Why would my motor just stop

[kevinwd1]

I took my boat out today for the first time in about 4 weeks .I put fresh fuel in and outboard (25hp 2006 Tohatsu) and it was pumping plenty of water. I had been going for about 1hour with a few stops when suddenly while at WOT the motor just stopped. It didn?t miss, or seem to run out of fuel it just stooped as if it had no spark. I put the motor back in to neutral and it stared first pull and I had no more problems with another 30 minutes of use at WOT. Why the motor would stop like this and is this an indication of some sort of electrical problem?
​
Regards Kevin

 

[robert graham]

Sounds like a fuel restriction caused by your fuel tank vent not being open.....if tank vent was closed or plugged up motor might quit at higher RPM's like you describe....

 

[redneck joe]

but would it quit suddenly or bog down - even for a second. Does sound like electrical but that is totally not my area.

 

[pvanv]

Year doesn't really help us understand what motor you have. Tohatsu motors are identified strictly by model/serial, not year of manufacture.The stopping could have been almost anything... from a flaky/intermittent wire, to a bit of crud that jammed in the carb for a second. I would verify proper fuel venting, andf carefully inspect the wiring, especially the brown stop wire. If you can never duplicate the problem, and cannot find any issues that might have caused it, it will remain a mystery.

 

[gm280]

There are so many reasons that an engine can be running fine and then stop. So without further info, I'm not so sure anybody could make a rational pin point answer to the actual problem. It could be fuel flow issues, electrical problems, air intake, bad ignition parts, timing problems, carb issues, over heat problems, tank problems, fuel pump, primer bulb, spark plugs, and the list could go on for a while. I know that I can't point to the problem with what you posted. I'd either need to be there and do my trouble shooting procedures OR, you need to state more info after you test things. Can you provide more info, like the actual conditions and what you did or didn't do to the engine recently? IDK JMHO!

 

[robert graham]

but would it quit suddenly or bog down - even for a second. Does sound like electrical but that is totally not my area.

Nope, it'll quit right quick....like a light switch. Run the motor at say 75% wide open for a while, then gradually increase throttle towards the 100% range and listen for it to shut down quick. If it doesn't do it again during this test then you may have another issue.....check your tank vent....You don't happen to have one of those new government ventless gas tanks do you?....if you do then crack open the cap just a bit while running....

 

[kevinwd1]

The motor is a two stroke M25C3 .The fuel tank was well vented with cap lose as vent tends to vibrate closed .I?m assuming these motors don't have safety cut-outs due to over revving or overheating? It just seemed strange for the motor to go from full power to nothing instantly and then start first pull with no other problems running at WOT for another 30 minutes. Must have just been a bit of crap going through carbie?

 

[pvanv]

Perhaps. If it happens again, try to get very specific, and we may be able to provide some more insight. No your model does not have an ESG for overheat.

 

[Sea Rider]

Is the inttermitence still going on each 30 minutes ? If so, could be a electrical related issue, component warms, shorts, misses and the story goes on. That model doesn't have a rev limiter nor a overheat system.

Happy Boating

 

[kevinwd1]

Sorry Sea Rider I didn't explain myself very well.I ran the motor for another 30 minutes after it stopped just to see if it would do it again but it ran fine .So I'll file this incident under M for mystery

 

[Sea Rider]

Kewinwd1

If you won't be using your engine let's say for more than 1 week, while engine is being water flushed, disconnect engine fuel hose and let engine die. That's the best way to keep carb not clogging itself with 2 stroke oil remains, specially when gas evaporates.

Usually let my engine die after earch outing, as don't know when will be my next one. It's good to consume fresh fuel as far as possible, specially if gas has not been aditive treated. E fuels gan go bad in just days..

Being a 9 year oldie, would advise to run an overdose of Power Tuner Decarbonizer through carb throat, follow can instructions, really does wonders restoring lost power on 2 stroke engines, highly recommended product. Should be used every 100 worked hours to keep engine runing like a champ.

Happy Boating

 

[kevinwd1]

Thanks for all the feedback guys.
Sea Rider I was told that it?s not a good idea to run a two stroke out of fuel on a regular basis due to lack of lubrication?
I had a look online for decarbonizer products here in Australia but couldn?t find much. If anyone knows of a good product that I could buy here in Australia that would be appreciated.Also do these motors run alright if the thermostat is removed? The motor is always run in salt water and is well flushed after use but I still think that the thermostat is very prone to clogging from salt build up. As I live in the sub tropics with water temp never getting below 19 Degrees Celsius (66 degrees Fahrenheit) do I need one

​Thanks Kevin

 

[Sea Rider]

Was told that it’s not a good idea to run a two stroke out of fuel on a regular basis due to lack of lubrication? Also do these motors run alright if the thermostat is removed? The motor is always run in salt water and is well flushed after use but I still think that the thermostat is very prone to clogging from salt build up.​

Kevin, fuel/oil mixed at 50:1 ratio has sufficient oil for engine to run untill drops flat dead, been doing this for 20 years with no issues. Thermo controls to achieve correct working temp on the powerhead speciallyl if boating on cold waters, don't know about boating on hotter waters without a thermo. Paul probably will have a correct tech answer for this one.

If you flush your engine inmediately after salt sea use, no issues about thermo or water cooling passages being clogged. Just happened to remove mine after 2 continuous years of use, that's 300 metered hours, to my complete surprise, thermo came out 95% spotlessly clean. Just needed a brush off with plain vinegar and back in along new thermo gasket.

Happy Boating

 

[Star]

Not the same motor, but for what it is worth, I had 2 isues that caused this on a 4 stroke 15 mercury. Fuel line liner delamination restricting fuel starvation. Motor would start right up right after. The second problem was after 45 minutes of WOT it would studded and buck and sometimes die. After two years of scratching my head it finally dropped one cylinder for 10 to 15 seconds!!! I had tested coil resistance and other components It was OK. Replaced the Yammy coil (cheaper than Mercury) It has been fine all of last season. The motor would also start right up after. The first problem I replaced the bad silver fuel line and bulb from mercury.

 

[Sea Rider]

Had exact same hose issue with a 2 stroke 5 HP Mariner. The hose was a 2 part hose. The inner hose was very bad quality, broke in tiny pieces and clogged bulb and fuel pump. Broke my brain for several days. Got rid of the interior hose and used just the ext one, still working that way.

Happy Boating