Engine stops suddenly in rough seas and starts again

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#1
I have a year 2000 208 Adventure with a 200 HP two stroke Yamaha. It runs great on smooth seas, from idle to full throttle. But when seas are 1-2 feet, or sometimes over big wakes, the engine often stops suddenly and just as suddenly starts up again. It is as if someone instantly pulled the throttle all the way back and instantly again pushed it fully forward. This happens most frequently when I am going at half to full speed. For example, stop/start, runs for a short time (five seconds to one minute) then stop/start again. If I go at very low speed (5-10mph) I can go for five to ten minutes before it happens again.

The marina changed my plugs and fuel filter prior to this season.

Does anyone have any idea what's going on?

Thanks!
 

loafer-roatan

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#2
I had a wiring issue once and every time I turned one way the engine would sputter. It was chaffed where the wiring went into the hull on the transom. Maybe check this?
 

SmokyMtnGrady

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#4
Yep, either a loose ground or other wire or a fuel supply issue. I know this doesn't help much. Pick the low hanging fruit first though. It almost seems you need to start at your fuel tank first if you check the fuel. The more I think about it, pull the cowl and check all the electrical and then check the electrical in the stern, battery, ground and such. Though once running , outboards don't need the battery , so check your wires for connection and corrosion.

Once that is done , check you fuel tank. It sounds like maybe debris is getting stuck on the supply line to the motor or something in there is loose?
 

seasick

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#5
Are you saying that the motor stalls but starts running again without you doing anything?
Yes an intermittent electrical issue could be the problem but I have seen several cases where a clogged VST screen causes the motor to surge. I can't say that the motor actually stopped completely though.
 
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Are you saying that the motor stalls but starts running again without you doing anything?
Yes an intermittent electrical issue could be the problem but I have seen several cases where a clogged VST screen causes the motor to surge. I can't say that the motor actually stopped completely though.
I don't think it stops completely. Think of a guy pulling the throttle all the way back quickly and then just as quickly pushing to to full throttle. I'm not sure but the engine may not actually stop in between. There is no human intervention between the stop and the start. (I have a stupid question: What is a VST screen?) Thanks!
 

DennisG01

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#7
If it's happening that quickly, I think the issue is right there at the engine. There's enough fuel in the VST tank where an obstruction downstream somewhere shouldn't have an effect that quickly.

Inside your VST tank is the high pressure tank. Attached to the pump is the VST filter. It would be an excellent idea to open up the VST tank and check things out... debris, etc. You could at least drain some fuel out and see what it looks like.

Running with a fuel gauge attached (hood off is fine) would be a good idea.

Also look at the engine-mounted fuel/water separator. The red ring should be at the bottom and the canister should be about 1/2-ish filled. Observe that while you run with the hood off, as well.

Someone feel free to add to this, but I think if you do the above you'll be able to narrow down the area of concern pretty quickly. Post your results of these things.
 
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I don't think it stops completely. Think of a guy pulling the throttle all the way back quickly and then just as quickly pushing to to full throttle. I'm not sure but the engine may not actually stop in between. There is no human intervention between the stop and the start. (I have a stupid question: What is a VST screen?) Thanks!
I just read a post somewhere in which a guy had a similar problem and it was water in the VST. The water would get sucked up when he went over waves at high rpm. I guess this is another thing to look for.
 

DennisG01

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#9
I just read a post somewhere in which a guy had a similar problem and it was water in the VST. The water would get sucked up when he went over waves at high rpm. I guess this is another thing to look for.
And... draining the VST (or checking fuel as mentioned above) as I mentioned will show you that.
 

Sdfish

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#10
I had the same issue on my 1999 Saltwater series 150 Yamaha 2 stroke. I thought it was the VST as well. Unfortunately, mine ended up being a dead cylinder, the one on the bottom left side of the block. Run a compression check before replacing the filters just to be sure. Hopefully you are good and my issue was a fluke. Let us know what you find out.
 

Ozz043

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#11
Ok well I’ve only just solved a very similar fault
It turned out to be the blue ground wire from the high pressure fuel pump in the vst.....
I was lucky enough to have it stop then not start in the marina when fault diagnosing...

See thread, sorry I don’t know how to post the link

99’ 250hp OX66 died but started again ?