

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