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5 hp two stroke problem

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Fillet1

New member
Hi all,

i have a 98 2 stroke 5 hp tohatsu that was like new and virtually unused when I bought it two years ago. Love it and it sets first pull, every time.

Been out twice this year before today and motor ran great as usual. Today I was running for about 10 minutes and the motor died. When I say died - near full throttle and it was as if I just turned it of. No sputter, rough running or anything - it just shut off. Would not restart - I'm not used to pulling the pull start more than once. After it sat for a while it started on the first pull, sputtered and died.

I pulled the carb carb when I got home and the fuel in the bowl was clean (fresh fuel) and the float was not gummed up. Pulled the plug - checked for spark and all good. From the tank to the in line fuel filter and the fuel pump all seems to be flowing - bowl was filled when I took the carb off.

Any thoughts ? I don't have a compression tester but was thinking that could be it...

thanks!
 
Clearly you ran out of either fuel or spark. An air leak from a bad o-ring in the fuel line could cause that. Also the fuel pump on the side of the carb may not be able to keep up at high speeds. If you have an ignition item such as the exciter that is acting up thermally, that could also be the culprit. Whip out your Factory service manual and check over the fuel and ignition items thoroughly.
 
Thanks Paul,

The plug has spark when I ground it to the block and pull the starter. However, the motor would not kick over at all after I cleaned the carb and even when I gave it a shot of starting spray. Is the ignition coil the most likely candidate to fail or should I be looking at the exiter or pulse coils? Can I test these from the leads on the wire harness? I am good with most things but me and multimeters don't get along. I have the service manual but it is unclear about how to specifically test each part of the ignition system.

Thanks again for for any help you can provide.
 
Ok I tested the coils. The exiter spec was 93 to 140 ohms. Mine was 121
The pulser spec was 80-117 ohms. Mine is 102.1

The ignition coil (primary) spec is .02-.38 ohms. I got 0.2 to .4

Secondary spec is 3000 to 4400 ohm. I got 6.23. So I ordered a replacement ignition coil.

I do have spark when I ground my spark plug to the cylinder and pull the starter. Would I still have spark at all with the above specs from the ignition coil?

Appreciate the help!
 
How do you back flush the power head ?

What do you need to take off or remove ?

Air or water pressure where ?

My engine is overheating and i am pretty sure there is a blockage

Thank you in advance for your help

( 40hp 402 , i think a 1979 )
 
Reviving an old thread as i have similar issues.

Engine runs well for about 5 mins then dies, might restart straight away but barely, will restart and run well after a break.

My check values very similar to above ie :

Primary 0.4
Secondary 6.41k
Exiter 121
Sensor 101

My question :

Is the secondary resistance of 6.41k indicative of a problem worthy of a replacement coil ? , spec being 3-4k.

TIA

Steve
 
Thanks for the reply Paul.

Any thoughts as to why the motor will start easily, run well for extended periods at low revs, but die if run at 75% throttle for a few minutes?

Steve
 
Further testing today.

Fuel system flows very freely, and new carb made no difference.

Today i tested the exciter for ac voltage when cranking, spec is 100-150 volts but i only got 50-60 volts.

As the 5hp motor has no electric start i removed the plug and gave repeated strong pulls on the starter handle whilst the DMM was set to record MAX voltage.

Thoughts please, is the 100-150 correct?
Is 50-60 volts typical or indicative of a ‘tired’/faulty exciter coil even though it’s resistance is in spec at 12ohms?

Tia

Steve
 
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