Help with my first outboard motor please!

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nexus180

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Hi all - I am new to boats and at the moment I have a small rib on which I have a Tohatsu 4 stroke outboard. I have come to take it out of the shed after this winter and found that the fuel cap vent screw was left open over the winter. I have tried to start the motor (on reflection maybe I should not have even done that?) and it will not fire up. Am I right in thinking that the probable cause here is that moisture will have got into the tank over winter - so I have water in my fuel? If so, is the best course of action to drain the fuel (I've read some people suggesting draining by turning the motor upside down in these circs?) and replace it with fresh fuel?

Any help greatly appreciated!

Luke
 
Yes the petrol would have evaporated a bit making it no good anymore. Best to drain the tank...if you can take off the carb float bowl and clean that..new petrol and she will fire straight up.
 
Yeah,
Turn the thing on its side (the correct side so oil doesn't drain too) and drain the fuel. Then crack open the drain screw on bottom of the carb bowl.
Best practice is apparently to shut the fuel valve and run it out of fuel at the end of use. Stops the fuel going off in the carb and making a mess of the jets etc.
good luck
 
A good carb clean and nice new fuel and I am sure she will fire up as others have said........... Good luck and good boating

Dennis
 
Thanks for all the suggstions - I have drained the fuel, dismantled the carb and cleaned it out with carb cleaner, plus replaced the spark plug for good measure - all to no effect; the motor doesn't even cough or splutter like its about to start. I contacted the people who fitted the new carb on it last summer to see if they had any ideas; unsurprisingly their suggestion was a one line "bring it in and let us repair it" - which I am loathed to do as it is a new carb that I have not used since new! Does anyone have any other suggestions of things I might try first?
 
did you extract the jets and inspect to see if gunge had blocked them ? Carb cleaner is a a solvent which may not deal with insoluble lumps of crud.


I'd also look at adding a petrl improver such as Briggs and Straton fuel stabilsier

https://shop.briggsandstratton.com/us/en/parts-and-accessories/fuel-additives

USA site I know, but also available freely in the liberated UK. Excellent stuff, we use it in all small petrol engines from chain saws to o/boards to counter the pernicious effects of ethanol.


Oh yes, did you use really really fresh petrol ?
 
Does the plug spark? Is there a 'sniff' of fuel from the cylinder after you've tried to start? If you've both, then it's probably the quality of the fuel. If you're missing either, then clean the plug, or clean the jet. Good luck, it'll be OK.
 
Thanks again for the suggestions, in relation to which:

1.when I took the carb apart I noticed its a slightly different design to the original one (it has "Kaisha" or similar engraved on it, in case that is significant) in that the position of the secondary jet (probably not what its called) is different. the main jet is in the same position in the centre of the carb chamber; I took both parts of that out and it did look a bit gunked up - but after the carb cleaner I could see straight through. The secondary jet on my original carb was sticking out of the top side, outside edge of the carb and I unscrewed it from the outside to remove it. On the current carb the secondary jet is strangely set on the left hand face of the carb (as you look at it when it is mounted - ie the face of the carb that attaches to motor, rather than to the air filter side) and is sunken into the carb body. It was screwed in so tight that I was not able to actually remove it - so I could only spray carb cleaner down from the outside. I'm guessing that could mean that that jet is still blocked, so I should try again to remove it (I'm just concerned about fouling it with the screw driver as its brass and fouled jet screws by previous owner were the reason I had to replace the last carb)?

2. I've got fuel stabiliser that I've used in the past. After draining the stale fuel from the tank/ carb, I replaced it with fuel fresh from the pump.

3. before I dismantled the carb I drained the old, stale fuel out - first from the top of the fuel tank then by opening up the drain screw on the bottom of the carb. In case its relevant, despite doing this I did notice that when (after cleaning and rebuilding the carb) I disconnected the pipe that runs from the fuel switch to the carb it was still full of fuel - thinking about it would that not mean that when I tried to start the motor, the old (stale) fuel that was sitting in that pipe would have been sucked up into the carb? If so, presumably if I try to restart it now, having drained that pipe, it might work?

4. I have a dive bottle of compressed air, so I guess it would not harm to give the jet/s a blast with that?

5. re the spark plug - I simply took the old one out and stuck a brand new one in there. I have got a spark plug gauge that I could check the spark plug with, but presumed it would be OK as its brand new. I don't know how to check whether the plug is sparking - unless you mean does it sound like the motor is trying to start/ spark up when I pull the starter cable? The only thing I can liken the sound of it to when I pull the cable is when you try to start a petrol hedge trimmer and have to pull the cable a few times before it starts - so if that is the sound of a spark plug sparking, then yes - the plug on the motor seems to be sparking!

By the sounds of things I really need to get that secondary jet out and clean it - and hopefully either that or my draining the remaining stale fuel out of the pipes will fix it?
 
You state "your first outboard", we have been their :(.

so have you1st checked the safety cut out switch? Tohatsu have a much fatter token than others, also the Tohasu switch is normally closed and inline with the coil primary, where most are set to short circuit when 'opened' buy pulling off the emergency lanyard.

I use carb cleaner then blow jets out with compressed air cans, using the tube pushed tight against the holes. Early days i used a car or bike tyre pump with the connector end cut off.

Holding the jet in a fine cloth like curtains net can prevent launching the jet into the neighbours garden - 3 doors down.

Trsting for spark can be tricky while simulatiously pulling the starter chord, you need to get the body of the plug against the engine, pull the chord while watching for a spark - best done in a shaded place or garage.

Advice could be more accurate mentioning make and model.

Alan
 
Hello again. Just taken the carb apart again and managed to remove the little "secondary" brass jet to clean it - but it was absolutely spotless, so that's not the cause of the problem sadly. Whilst I was there I checked the height of the carb float which also seemed fine.

As suggested, I have tried to check that I am getting a spark off the spark plug (having confirmed the gap is OK) and at the moment I can't see a spark. It was tricky testing it with one pair of hands so I plan to do that again later when my other half is about - but if there's no spark, what do I do next??

I've also looked at the cut off button and tried holding it as far out whilst I try to start the engine - no joy.

I'm running out of ideas I have to say. The only other thing I noticed today was that when I opened the fuel drain screw at the bottom of the carb to let the fuel out, not a drop came out (I tried it with the fuel supply on and off), even though there was about 2cm of fuel left in the fuel tank - is that normal? I also noticed that the little plastic filter on the fuel line in to the carb (hopefully you will see it on the pic) only had a dribble of fuel in it at all times - when common sense (dangerous I know) would suggest to me that it should presumably be full of fuel when the fuel starts flowing up the pipe into the carb?). I will try to attach a pic of the carb set up, in case anyone can spot anything obviously wrong!

Oh - and its a Tohatsu 3.5 4 stroke 2007.
 

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You can clean the carbs till the cows come home on those 4-strokes, they still won't run right. The Toh/Merc/Mariners are well known for it.

Take the jet out, bin it, and fit a new one. Job jobbed.
 
Even with a brand new carb?? It was fitted brand new at the end of last summer when I brought it home, started it to check it worked and have not started it since.
 
Are you sure the fuel is getting through from the tank. Fill the tank and remove the outlet pipe from the carb and turn on the fuel and see if it flows.

Also on the spark test it in a dark room or at night.

Dennis
 
nexus180 said:
Hello again. Just taken the carb apart again and managed to remove the little "secondary" brass jet to clean it - but it was absolutely spotless, so that's not the cause of the problem sadly. Whilst I was there I checked the height of the carb float which also seemed fine.

As suggested, I have tried to check that I am getting a spark off the spark plug (having confirmed the gap is OK) and at the moment I can't see a spark. It was tricky testing it with one pair of hands so I plan to do that again later when my other half is about - but if there's no spark, what do I do next??

I've also looked at the cut off button and tried holding it as far out whilst I try to start the engine - no joy.

I'm running out of ideas I have to say. The only other thing I noticed today was that when I opened the fuel drain screw at the bottom of the carb to let the fuel out, not a drop came out (I tried it with the fuel supply on and off), even though there was about 2cm of fuel left in the fuel tank - is that normal? I also noticed that the little plastic filter on the fuel line in to the carb (hopefully you will see it on the pic) only had a dribble of fuel in it at all times - when common sense (dangerous I know) would suggest to me that it should presumably be full of fuel when the fuel starts flowing up the pipe into the carb?). I will try to attach a pic of the carb set up, in case anyone can spot anything obviously wrong!

Oh - and its a Tohatsu 3.5 4 stroke 2007.
Click to expand...

You are clearly not getting any fuel flow to the carb!

Check by disconnecting the hoses ( You'll have to cut the cable ties off so get some replacements first) untill you find out why.

Is the tank vent open and clear ?

Is there enough fuel in the tank?

is the fuel tap opening properly?

if you can get a flow from the tank and through the filter to the carb then suspect the carb float or float valve is sticking ....Did you refit the little clip on the needle valve to to the float arm when you reassembled the carb.

Once you have fuel getting into the carb, return to checking the spark if still no joy ... it should jump best part of a cm.
 
Last edited:
Everyone concentrating on fuel when he has not yet confirmed he has a spark! I would firs make sure you are getting a spark, then move onto fuel.... Have you checked connections are they all clean to coil etc and HT leads OK?
 
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