1992 Johnson 9.9 Won't Run Right

Hello all--kinda long post, but I'm stumped. I picked up a Johnson J10RENA of off Craigslist for $200. It had been sitting for several years, but looked good.

So far, here's what I've done with the motor:

-Carb cleaning & rebuild with oem kit. The carb was filthy, but I've managed to get it cleaned up and now have all the right gaskets in all the right spots. (took me a few tries to get it right) All orifices and jets are open and clean.
-New water pump impeller
-Changed lower unit lube (old stuff was dark, but no water)
-New thermostat kit (a little bit of mineral buildup in the housing, but not bad)
-New head gasket (after seeing the mineral buildup in the 'stat, I wanted to see what the cooling jackets were like. They were clean and the cylinders/pistons were just fine. A little carbon on the piston crowns that I cleaned)
-Rebuilt starter rewind spring assembly (what a pain) and new starter rope.
-Dismantled, cleaned up, and repaired twist throttle and cable assembly.
-Very strong, even compression
-Good spark (pull the plugs, ground them, pull the rope, I get bright blue sparks with sharp "snaps" when each one fires)

OK . . . here's the rub . . . At best, I can get this thing to fire at 1/2 throttle or more, it may run for ~15 to 20 seconds, slobber down, and die. Lots of heavy smoke. When it's running (?), it's VERY rich and unresponsive. At first, I suspected that the plastic housing that holds the main jet wasn't sealing on it's top & bottom, so I verified that the gaskets are being compressed properly. (items 2, 6, 8 on exploded diagram found here http://shop2.evinrude.com/ext/index.aspx?s1=37ab03687d3a363c094c11b33e628b2e)

At this point, I'm stumped. I will tear into the carb (again) and see if I've missed something. Does anyone have any thoughts? (reed valves, ignition, ???) Everything I've ever known says this motor should run like a scalded ape.

Sorry for the long post.

Terry

Re: 1992 Johnson 9.9 Won't Run Right

From your description, especially the rich mixture comment, I'm betting you still have a problem with the carburetor. I know you've taken it apart and cleaned it and put a new kit in it. Did you unscrew the main jet orifice and clean and inspect it? It takes a special screwdriver to get it out.

Also, did you replace the needle and seat and set the float properly?

One final possibility, and I'd check this first. If the fuel pump has a hole in the diaphagm, it will cause an extremely rich mixture by dumping fuel into the crankcase. It's worth checking.

Fuel pump repair kit is part no. 0393088. For $15, you get what is basically a new fuel pump.

Re: 1992 Johnson 9.9 Won't Run Right

http://forums.iboats.com/showthread.php?t=244013 what are the compression #S?

Re: 1992 Johnson 9.9 Won't Run Right

Terry here logged in from work (old login with different ?handle?)

The float level is properly adjusted and the float valve works as expected. I?ve removed and cleaned the main fuel jet (on the side of the plastic nozzle well). I only needed a regular screwdriver to remove the jet from the nozzle well. This is a 1992 model with the black plastic float bowl and black plastic top cover. There is a small rubber tube from the nozzle well to the top half of the carburetor for the low-speed circuit. All of these passages are clean. If the nozzle well isn?t sealed (top & bottom), it could also allow extra fuel into the venturi and cause these symptoms?that?s where most of my efforts have been focused so far. I?m 90% sure that the carburetor is OK, but I?ll take one more look at it.

Your thought about the fuel pump is a good one! If one of the diaphragms is leaking into the crankcase, it could easily cause these symptoms. Also, when pumping up the fuel line bulb, that could easily ?load up? the crankcase with raw fuel. I will pull the pump as an assembly, pump with the bulb, and see if fuel is getting into the crankcase port.

I already have the fuel pump rebuild kit, but was hesitant to dig into the pump. By reading some of the online info about rebuilding that animal, I wanted to try to get the engine running first. I did pull off the fuel line to the carb for a couple of seconds while the engine was running?there was flow, but it wasn?t real strong. I will tear it down and see what I?ve got. Based on the overall condition of the engine, I can almost guarantee that it?s the original 1992 pump.

I don?t believe my compression gauge?s accuracy--it reads ~85lbs on my Chevy Tahoe with only 20,000 miles! (el-cheapo model from China!) That being said, the same gauge reads ~53lbs for both cylinders on the Johnson, so I believe I have good compression and I know I have good balance. It feels plenty strong (solid thunk-thunk-thunk when pulling the starter rope or manually turning the flywheel). When I had the head off, there were absolutely no signs of any problems on the cylinder walls. I did not pull the intake or exhaust covers to inspect the rings?I don?t have enough evidence to suggest that I have a sticking ring problem.

What spark plugs/gaps are recommended for this motor? I like to troll a lot, so it will be idling for extended periods. On other trips, I may take it duck hunting, so it may be at WOT for extended periods. If needed, changing the plugs for these different situations doesn?t bother me. Suggestions?

Stay tuned.

Re: 1992 Johnson 9.9 Won't Run Right

It does sound like your compression gauge is reading really low, based on the numbers from your vehicle. I don't have that engine, and don't know the recommended plug for it, I'm afraid.

Re: 1992 Johnson 9.9 Won't Run Right

Recommended plug for typical use is Champion QL77JC4 @ .040.

Re: 1992 Johnson 9.9 Won't Run Right

I bought a gauge that read like that - replaced the valve and it worked fine.