9.9... Got spark, got compression, got fuel, can't even make it fart!!!

[JustJason]

Ughhh... Another toon from hell!!!

Early 90's vintage. Lost foam cast block (integral head)
Compression 80 and 80
Spark, hot and blue, jumps 1/2in on the board no problem.
Fuel, Carb and pump rebuilt by yours truely... flow tested it with a blowgun. Was dirty before but not the worst i've ever seen.

This thing doesn't do anything. Wont start, stutter, sputter or fart. Not even by shooting fuel down the throat of the carb.

Timing, Hooked light up to plug wire and hooked plug wire up to the board. In neutral Timing is steady at 8btdc, when the throttles wide open, timing is 36, as per specs. So I can't imagine its the spark timing or something with the triggers/flywheel. Verified 0 on the flywheel is #1 tdc. Even checked for a bent crank and the pistons are exactly 180 apart.
I know I'm firing via using a spark board, a timing light, and my KV meter. I'm getting 5KV at cranking rpms.


I check the reeds by just placing my hand over the carb. There is no blowback. But I don't really feel my hand getting sucked in either??? Placed a light plastic baggie over the carbs throat and cranked it and even that didn't get sucked in. Pulled the carb again and sprayed J/rude 6-1 foaming oil at the reeds while cranking and it does get sucked in a little, but not a whole lot. I don't know if that is normal for a 9.9 or not??? Checked the bleed system just for the hell of it, thats working the way it's supposed to.

So like... what the H??? Anybody know if these 9.9s can pull an air charge from anyplace else other than through the carb? No block/gasket leaks that I can find with foaming oil.

Going back to it in a bit and am going to lock each piston at tdc and do a leakdown test. I'm going nucking futs... anyone have any insight?

 

[CharlieB]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Jason,

What happens when the inner crank seal begins to fail, the cyl cases begin swapping air instead of drawing in thru the intake.

Block the motor with a cyl at BDC, and leak down test the INTAKE side of a cyl, listen for the air leaking out the other intake to confirm a faulty inner seal ring.

 

[gabriel charest]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

hehe .. do you check if this engine was rebuild and somebody put the piston on the wrong side??????? it happens to me on one outboard......i found that just before i was ready to use a big big hammer ....

 

[JustJason]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Charlie,
Thanks for your insight. But I don't believe its the center labrynth seal. I don't even see one in the parts blowup for one.

Heres the short story. Customer has 2 toons. 1 with a 40 Mariner(boat #1), other with the 9.9 Merc(boat #2). Customer goes and buys gas, fills up a gas can and dumps some into boat #1. Gets out on the lake, 10 minutes later boat #1 starts running like junk so he brings it back in and gets boat #2.
Boat 2 starts running like junk after a few minutes. Customer takes boat 2 back to dock and runs in neutral at 1/2 throttle (or so he says) for a few minutes then the motor dies. I asked him "how exactly" it dies. Did it cut out and spin for a second or 2, or did it just lock up. Customer says it locked up.

So the thought here is bad gas/water in gas. I look at the supply can. Take a sample, has water but not too much. Gas can has a lot of debris in it however. Dirt, leaves, weeds, you name it.

Tested boat 1 has a clogged fuel water sep, had non marine fuel line zip ties on the entire fuel system.
Changed water sep, changed on motor inline fuel filter. Changed all zip ties to the correct ones. Drained fuel tank. Cleaned out some crap from the tank vent. Tested the boat side fuel system again after the sep filter change. Everything checks okay so I go to float it and I ran it wide open for 15 to 20 minutes with no problems.... hopefully problem solved.

Tested boat 2, everything I checked checks out. Compression nominal. Spark at the correct time. Even sprayed fuel down the throat of the carb and I can't even get a pop. Pulled the car (again) and started hosing 6-1 at the reeds while cranking with the plugs out and it took a good 20 seconds of crank time before I got some of the oil out of the plug holes.
The other thing I don't get about this 9.9 is this. It wouldn't matter if it had a bad center seal because when I pulled the reeds out you can see that both cylinders share a common lower crankcase area. There is nothing that seperates the 2 areas/lower crankcases. If 1 piston comes down, its going to vent into the other sides lower crankcase. Doesn't make too much sense to me at the moment. Looking at the lower crankcase with the reeds removed I do not see anything that is physically broken. Honestly the way its acting is like the 2 cylinders have a hole someplace inbetween them, but unless I opt to pull this whole thing apart I'm still just taking my best possible guess. I can't get any "suction" through the carb or build up. Oh well... i'm ready to kick this thing into the pond.

 

[Robj]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Just a WAG but isn't 80 psi on the low side? I would like to see at least 100 psi. Just a suggestion, you know more about these things than I do.

Good luck and have a great day

Rob.

 

[scipper77]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

I'm making this test up but...
What would happen if you brought one piston to TDC and blew say around 80psi compressed air into the plug hole (with both plugs removed)? I guess what has me a little confused is that you say you have compression. If you were swapping air between both cylinders wouldn't that show up on a compression test??

 

[JustJason]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

I'm making this test up but...
What would happen if you brought one piston to TDC and blew say around 80psi compressed air into the plug hole (with both plugs removed)?

Your not really making anythig up. Thats a typical leakdown test. It was done and rings hold up fine, leakdown is less than 20%. I even slowly lowered the piston down (via breaker bar on the flywheel) and made a mark on the flywheel when the ports open. It was the same on both cylinders.

I'm just going to have to pull the powerhead and split it. Everything else is making sense except for a very very weak crankcase pulse. I can't get any suction through the carb. I'm sure once I open it up I'll see the culprit.

Damm lost foam blocks.... why can't I just pull a head instead of pulling MY hair out!!!

 

[emckelvy]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Just a silly question, is this one of the designs where the bottom of the crank is actually sealed by the driveshaft O-ring? If so, and the O-ring has deteriorated, you'd lose crankcase compression via the hollow crank.

Easy enough to check by pulling the lower unit and verifying the O-ring is good.

One last thought, if you're dumping too much fuel in the crankcase she's not gonna fire either. A problem with fuel pump reassembly or leaking primer valve in the carb would do this. Just something else to check before you break out the incendiary devices!

HTH & G'luck........ed

 

[CharlieB]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

The ONLY 9.9's I know of with a shared crankcase chamber are 4-stoke motors.

2-stokes MUST have a separate crankcase chamber for the pressure/vacuum pulses to make the system function.

UNLESS, it's built like the old Detroit diesel 2-stokes, with a supercharger providing the intake pulse.

I suspect that when you open those cases you are going to find the broken pieces of the wall that USED to be between the chambers.

 

[JB]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

I am no Merc-spert and I never stayed in a Holiday Inn Express, but:

Are the bypasses sealed by seperate covers or cast in?

My instincts, developed from about 60 years of messing with small outboards, tell me that what you have is a failure in scavenging.

I would carefully inspect the intake system to be sure that the crankcases aren't swapping spit via the manifold or the reed block, and that the bypass passages are not sucking air from somewhere.

I will be very interested in learning what you finally do to fix that thing.

 

[JustJason]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

I'll follow up on this one in a few days. The customer had actually purchased another 9.9 on the cheap before I even got out to the boat "just in case".

I ended up installing the other 9.9 instead of putting to many hours into the old one. After I did the swap and lake tested everything he asked me if I knew anybody who may want the old one for parts... I gave him 50 bucks for it. I'll tear it apart over the next couple days and see what's up with this one.

JB, What do you mean by "bypass passages"? Are you talking about the bleed system? I've just never heard the term before.

 

[dkonrai]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

i have a 93, 15hp that has the exact same problem. i cant get it fired. the motor was hardly used, i checked the internals and it is in mint condition. i have 90 pounds of compression in both cylinders.
i am going nuts as well...... have you found the problem? spoke to a marine mechanic and he is telling me that the motor is low on the compression side.
the reed valves are clear and the spec'd gap is fine.

 

[JB]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

"Bypass" passages are the means by which fuel/air mix gets from the crankcase to the intake ports, JJ. Many outboards have these covered with a plate and gasket that can leak, screwing up the piston's pumping action. That pumping action is what I am calling scavenging. . .drawing fuel air in through the carb, then pushing it up into the cylinder through the bypass and intake ports.

 

[JustJason]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Ahhh.... Gotcha JB. I've just called "bypass passages" just the lower crankcase itself. I believe its also called the primary combustion chamber... where as the tip of the piston would be the secondary combustion chamber.

Well we will never know the end result of this one. I went to pick up the motor and now the guy decides that he wants to keep it just for the old parts on it in case he ever needs it. Starter/ignition etc. Oh well. Thanks for the insight anyways guys!!

JB, I always believed scavenging to be the act of using timed exhaust pressures/pulses to help "pull" exhaust gasses out. You don't really see it on outboards because the exhaust dumps straight down. But you would see it on tuned headers in an automotive application. Or most commonly on a dirtbike or street bike. Ever wondered why a dirtbike has a big flare in the exhaust pipe up front? Its to time those exhaust pulses. Same thing on street bikes. Some manufactors go as far as adding a valve in their exhaust systems that open and close depending on rpm to tweak the powerband through exhaust scavenging.

 

[JB]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

Anytime you use pneumatic or acoustic principles to move gasses it is proper to call it scavenging. The purging of the cylinder of exhaust gasses by incoming charge is also called scavenging. . . cross scavenging or loop scavenging.

 

[macccj5]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

just a thought-- did you try priming it through the plug hole just to make sure it would kick over?

 

[JustJason]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

I did and still no fire Macccj5.

If any of the mods feel like it they can lock down this thread as the motor is old news and I won't be seeing it any more.

Thanks for all your input guys.

 

[dkonrai]

Re: 9.9... Got spark, got compression, got fuel, can't even make it fart!!!

just a thought,
i have the same problem. i am told that if you wash out the motor with clean pure gas, let it sit, and drain down. allow the motor to dry out for a day or two. then give it a try. i guess sometimes there is crap in the cylinders and you need to clear it out. i am trying this to see if i can get my engine running. its worth a shot