Tohatsu 5hp wont start!

SimonCh · 13 December 2013, 19:35

Right guys,

I've just bought a pristine looking Tohatsu 5hp 2-stroke, and the bloody thing won't start! The tank was empty so I've given it a fill of freshly mixed 2-stroke 100:1 mix. I'm getting a spark if I check against the casing and the spark plug comes out wet.

The spark isn't exactly bright, but having never tested this way before, I'm not sure what I should be getting!

Anything obvious for me to check?

Cheers

Si

spartacus · 13 December 2013, 20:41

I'll take it off your hands!

These things are bullet-proof. Check from the fuel tank, there's probably an inline fuel filter. Assuming you've checked its clean as a whistle, move onto the vent. With my Mariner 4hp, there's a vent valve on the fuel tank cap, unscrew it.

The spark, you could extract, dry it off and check the gap. Wire brush it, if it has carbon build up. Check the HT lead to it, that it makes contact with the spark plug.

Finally, assuming there's no safety cord to it, put it past 'start' on the throttle in case you've flooded it and try again. Keep us posted.

Only other thing I can think of is to strip the carb down. Straight forward and one of the things I would do on a 'new engine to me'.

SimonCh · 13 December 2013, 20:45

haha! you bloody wont! i've been after one for ages!

Vent screw open, and fuel coming nicely down the line, but havent checked a filter yet! The plug is nice and clean, but I havent checked the gap! will have a look online to see what the gap should be and try again!

Never stripped a carb down before so that will be interesting if i need to do it!

Will have a look again tomorrow in the day light!

Cheers

Si

willk · 13 December 2013, 21:12

Nice find. I can't help with the problem. FYI - the mix ratio is 50:1 - not what ails you but might help in the future if you run it at WOT as an aux.

M5B | Tohatsu Australia

PS: I'd try a NEW plug. You need one as a spare anyway.

SimonCh · 13 December 2013, 21:19

This is going to sound like a stupid question, but will the likes of halfords stock the right plug?

spartacus · 13 December 2013, 21:30

Quote:

Originally Posted by SimonCh

This is going to sound like a stupid question, but will the likes of halfords stock the right plug?

Cough!

Try Autosave (Lang Stracht), or Autoparts (Inverurie)... just watch their faces when you tell 'em it's for a Twatsoo!

Halfords are a waste of time, (apart from their Professional tools) which are the dog's danglies.

willk · 13 December 2013, 21:30

Quote:

Originally Posted by SimonCh

This is going to sound like a stupid question, but will the likes of halfords stock the right plug?

I have no idea, but the correct plug type (an NGK BPR7HS-10 or equivalent I think) should be marked in the lower interior case. I bought mine off ebay for a couple of quid.

Your manual: http://www.tohatsu.co.jp/en/boat/pro...03-11068-4.pdf

SimonCh · 13 December 2013, 21:35

Thanks all!

I'm boycotting autosave on riverside drive after they screwed me over with some filters.... Long story! Could take a run to the lang stracht though!

Thanks again, I'm not a TOTAL mong, honest!

Will call in the morning to see if they have a plug!

Si

m chappelow · 14 December 2013, 09:23

Have you tried removing the spark plug & putting half a tea spoon of fuel into the cylinder replacing plug then see if it will start then or at least fire up for a few seconds Often if an engine has been stood a while it may just need it to fire & for it to pull fuel through especialy with a single cylinder . As Spartacus said these engines are just about bulliet proof.

spartacus · 14 December 2013, 10:17

If you struggle to get the plug Simon... I have a spare one (it's used but in good nick). You can give me a shout hombre!

Locozodiac · 14 December 2013, 11:49

The gap must be 1.0 mm gap closed tight. If engine drowns in excesive fuel when trying to start repeatedly, remove plug and light it with a match and sing along Happy Birthday Plug, put it back, engine should start inmediately.

Are you using the external or internal fuel tank, the fuel/oil ratio is 50:1 not 100:1, that ratio will probably riun the entire engine specially running from medium to full throttle.

Happy Boating

SimonCh · 14 December 2013, 14:24

Thanks all! Screaming new born meant that I didn't get a chance to look today! There's always tomorrow! Shall add some more 2 stroke oil!

Sparta - I've ordered a plug off amazon, but thanks for the offer, we really must get out for a blast sometime like we keep saying!

Si

ShinyShoe · 14 December 2013, 18:01

Quote:

Originally Posted by Locozodiac

If engine drowns in excesive fuel when trying to start repeatedly, remove plug and light it with a match

Make sure you

after you've lit it in case there is any fuel or anthing else around that might go bang

Oh and do

on your insurance...

If you'd rather be safer... turn the engine a few times with the plug out. Fuel will spread over the surface inside the cylinder. Larger surface = faster evapouration. Go make a coffee... The try again...

SimonCh · 18 December 2013, 14:28

right....

I have taken the carb off, and all seems well. I split the fuel pump, and again - all seems well in there.

when i turn it over with the plug out, it throws out a massive amount of fuel!

New plug isnt any better, so really dont know where to go from here! any ideas welcome!

thanks

Si

Seabay · 18 December 2013, 15:28

I would be getting hold of a Compression tester next. Making sure the piston rings or bore are not damaged. Easy test to do. Values should be found in the manual.

spartacus · 18 December 2013, 18:23

Does it sound like it's going to take at all, as in fire into life, or does it simply refuse to catch?

Can I also check there's no safety lanyard with a Twatsoo 5hp?

It's getting fuel evidently, and you've fitted a new spark, what about air? Breather valve you've checked already and is open?

SimonCh · 18 December 2013, 18:48

not even offering to start! Kill chord is in, and i've checked the continuity, i get no reading when its connected and get continuity when the chord is out or vice versa, cant remember which, but its working anyway!

I've checked the carb and the butterfly valves seem to be working nicely

How much fuel should spit out when cranking with no plug in?

m chappelow · 18 December 2013, 21:43

How about float valve in the float chamber on the carb sticking open & not shutting off fuel when its full, Or choke not operating in the right position ?

Peter_C · 19 December 2013, 03:27

Quote:

Originally Posted by SimonCh

How much fuel should spit out when cranking with no plug in?

In reality none. That small of a motor doesn't take much fuel to run.

You might try turning the fuel off (Or pinching the fuel line closed) and putting a small shot of ether into the motor and see if it starts. Ether has just a little lube in it to protect the motor, and will fire of quickly.

Opening the throttle up takes away engine vacuum and allows a flooded motor to clear up by not drawing more fuel into itself.

PeterM · 19 December 2013, 09:57

Does sound like it's hugely flooded...?