9.9 Johnson mystery

[Ksmith0110]

I got this 9.9 (1977) and it had low compression on 1 cylinder. Put a new head on it and it seems fine. 110 top 105 lower. I started it up and let it run for about an hour in a barrel, in gear. I checked the tep at the head and it showed 141F. Everything seemed fine. I shut it off and left for a couple of hours. I came back and tried to start it and it will only run if you play with the choke. To keep it running I have to hold the choke on and once the rpm starts to drop, open it up. If I keep doing this it will continue to run. If I leave the choke on or off, the motor dies. I've had the carb off several times and found nothing wrong. (that I can tell anyway) I've also checked the motor when cold vs. warm, thinking it may be an ignition problem but doesn't seem to make a difference. Any Ideas?

 

[bktheking]

Re: 9.9 Johnson mystery

Have you rechecked the compression since you ran it?

 

[Joe Reeves]

Re: 9.9 Johnson mystery

Carburetor out of adjustment..... Fuel pump failure?

Fuel Pump Check: Remove the fuel hose from the engine temporarily and pump it up hard. If it pumps up hard, and while holding hand pressure on it, it doesn't lose that pressure, the bulb valves are okay..... go to the next test.

Connect the fuel line back to the engine. Pump the fuel primer bulb up hard. After it's hard, keep a slight bit of pressure on it. If the bulb slowly compresses, and fuel isn't flowing out of the carburetor (flooding), suspect a cracked fuel pump diaphragm.

(Fuel Pump Diaphragm Test)
(Two Hose Type Only)
(J. Reeves)

Note: This pertains only to the regular Two Hose type fuel pumps.

Leave the hoses attached to the fuel pump. Remove only the two screws that attach the fuel pump to the powerhead. Re-insert those two screws and install a nut to each of them so that the fuel pump is securely clamped together. With the fuel line attached to the engine, pump the primer bulb while observing the pressure/vacuum operating hole on the back side of the fuel pump. Should any fuel leak out that hole, the diaphragm is faulty.

If the diaphragm is faulty, the fuel pump will require rebuilding or replacing. Note that repair kits are not available for all fuel pumps, in which case replacing the pump would be necessary.

If no leakage exists within the fuel pump, it could still be faulty. Test this by simply having the engine running and constantly pump the fuel primer bulb (acting as a manual fuel pump). If the engine now runs normally but dosen't when you quit pumping the bulb, replace the fuel pump.

Carb Adjustment:
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[petryshyn]

Re: 9.9 Johnson mystery

Have you done this when cleaning the carb? Be sure the passages are clear.

 

[Ksmith0110]

Re: 9.9 Johnson mystery

I have not checked compression again, but I did put a new head gasket on. I never messed with the aluminum plug on top. I tried the fuel pump but only screwed it up, so I put another on on and it does work. I put new plugs in. I just don't understand how it could run for an hour and then refuse to run again. The carb linkage was messed up and I had to wire the throttle open just a tad, to run it for that hour, but still, if it ran so good for so long what could've happened? I think I've checked all the obvious stuff, but I've been told to get a carb kit and go through it. Maybe I'm pig headed, but again, if it ran for that long I would figure the carb is okay.

 

[bktheking]

Re: 9.9 Johnson mystery

Not to insult you but the last 9.9 head gasket install from a gent on here asking the same question didn't torque his head down properly, bolts loosened and he couldn't start it, highly unlikely in your case but.......

 

[Ksmith0110]

Re: 9.9 Johnson mystery

I checked the head bolts for fun and they seem ok. I started messing around the other day and built an engine stand to hold some of the motors laying around. After I put the 9.9 on the stand, I decided to mess with it again. I found the fuel line had a kink in it. I straightened it out and tried starting it again. It fired up and purred like a kitten! I couldn't believe it was something so simple/stupid. Then out of nowhere it started acting up again. I bit the bullet and put a carb kit in. I removed all the aluminum plugs and cleaned everything out really good. When I put it back on, it fired right up and purred like a kitten! Then after about 5 start and stops it started acting up again!! I tried another fuel pump, checked the plugs, made sure the fuel pump is pumping, the vent on the tank is open, fresh gas & oil, the fuel line from the tank to the motor is new as of last year, and I used it all day today on the lake just to make sure. (that's a whole other story, anyone know about the lower units on 8 hp. Johnson Sailmaster motors?)
I guess I'm just frustrated It's either sucking too much air, or not getting enough fuel. I managed to keep it running if the choke was almost all the way closed.

 

[bktheking]

Re: 9.9 Johnson mystery

Did you adjust the low speed needle? Typically if the choke has any play on how it runs then the carb is still dirty or you may have a bad upper/lower seal.

 

[Ksmith0110]

Re: 9.9 Johnson mystery

What do you mean upper or lower seal? I tried messing with the needle but it didn't help. Besides, it had been runnig great just 5 min. earlier, and the needle was fine then?

 

[bktheking]

Re: 9.9 Johnson mystery

Crank seals- Getting away from the carb for a minute, acting up how? Describing an issue with a motor is very difficult, you almost have to see it run to find out how it's "acting up".

 

[Ksmith0110]

Re: 9.9 Johnson mystery

Like before, you choke it to start it, and it starts right up and runs but then the rpm starts to drop, if you flick the choke shut and open it right back up, the motor starts gaining rpm, then it slows back down, flick it and it revs back up. If you close the choke and hold it, it dies. If you leave the choke open it dies. It only runs if the choke is almost all the way closed. Then all of the sudden it runs fine - even with the choke off. Then after a few cycles of start/stop it starts acting like it needs the choke flicked to keep running.

 

[Joe Reeves]

Re: 9.9 Johnson mystery

Pump the fuel primer bulb constantly, acting as a manual fuel pump. If the engine runs normally, suspect a failing fuel pump. If it does not, suspect that something has entered the carburetor and is blocking the high speed jet.

(Fuel Pump Diaphragm Test)
(Two Hose Type Only)
(J. Reeves)

Note: This pertains only to the regular Two Hose type fuel pumps.

Leave the hoses attached to the fuel pump. Remove only the two screws that attach the fuel pump to the powerhead. Re-insert those two screws and install a nut to each of them so that the fuel pump is securely clamped together. With the fuel line attached to the engine, pump the primer bulb while observing the pressure/vacuum operating hole on the back side of the fuel pump. Should any fuel leak out that hole, the diaphragm is faulty.

If the diaphragm is faulty, the fuel pump will require rebuilding or replacing. Note that repair kits are not available for all fuel pumps, in which case replacing the pump would be necessary.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

 

[the machinist]

Re: 9.9 Johnson mystery

One thing that is cheap to replace is the neoprene O-Ring in the fuel line connectors, sometimes these get deteriorated or abated & do not make a good seal on the fuel shaft at either the tank or the motor, which would suck air.

 

[reelfishin]

Re: 9.9 Johnson mystery

I've got one here doing the exact same thing.
It was an eBay win for really cheap, it needed a set of upper motor mounts but otherwise looks like a new motor. Mine is a 1986. Its got 141/142 psi on both cylinders.
It starts up and runs fine, idles, makes good power, and will run all day but after the first shut down and restart it'll act up and won't run without the choke. If you let it cool down overnight, it again will run fine, just don't shut it off. I've run it the length of the river here, almost 3 gallons of fuel through it without shutting it off and it's fine. But if I run it for 10 minutes, and shut it off, it won't restart without the choke, it starts hard and won't run with the choke off, and runs poorly at that.

I've swapped in a known good carb, known good power pack, stator, flywheel, fuel pump, fuel hose, tank, etc. with no change. At this point I'm convinced that whatever ails it is in the power head assembly, either a seal issue or maybe an exhaust issue.
A local dealer had said to try running it without the cover on it, but that don't make much sense since the first time it did it to me, the first thing I did was pull the cover and mess with the carb. On mine, it don't matter how long it runs, it will run fine till its shut down and restarted. The amount of time it sits not running does seem to make it worse, a longer hot soak makes it very hard to restart and it needs more choke once it starts. With mine, it will only rev about half way or so when it acts up but that's with the choke on. When its running right, it's 100% even if you run all day long, just so you don't shut it off and expect to restart it. It's not my main motor, just a spare I picked up, so I've not really spent a lot of time dealing with it but seeing this post reminded me that it's sitting there in the corner.

 

[Ksmith0110]

Re: 9.9 Johnson mystery

It doesn't seem to matter if it sits for a while or not. Once it starts acting like that it's done. I don't know what happens to make it magically start working again. When I first got it running it ran in a 55 gal. drum for more than an hour, in gear at just above idle. I started it and stopped it several times, it worked fine. I shut it off to go to my kids soccer game and when we got back I tried to show the wife how good it ran and it made me look like a fool.
I did however notice (and I just thought about it today) there is a number on the main jet, 54. I looked in a motor manual and saw the number for a 15 hp. is 54 and the number for the 9.9 is 38. So even when it is running, it's running rich (I guess).

 

[Joe Reeves]

Re: 9.9 Johnson mystery

Jet size .038 = 9.9hp..... Jet size .054 = 15hp. The engine is not running rich.

Someone has changed the carburetor from a 9.9hp model to a 15hp model carburetor effectively increasing the hp of your engine.

 

[Ksmith0110]

Re: 9.9 Johnson mystery

A marine mechanic told me the carb bore is bigger, intake is different and the exhaust housing on a 15 is different. So changing the jet will give it more fuel but without the extra air it just runs richer.

That said, I recieved a carb that I ordered off ebay, threw it on and hooked up the fuel line and bang...works fine. I stopped it over and over, and it always started back up and ran fine. I guess something is actually wrong with the carb that was on it.

 

[Joe Reeves]

Re: 9.9 Johnson mystery

The later 9.9/15hp models had different heads, tuning tubes, exhaust areas etc that differed..... the earlier 9.9/15hp models did not and everything was identical except the carburetors. Many a 9.9hp was upgraded simply by installing the 15hp carburetor.

The previous carburetor simply needed cleaning and rebuilding.... something within it was being overlooked. No matter but someday double check that carburetor thoroughly..... you may want to try the difference in power.

 

[reelfishin]

Re: 9.9 Johnson mystery

When you say later models, what years are you considering later?
I've always grouped those motors in three groups, 1974 to 1983, 1984 to 1992, and 1993 and newer. That thinking is mostly due to the net hp rating change in 1984 and the upgrades that came about after about 1993 or so.
I was always told to stay away from the older models simply because of the hp ratings, supposedly the post '84 motors were a lot more powerful than the older ones?
I was always under the impression that the carb and exhaust tube had to change to make the jump to a 15hp but the oldest of these that I've dealt with has been about a 1981 or so model. I see that the 1980 and back models both use the same inner exhaust housing and gasket.

 

[bktheking]

Re: 9.9 Johnson mystery

Well there's a guy a few posts back looking for a 15 carb, i'm sure he'll gladly buy it off of you, PM him for fun.

http://forums.iboats.com/showthread.php?t=442185

Probably a one off poster till his motor messes up