Tohatsu 3.5 troubleshooting

[Popeye2]

Tohatsu 3.5 hp two stroke outboard for dingy.
Quit during a trip. Changed the oil and spark plug and the sea water intake is clean. Still will not start.
What would be the next few things for me to check?

[ThereAndBack]

Drain the carb and look for water in the gas. Also clean the carb. I had a 3.5 and it was awful how often the carb had issues. It got to the point that I could take the carb apart without actually looking at it.

[bensolomon]

Silly things.....fuel cutoff in the on position? Is the air vent not obstructed and open? Choke adjusted appropriately?

After that, order a new carb. It's what I did for my 3.5.

[stormalong]

How do you change the oil in a two stroke?

I agree with ThereAndBack, Cleaning the carb on my Tohatsu 3.5 is an annual ritual. Running the carb dry when laying up the engine helps - turn off the fuel valve and let the engine run until it dies. And only use ethanol free fuel.

[Popeye2]

Originally Posted by stormalong

How do you change the oil in a two stroke?

I agree with ThereAndBack, Cleaning the carb on my Tohatsu 3.5 is an annual ritual. Running the carb dry when laying up the engine helps - turn off the fuel valve and let the engine run until it dies. And only use ethanol free fuel.

Changed the gear oil. Looked fine. Ok will start to look into the carb. Thanks.

[RickG]

We had a problem with our new to us Tohatsu 3.5 starting. I took the cowling off and the brass screw that the needle valve went through had backed all the way out. I screwed it in and it started running again fine.

Cheers, RickG

[GordMay]

ENGINE FAILS TO START
1. Check level of fuel in tank
2. Check air vent screw on tank open
3. Check arrow on primer bulb to ensure fuel line is connected the right way
4. Check fuel lines connected tightly and bulb primed
5. Check engine is in neutral and throttle control in START position
6. Inspect battery and connections (electric start)
7. Check emergency-stop (kill) lock plate connected correctly to switch
8. Inspect fuel filters (fuel tank, external, internal) and clean if necessary
9. Check internal fuel filter to ensure filter casing is tightly screwed
10. Inspect spark plugs and clean if necessary
11. Check fuel pump to ensure membrane is not torn out
12. Check carburetor to ensure that draining screw is not opened

[captd44]

#1. Is there spark at the plug while turning engine over?

[Popeye2]

Originally Posted by captd44

#1. Is there spark at the plug while turning engine over?

Will look into that. Thanks.

[capt jgw]

I have that same motor under the Nissan brand. Had a problem where it would run for a while then quit, the faster I ran it the sooner it would quit. Fuel valve open, cap vent open. As a last resort I ran it with the fuel cap off, and it didn't quit. Took the cap apart and found a rubber diaphram with two tiny holes in it that were plugged. Cleaned them out and no more trouble.

[Reefmagnet]

Has it got a safety lanyard? Check the switch hasn't failed.

[Compass790]

Originally Posted by Popeye2

Tohatsu 3.5 hp two stroke outboard for dingy.
Quit during a trip. Changed the oil and spark plug and the sea water intake is clean. Still will not start.
What would be the next few things for me to check?

If no spark check kill switch, often they get a bit of moisture in. Always use a filter funnel & fit an inline fuel filter if you can. Saves a lot of carb cleaning. Little outboards have tiny jets & it doesnt take much to block them.
See if your plug gets damp with fuel if you have spark when cranking with choke on & no throttle. If plug doesnt get damp you haven't got any fuel coming thru. Then you need to check float valve & clean carb.
Dont fill your tank on a beach when sand is blowing all over the place. I can't believe how many outboard tanks have sand in them.

[Popeye2]

Originally Posted by captd44

#1. Is there spark at the plug while turning engine over?

I changed the spark plug. Engine working fine now.
The spark plug i took out was only two months old and was black with sooth .
Engine not used much
Pehaps it will happen again?
Clean the carb?
Would incorrect mix of oil in the petrol cause this blackening? Seemed like oil around the plug.

[tkeithlu]

Was the plug wet or just sooty? Wet could be from failed tries at starting. Soot sounds like too rich a mixture but could be rich starting (choke) mixture that partially burned. Clean that plug, get it started, and adjust until you get a running engine with a dry brown plug.

[capt jgw]

Originally Posted by Popeye2

I changed the spark plug. Engine working fine now.
The spark plug i took out was only two months old and was black with sooth .
Engine not used much
Pehaps it will happen again?
Clean the carb?
Would incorrect mix of oil in the petrol cause this blackening? Seemed like oil around the plug.

Could be. Mine runs like crap if there's too much oil.