Tohatsu 9.8 HP Revival.-

[Sea Rider]

This 2 stroke 9.8 HP motor in a terminal condition was sent to me prior being used as an anchor to see if was possible to revive it so accepted the challenge as have never before worked on a 9.8 HP. What was found :

The carb was found in such an internal mess that would have been very difficult for the motor to start, the jets were highly corroded, all the tiny holes were clogged, had to guess where the tiny holes were located, a haute couture needle made the trick, now cleaned to perfection. Wrong B7HS cold spark plugs gaped to 0.8 mm when the 9.8 calls for BPR7HS-10 gaped to 1.0 mm. Motor lacks a T-Stat, a shade tree mechanic removed it moons back, there’s the stupid idea down here that a marine motor without a installed T-Stat will work much better which is a total fallacy. With sea water at 15C how can a motor work efficiently. Pics speaks for themselves...

All electrical components terminals were found blackened, now shinning as when new. The spark tester confirmed the Ignition Coil lighting very strong and healthy. The water pump works fine but without a T-Stat the peeing port and the T-Stat port exits too much water cooling the motor excessively which is bad as will carbon up the combustion chamber and pistons much more in the short run. After half an hour running geared on muffs swiped my tongue on the exhaust cover without any issues.

Cold Cylinder Compression Test dialed 75 PSI even on both cylinders after 5 hard rope pulls. The motor underwent a light CRC decarbonization. Tomorrow will continue with a longer one. It’s a great idea to drill a 2mm hole right in middle of the air silencer, that way can squirt any time CRC decarbonizer with provided cannula directly through the neck without needing to unbolt the carb or the silencer whichever applies.

Happy Boating​

 

[pvanv]

Good job. If no stat available, could at least install a restrictor plate for faster warmups.

 

[Sea Rider]

The second long CRC carbon remover application through the drilled hole did an excellent job, now the motor runs geared on muffs much smoother than before. One story is running on muffs geared, other one pushing a boat on water.

Although the motor can run with no issues at full grip, when at idle the motor tends to die, have adjusted the pilot screw to no avail. Although the carb is immaculate clean the corroded jets, main nozzle could make for this to happen, was wondering if the shade tree mechanic has fingered the time advance, this motor doesn't have a timing plate with 5º marks as to check the correct time advance/carb snych as possible to do on 9.9 to 40 HP larger HP motors.

With one up the motor takes bit long to plane a 3.80 Mtr Sib, a factory delivered prop it's not the way to go with a portable motor. next week will install an induction tach, go for a wot run and check max achieved rpm and afterwords a prop hub slip test. Other down issue is the motor is a long shaft powering a short shaft Sib, too much lower leg drag along side water splashes that slows the Sib down.

The motor is loosing water and smoke at the lower base gasket, seems that will need to tear the whole crankcase and change it along the exhaust, and cylinder head gaskets as well.... The motor without a T-stat pees excessively as a mini waterfall which is bad....​

Happy Boating

 

[raczekp1]

this water flowing down from upper midsection is water that flow out from powerhead after cools dowm powerhed . no need to tear dowm powerhead

 

[Sea Rider]

This motor with removed thermostat will be eternally cooling down, a tree shade pseudo mechanic removed it moons back. The middle hole located in the upper mid section it's the thermostat peeing port. When the thermo is closed during wam up time the amount of water released is scarse, when opens up the amout is highly increased, but not to the amount seen on previous pic...

Tearing down a powerhead does not means that needs to be split opened, remove the crankshaft, pistons, etc. This motor needs desperately new OEM base, cylinder head and exhaust cover gaskets...

Happy Boating​

 

[Sea Rider]

Measured with a caliper vernier both Time Advance Link Rod and Pilot Screw factory settings from a 2 stroke boxed 9.8 Tohatsu motor. TALR is 22 mm and PS is 10 mm. Tomorrow will check if the shade tree mechanic has played with the time advance setting, if so, will need to be restored to the factory setting.

The motor operator says that when the motor runs with attached cowl tends to shuts off when the throttle grip returns to idle, doesn't happen when the motor runs with cowl removed. Read in Iboats forums that this issue is happening in other brand motors. Ain't that strange, will probably need to call the Witch Doctor..

Happy Boating​

 

[MattFL]

Maybe the pilot jet is set a little rich? When the cowling on, it's going to hold heat and the air going into the carburetor will be hotter than without the cowling. Hotter air needs less fuel. Just taking a guess since that is an odd one.

 

[pvanv]

Smoke from the base gasket can choke off the motor. With the cowl off, that just wafts away.

 

[Sea Rider]

Smoke from the base gasket can choke off the motor. With the cowl off, that just wafts away.

Thanks Paul, missed that one, first time seeing a motor running as such, definitely the lower crankcase is smoking not heavily though along squirting water at the pan, with reason the issue is canceled when the cowl is removed. What's the use of the Red Silicone for, definitely not right to seal back a cylinder head or exhaust covers ? What's the name/model of the Electronic Vacuum Gauge, the ones with 4 LCD lights.? Merry Christmas!!

Happy Boating​

 

[pvanv]

Do you mean a carburetor balancing gauge set?

 

[Sea Rider]

Do you mean a carburetor balancing gauge set?

Yep to balance and set all Pilot's Screws for each carb to idle top.

Happy Boating​

 

[Faztbullet]

Darn near impossible to use on a 2 stroke motor

 

[Sea Rider]

Darn near impossible to use on a 2 stroke motor

Will depend if the manifolds or carbs have the vacuum ports to screw the vacuum nipples on higher 3-4 carbed 2 stroke HP motors. Useless for single carbed 2.5-40 HP portable motors. This is the Vacuum Balancer was looking for :

​

Happy Boating

 

[racerone]

The video shows the gauge used on a ----4 stroke motor------Hard to use that unit on a 2 stroke !!!-----It seems some folks insist that this procedure can be / should be done on a 2 stroke.----I do not know why that is so !

 

[Sea Rider]

The video shows the gauge used on a ----4 stroke motor------Hard to use that unit on a 2 stroke !!!-----It seems some folks insist that this procedure can be / should be done on a 2 stroke.----I do not know why that is so !

The video clearly states being a 4 stroke motor, was referring to the vacuum balancer brand and the procedure used. Dislike going per the archaic wagon method of counting the number of in-out turns when balancing the Pilot's Screw specially if a tree shade mechanic that abound down here has already fingered all the Pilot's Screws.

Happy Boating​

Happy Boating

 

[racerone]

I believe you mis-understand the concept of this vacuum gauge.----It works on 4 stroke motors.----It is not used on 2 stroke motors !!

 

[Sea Rider]

I believe you mis-understand the concept of this vacuum gauge.----It works on 4 stroke motors.----It is not used on 2 stroke motors !!

Sorry, not being used on 2 stroke motors doesn't mean that can't be used to measure/adjust vacuum readings on any 2-3-4 carbed motors. For that to happen must meet these requirements :

Somewhere to connect it. The connection will either be a blanked off screw hole or a stub for pushing on a rubber hose. Most two-strokes do not have any connection points. In such case you can drill a threaded hole at the middle manifold and close it with a cap screw, remove it and install the Carbtune nipples and rubber tubes and that's it. For 2 strokes use the vacuum readings are somewhere 0 cmHg to 40 cmHG.

This pic is a prime example of a 2 stroke Yam 85 HP motor which all 3 idle Pilot's Screws has been fingered by a shade tree mechanic. Were found as such after being height measured with a vernier caliper. Plug (1) which corresponds to the upper carb runs excessively rich compared to the second/third plug which runs much less rich. Those 3 plugs have at the most 50 run hours from brand new.

Carbtune was developed in UK for motorcycles tune-ups and latter for cars and outboard motors usage.

Happy Boating​

 

[pvanv]

Yres, the Carbtune will work.

Morgan Carbtune - carburetor synchronizer for balancing motorcycle carbs

Carbtune motorcycle carburetor synchronizers;polycarbonate tool pouchs;for motorcyclists

www.carbtune.com

 

[racerone]

?---Throttle plates are CLOSED at idle.-----And on many 2 stroke outboards there is a balance passageway between carburetor throats / cylinders.----How does the --" super tuner " ---deal with that?

 

[Faztbullet]

From the Carbtune site....