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Old 08-05-2020, 14:17   #1
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Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

I have a four year old 18hp Tohatsu 2-stroke. It has always started on the 1st or 2nd pull, idles a little rough, but otherwise runs well... until yesterday. I hadn't run it in a month or so, so I put fresh ethanol free gas+oil in the tank and took the dink out just to exercise the motor. Ran fine at moderate throttle settings for 10 minutes or so, then ran it about 2 minutes planing at WOT (Italian tune-up). When I slowed back down, it ran fine for about 15 seconds, then started to stumble. It sounded like it might be fuel starved, so I checked the fuel bulb (wasn't hard, but definitely had not been sucked flat) and gave it a gentle squeeze, and engine died ~immediately.

It refused to restart. Unscrewed fuel tank cap just in case it was under vacuum, still wouldn't start. After getting towed back to the slip, checked fuel hoses and filter, found nothing obviously wrong. After lots of pulling, 30 minutes later, engine finally started and ran normally. I convinced myself it must have been a kinked fuel hose. So...

I stupidly took it back out for another test run, and exact same thing happened. Ran fine for 10 minutes, then 2 minutes at WOT, then sputtered and died again. Checked all of the same stuff, and finally got it started again 20 minutes later, whereupon it ran rough, but ran well enough to get back home.

Today it runs fine. Tied up to the dock, runs at WOT and any other throttle setting, and never dies (of course it doesn't hit the same RPM at WOT while tied up to the dock). I'm puzzled. What would cause it to die, and not want to restart, after a short WOT run?

Jeff
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Old 08-05-2020, 14:30   #2
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

When it died, were you able to check to see if you had spark at the plugs? Was there fuel in the carb/bowl?
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Old 08-05-2020, 14:58   #3
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

How's the cooling water flow? sometimes when a 2 stroke overheats it gets hard to start. We had a similar problem when water galleries got clogged with jelly like marine life.
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Old 08-05-2020, 15:17   #4
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

Our 9.8 had this problem. As Compass790 says, check temperature. On ours the pee flow was just fine, but flow through the engine was restricted. Remember it was at the back side of the engine where the cooling water comes out, but don't recall if it was the t'stat cover or something else. Gallery there down to a pinhole, even though we good flow through the indicator.
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Old 08-05-2020, 15:27   #5
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

@Bill O: unfortunately I couldn't check for spark or carb / fuel delivery when it died... no tools on hand (dumb), and concentrating on getting a tow (upwind) to the slip. I was hoping to duplicate the problem today so I could test spark and fuel, but now can't get the danged thing to die.

@Compass790: There's water coming out the telltale/pee hole, but I guess flow could still be restricted/insufficient. I understand that could cause hard starting, but would it cause a running engine to stumble and die?

Additional information... spark plugs are relatively new, and were checked/gapped a month ago. Fuel tank is newer EPA tank with the stupid vent cap, but taking cap off doesn't seem to make any difference.

I'm a little suspicious of the fuel hose. It's about 1yr old and is the thin gray type with clear plastic liner. I just cut one end off to freshen the connection at the tank end, and looks like the liner might be collapsing (or maybe it just looks that way because I just squeezed the line with shears to cut it). There was an amber colored gel/grease looking substance between the gray outer hose and the clear inner liner. Is that a common problem with these hoses?
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Old 08-05-2020, 15:34   #6
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

Yes, as the engine overheat it dies. With some water flow it will run low for quite a long time, less at WOT. And then when you re-start (after it cools) it usually won't run as long because it is already warm. Next day, after full cooling, it seems OK for a while.

Amber deposits are usually gasoline - unusual in a hose not that old.
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Old 08-05-2020, 15:38   #7
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

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Originally Posted by Dsanduril View Post
Yes, as the engine overheat it dies. With some water flow it will run low for quite a long time, less at WOT. And then when you re-start (after it cools) it usually won't run as long because it is already warm. Next day, after full cooling, it seems OK for a while.

Amber deposits are usually gasoline - unusual in a hose not that old.
Thanks. I'll try to check cooling passages and flow. May also replace the hose just to eliminate that as a possibility.
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Old 08-05-2020, 17:13   #8
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

As you pointed out above, your fuel line is delaminating internally. Nothing to do but replace it with a good brand. I had the same mystery problem with a smaller Tohatsu and the new fuel line did the trick.
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Old 08-05-2020, 17:38   #9
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

I had a jet ski that would do that, but it was seizing. I drilled out the main jet to enrichen the mixture and it stopped. When it would seize sometimes the piston would melt over the ring and lose compression, take it apart free the ring, file out the ring groove, use muratic acid to eat the smeared piston on the cylinder wall and put back together.
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Old 08-05-2020, 17:59   #10
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

@Compass790: There's water coming out the telltale/pee hole, but I guess flow could still be restricted/insufficient. I understand that could cause hard starting, but would it cause a running engine to stumble and die?

Yes it definitely can cause it to stumble & die. It's what happened to our 2hp yamaha which has very small water galleries & it has no normal type telltale just a small opening on the leg that exhaust & cooling water comes out of. Fuel starvation can cause it as well as A64 pilot suggested but I wouldn't be drilling the jet yet if the problem has come about suddenly. First check cooling then check carby float level & for cleanliness. Also fuel filter & tank clean if applicable. I think its a good idea to install inline fuel filter on outboards & use a filterfunnel when filling.
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Old 08-05-2020, 18:52   #11
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

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Originally Posted by Waterford View Post
As you pointed out above, your fuel line is delaminating internally. Nothing to do but replace it with a good brand. I had the same mystery problem with a smaller Tohatsu and the new fuel line did the trick.

Will agree it could be the fuel line especially if you saw the inside liner collapsed at the end you cut off (its probably collapsed throughout and will cause fuel starvation). Common problem w/newer plastic hoses. Easy fix to change hose.
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Old 09-05-2020, 08:37   #12
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

I had a similar problem on a Tohatsu 8hp. Different engine, but the cause was a crappy membrane/fuel pump in the carb.
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Old 09-05-2020, 08:57   #13
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

What is WOT?
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[QUOTE=Jetx;3135216]I have a four year old 18hp Tohatsu 2-stroke.
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Old 09-05-2020, 09:54   #14
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

[QUOTE=anacapaisland42;3135707]What is WOT?
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Quote:
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I have a four year old 18hp Tohatsu 2-stroke.
Wide open throttle
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Old 09-05-2020, 11:05   #15
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Re: Tohatsu 2-stroke dies shortly after running at WOT, hard to restart

When ours did this it was due to a bit of dirt in the carb.
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