2003 Tohatsu 9.8B 2 Stroke ran good now wont start

[panamakid]

I recently bought a used Tohatsu 2003 9.8 HP 2 Stroke. I brought it home and got her running on the hose.

I hooked it up to the boat and used it 3 times and it ran pretty good (17.8 MPH with me (200lbs in a 15'4" Gheenoe).


Last night I used it in a lake and it died after 2 hours of use and would not restart so I had to paddle 1 mile to the ramp.



Today I pulled the carb apart and cleaned it well with carb cleaner and a small wire to ensure all jets were clear (the low speed jet was a bit clogged).

The Spark Plugs are totally black thick with oil/carbon gunk the texture of old axle grease, beyond fouled.

Clearly it was running rich or the gas has too much oil.

I did a cold compression test, wide open throttle with 4 pulls and both cylinders read at 130PSI.

I checked and I have spark in both plugs/wires.

I changed the plugs and gas and can not get it to start at all.

I tried a bit of carb cleaner in the carb and spark plug holes to get it to fire, no luck..


Is it possible the cylinders are so clogged up with oil/carbon it wont fire?


So I have compression, spark (visual), and gas (fresh). What else is there?

I have no idea how timing works on these motors. I guess it has CDI?

Any advise would be great.

 

[Sea Rider]

The 9.8 model uses a CD/Ignition Coil Pack. If engine was working OK, timing should definitely be spot on. Was carb correctly assembled, with no left over parts ? Are fuel pump check valves ok, diaphragms in good working order, that's not dried, cracked, severely ballooned ?

Asssume you have opened fuel tank air valve, primed hose bulb untill firm, moved grip to starting position along pulling choke out, right ? wanted to start, but finally didn't so ? Plugs must be gapped to 1.0 mm tight. Fuel/oil mixture must be max 50:1, not a drop more. Was fuel/air mixture screw set at same position as it was removed ?

Having a spark is no indication the spark is sufficiently opt to ignite the fuel/oil mixture, intensity must be checked with a IC gap tester. Is it possible to try other CD/IC unit on yours, or yours onto other 9.8 engine that works fine ? That would be a quick test...

Happy Boating

 

[panamakid]

I have been trying to start it with new gas and like 75:1 oil (if it starts i will add more).

I think the issue was a 2 cycle oil from the gas station was used. Not marine TW3 type oil.

I have the air screw 1 1/2 turns out the idle screw was not messed with.

I am leaning towards a cdi issue as i feel if it were a carb issue it would still fire up for a second on the starting fluid.

I barley get a pop.

I do not have access to donor motor to trouble shoot or borrow parts from.

Is there a way to test the CDI rather than buy a new one?

 

[panamakid]

opened the carb again, very clean.

new 93 octane fuel and a light does of proper TW3 Marine 2 stroke oil 75:1 to not foul plugs.

Tried several sets of plugs, all show a bright blue spark with a crisp crack when testing for spark.

Tried staring fluids in carb, not starts,

a light spray in the cylinders and i get the slightest POP like it wants to start.

So I have compression 130/130 , fuel, and spark ( Visual).

 

[pvanv]

Never ever use any kind of wire to try to clear any carb passage. You may have done more damage than good. Proper carb cleaning involves complete disassembly and a full 4-hour soak in real carb cleaner, followed by a good blow out with either compressed air or generic carb spray; then a careful reassembly, paying close attention to float height. There is no air bleed screw on that carb; just the idle mixture needle and the idle stop screw. When trying to start a questionable motor, we typically open the throttle at least to 1/4 so that the idle stop is not a factor.

The M9.8B originally had an integrated siamese CD/coil, and no pulser (only exciter)... very simple and reliable... so if it was running correctly and you still have bright spark, the ignition is likely not at fault. However, you could have sheared the woodruff key that sets the timing of the flywheel to the crankshaft. You can confirm that by pulling the flywheel. To do that, you cannot pry or hammer on the flywheel; you must use a proper puller.

What do your plugs look like now? If they are too wet, there is inadequate ignition. If too dry, probably inadequate fuel.

 

[Sea Rider]

50 :1 is the right mix for that engine, the only possible way to severely foul plugs on a 2 stroke engine will be trolling with Miss Daisy for hours. Strange that 9.8 won't start with all the things you have done so far, seems a witch doctor calls for.

Have seen cases in which a blue spark was produced, but when IG tested on a spark tester was found out of specs, lacked strenght to ignite the fuel. If engine died when returning to terra firme, this could indicate a electrical related issue assuming all other systems were in opt working order.

The only way to correctly troubleshoot a working IC is with a plug tester in which you can vary the gap/lenght of electrode to check spark strenght, a min must be met in order to provide a healthy spark to ignite properly the fuel mixture. If can't get a good samaritan to help you out with a spare CD/IC unit, your last resource will be to take dead engine to dealer and have it checked there.

Happy Boating

 

[panamakid]

I think that is it a spark issue.

I have had other small engines fire up with the carb removed and spray starter squirted in to the intake side.

On this motor I get nothing.

I did a wet compression test using electric drill to turn the flywheel and both cylinders read at 140 PSI. So they are both good. The sparks seem really strong but maybe once inside the cylinder they are not strong enough.

With a flash light I can see the piston heads are black, I can rub it off lightly with a plastic soft edge tool. So I know it was running really rich.

If I buy a plug tester and it test within spec can I assume the CDI is ok?

I will do another test with new dry plugs and see if they get gas on them.

I will also see if I can get a puller to check the key.

Thanks again.

 

[Sea Rider]

Don't know for sure if a plug tester, the ones than can be bought at auto shop will do the trick determining strenght, I'm talking about the factory spark plug tester in which you can vary the spark jump and chech CD/IC condition. You have a spark, how good or bad is it, no one knows, impossible to deterrmine by visual check.

Happy Boating

 

[panamakid]

Update. Today Sunday 10/19/14 I pulled the flywheel. The woodroff key is fine. The coil and magnets on the flywheel were a bit dirty do i sanded them with a 400 gritt and cleaned well.

I got a spark tester and it test fine.

Is there any way a bearing or something could be causing resistance to where it wont allow to fire up?

so I have;

Compression 140 PSI in each top and bottom.

Spark per $10 gap spark tester that allows you to open and close gab where spark jumps

fresh gas + starter sprays

I guess I should break down and take it to the dealer.

I am afraid that the repair bill will be more than the value of the used motor.

 

[pvanv]

Do the plugs come out wet? If so, you just may be way too rich.

 

[panamakid]

It is hard to tell if the plugs were wet. They were not dripping as if they were dunked in gas. I did spray starter fluid in the cylinder holes and I think it gave a half attempt to fire. But it may have been me being optimistic.

As for being too rich, the air screw is at 1 1/2 turns out from being gently seated.

 

[Bosunsmate]

Clean the plugs. Ground the ht leads, spin it a few spins and then pull the plugs, check they are wet. Light that wetness, check it goes poff and burns straight away.
If the plugs are dry then your problem is crankcase compression. If it doesnt burn in a flash then you a getting a water leak into your fuel somewhere (exhaust gasket etc)
If the plugs are wet and they burn properly when lit with a lighter then since you would have good spark, good fuel and compression then it would indicate your timing is gone (probable powerpack failure)

 

[Sea Rider]

If flywheel rotates with no restriction whatosver, plug should do its homework specially after having cleaned the coils located under flywheel. BTW how is the magnet condition located under (side) of flywheel, has a broken missing part, magnet still is evenly attached onto body ?. Your last resource. It's called Happy Birthday Plug. Remove both plugs, should be gapped to 1.0 gap tight, feeler must not fall from plug tip.

Get a samll metal container, place a piece of cotton inside as to fill bottom shape of container, dampen well cotton with alcohol, lighter fluid, thinner, put plugs inside and ligh cotton, wait untill all the fluid has been comsumed, put plugs back on engine and pull rope, that procedure never fails specially when having a flooded carb or being at extreme cold temp.

Is not that repair will cost more than the price paid for the entire engine, see it as, lucky to find a engine at that cost and avoid to buy a brand new engine that will outcost what you paid for. Who said boating was cheap...Good luck, fingers crossed.

Happy Boating

 

[panamakid]

Would Crank Case Compression be different than the piston/cylinder compression test I have been doing?

My compression test show 140 PSI in both.

Also can water leak be a factor when I am trying to start in my garage?

I will carefully check the burn rate of my plugs and report back

Thanks

 

[Bosunsmate]

Crankcase compression is different to cylinder compression.
Low cylinder compression causes low crankcase compression but you can have low crankcase compression when you have high cylinder compression. This can be due to say broken reeds, broken seals, leak in crankcase mating surface.
I doubt that is your problem but checking your plugs get wet with fuel when plug leads are grounded (ie not causing spatkplugs too spark) will show that one way or the other.
An easier option than grounding the ht leads, if you have it, is to just pull the safety switch to kill spark while you pull the starter cord.
Water can be a factor if it has leaked in before.
On one of my motors i had an exhaust gasket leak, i fixed it but i couldnt get the motor to run. The water had got right through the motor, right through to the intake so the fuel was never able to get through the motor clean and uncontaminated so it never burnt. When lighting the wet plugs mine just burnt off slow like water, it didnt go poff instantly like petrol/oil should

My plugs sound exactly like what you are describing, thick greasy stuff on them.
Keep in mind the impellor if you are spinning the motor a lot. Dunk it in water to lubricate it every now and again

 

[Sea Rider]

My compression test show 140 PSI in both. Also can water leak be a factor when I am trying to start in my garage?

You got 140 PSI with tester, after how many pulls ?. Water leak inside combustion chamber will give hesitations even engine cutting down generally at 3/4 to wot, not when pulling rope to start as water is still in the process of going upwards. Why don't you call a Tohatsu/Merc/Nissan dealer and ask for the cost to have the complete CD/IC tested on same 9.8 model that's being serviced. Add some $$ to the CD unit cost in case was found caput and voila, you are losing too much precious boating time playing with the entire engine.

Happy Boating

 

[Bosunsmate]

So in your garage the engine can still be stuffed with water.
It takes only a miniscule contaminate of fuel by water to stop it firing.
As a baseline the wetness on the plugs should go poff as quick as it would if you dunked your sparkplug tips in your fuel tank

 

[Sea Rider]

If that engine was working ok at speed when left you stranded and being an 11 year oldie, seems you have a bad head gasket related issue, due to being out of torque, dried or hardened. Head gaskets are not eternall specially if engine has not ben retorqued after initial first 30 hours from new. Head gaskets has internal metal rings, that could be already corroded, worst if prior owner was not a big fan of flushing engine with fresh water after salt water use.

Have been through this myself, after checking IC cond which was in opt state, went straight to remove head and my gasket was rusted and hardened, no way would make a pefect seal onto crankcase. Not an issue pulling rope as long lower unit is submerged on water, those Tohatsu impellers are state of the art made, Rambo proof.

Happy Boating

 

[panamakid]

ok I put the gas tank and hose on, primed the ball. removed the safety lanyard and pulled the pull cord a few times.

I removed the plugs and touched a lighter to them and nothing...

They seemed wetish I guess, Its hard to tell.

When I put my finger over the spark plug hole and pull the start cord no gas/oil gets on my finger.

I poured a table spoon of gas into the spark plug holes, reassembled it, pull the cord and it gives a half pop.

How do I check crank case pressure? Also I did not run the hose for this so I think water in the gas would be tough.

 

[Bosunsmate]

Crankcase compression is not easy to check its more a process of elimination. Although you can tape a dollar bill over the carb and pull the starter it should get sucked in.
You describe the plugs as being wetish so obviously they have some mositure on them, if that did not disappear instantly when lit then you have water in your crankcase or fuel somehow,
If you are unusure go and do this again, use the choke if you have too to get the plugs clearly wet.
Then light it, if it doesnt go poff in an instant then your problem is clear