New Tohatsu 3.5 HP (MFS3.5C) Won't start after it's warmed up.

[111torrance111]

Have a new Tohatsu 3.5 4 stroke motor for a Dinghy, it's starts easy when cold and seems to warm up okay. Once we're under way and decide to stop it won't restart, very frustrating as it's so easy to start when cold.

Open gas valve/open fuel tank air valve/choke, we leave the choke out until the engine rev's ups and then push in (Off) all the way. Can continue to run for quite a while, but once we stop nothing seem to get it restarted. On the throttle handle there's a position that says "Restart" always tried that first, then get into trying the choke and pull/pull/pull with no results.

any suggestions would be appreciated.

Thanks/Jerry

 

[Sea Rider]

Does the choke knob have a middle position between fully closed or opened ?

Happy Boating

 

[111torrance111]

Does the choke knob have a middle position between fully closed or opened ?

Happy Boating

it does, tried different positions. I can try again just to confirm.

 

[Sea Rider]

2-4 stroke outboard motors cools very fast compared to automobiles and some times turns difficult to instant restart. Try : With throttle grip remaining at min, pull choke knob fully out, pull rope 3 times, push choke fully in, rotate throttle grip to start position, pull rope till starts....

Happy Boating​

 

[MattFL]

Alternatively, hot 4-strokes flood easily. If it's still hot when you're trying to re-start it, try no choke and opening the throttle half way or all the way while you're pulling the rope, just be ready to turn it down the moment it starts.

 

[Sea Rider]

When at a stop for some time and the motor is still warm, placing the throttle grip to the start position and pulling the rope hard should start the motor right up. But once has completely cooled down it's a different scenario. Some motors get tricky to start untill you learn what they like to be fast started.

Happy Boating​

 

[tbetty]

Hi- 111T, if you get that hard start problem figured out be sure to come back and post up. I have the same problem on a merc/tohatsu 3.5 no
permanent solution yet. It does seem like it is too rich as it sometimes starts when throttle is opened all the way.

 

[pvanv]

Yes. Easily flooded. Don't use choke for restart. Open throttle for lots of air. If still fails, pull the plug. If wet, flooded.

 

[Sea Rider]

If the spark plug is found extremey wet, heat it up with a lighter, screw it back in the head and without choke restart the motor as per the Owner's Manual, should start inmediately. Spark plugs should be cleaned and regaped periodically for easy starts and restarts...

Happy Boating​

 

[tbetty]

Thanks to both Paul and Sea Rider. I will play with it some when weather warms up. Still too cold for this Fl boy to get wet.

 

[111torrance111]

Hi- 111T, if you get that hard start problem figured out be sure to come back and post up. I have the same problem on a merc/tohatsu 3.5 no
permanent solution yet. It does seem like it is too rich as it sometimes starts when throttle is opened all the way.

Never really solved the problem, but after trying all the different suggestions listed here it just seems finicky. However the best solution so far has been to loosen the gas cap a little bit, it seems to restart much easier, I'm assuming the release valve on the built-in tank isn't enough air for the warm restart.
If we find something different I'll reach out.

Jerry

 

[tbetty]

Thank you 111torrance, will try that next time I have it out.Considering
moving up to electric start and hp. I haven't seen any el-start under 9.9hp. thanks again tb.

 

[MattFL]

Never really solved the problem, but after trying all the different suggestions listed here it just seems finicky. However the best solution so far has been to loosen the gas cap a little bit, it seems to restart much easier, I'm assuming the release valve on the built-in tank isn't enough air for the warm restart.
If we find something different I'll reach out.

Jerry

Usually as gas gets warm the pressure inside the tank will increase. When you loosen the cap, can you tell if there's pressure or a vacuum? That brings up another idea, depending on the fuel you're using and IF the tank is under the cowling with the motor, maybe you're getting vapor locked?

 

[km1125]

I'm wondering if you have one of those new tanks that don't vent until some higher pressure is achieved. This might cause the engine to flood after being shut down. Perhaps you can try and leave the cap on the tank loose, so it won't develop vacuum or pressure and see if that makes a difference. You can also try and hold the throttle wide open on the first pull when you try to restart under hot conditions (just be ready to pull it back to idle quickly if it does!)

 

[Sea Rider]

New Epa fuel tanks will vent when a certain PSI is achieved inside the tank, should not flood the motor with fuel as there's a Fuel Demand Valve located right in middle of the fuel connector and bulb that prevents that condition to happen.


Anyway chek if operating the motor with the tank's pressure relief valve partially open betters the described situation...

Happy Boating​

 

[MattFL]

Does the little 3.5HP not have the tank under the cowling like the 6HP does?

 

[Sea Rider]

Does the little 3.5HP not have the tank under the cowling like the 6HP does?

Yep has an internal one liter fuel tank under the cowl. The tank's air valve must remain fully opened during motor operation...

Happy Boating

 

[km1125]

New Epa fuel tanks will should vent when a certain PSI is achieved inside the tank, should not flood the motor with fuel as there's a Fuel Demand Valve located right in middle of the fuel connector and bulb that prevents that condition to happen.
​

FIFY, but it doesn't sound like that's related to the OP's issue anyways with his internal tank.

 

[Sea Rider]

FIFY, but it doesn't sound like that's related to the OP's issue anyways with his internal tank.

I'm wondering if you have one of those new tanks that don't vent until some higher pressure is achieved. Then why did you mentioned those type of tanks in post 14 when you didn't know if the OP's motor had an internal fuel tank or not. Was just the tech explanation of those EPA tanks which most don't have the slight idea on how they work jumping to false assumptions along too much writing which is beside the point with reference to them...

Happy Boating​

 

[km1125]

I'm wondering if you have one of those new tanks that don't vent until some higher pressure is achieved. Then why did you mentioned those type of tanks in post 14 when you didn't know if the OP's motor had an internal fuel tank or not. Was just the tech explanation of those EPA tanks which most don't have the slight idea on how they work jumping to false assumptions along too much writing which is beside the point with reference to them...

Happy Boating​

Right there at the beginning of the sentence where it says "I'm wondering" means I don't know but there's a possibility. The OP could say (or even just think) "well, that doesn't apply to me" but if it did he'd have one more thing to check. Those tanks SHOULD relieve pressure if they're working correctly, but when you're having problems then SOMETHING isn't working correctly. Just like on an inboard that has fuel tank vents... they SHOULD relieve any vacuum in the tank, but if those vents are clogged or not working correctly they will likely stop the engine from working correctly at some point.