Engine suddenly stops and starts at full speed
 

I have a 19 year old Grady White 208 Adventure with a two stroke 200 HP Yamaha outboard engine. It has been well-maintained over the years, most recently receiving new plugs, fuel filter, etc. prior to the start of this season.

The engine idles well, and runs very well on smooth water, even at full throttle and 30-40 mph. However, when going over large wakes, or even more so in 1-2 foot waves, the engine will instantly stop and just as suddenly start up again after a second or so. It is exactly like a person suddenly pulls back the throttle and then instantly pushes it forward again. Very dangerous.

If I keep going at that speed, the boat will run for five seconds to one minute before it happens again.

With 1-2 foot waves, I can run at low speed (e.g., 5-10 mph). The problem is still there but happens much less frequently, probably only one tenth as frequently. So I can carefully crawl back to the dock when this happens .

Does anyone have any suggestions? Thanks!

You may have...
 

Dirty fuel, fuel tank, fuel lines. During turbulence, debris gets caught in your fuel supply tube going into the tank. When the turbulence stops, the debris dislodges and sinks to the bottom of the tank. Then the cycle begins again.

Water
 

Similar thought to what garysanfran said except check primary and secondary fuel water separator for water infiltration. Could be sucking in water during turbulence... easy check and cheap fix if that is the issue...

Dan

Exactly what I was thinking, dirty fuel is causing the issue.

The fuel filter should be easy to locate and easy to change. It is not a big job and does not require any special tools. You may want to try changing it now and again during the boating season if the problem arises again in a month or two.

sounds like a fuel issue with the tank or lines, for sure

Well if she idles fine and problem happens when water is rough doesn't seem like a fuel related situation. I would be taking the engine cover off and starting at the battery moving to the engine checking connections for cleanliness and being tight along with inline fuses for corrosion.

This also could be an electrical problem. However one thing at time.

Chasing a fuel delivery problem first is certainly worth the effort, in fact in a pinch you could try to run the engine off a portable gas tank with fresh gas to see if that cures it.

Most likely Fuel issue
 

I agree with Gary, although there could be problems beyond the fuel tank. I've seen similar symptoms from water in the gas. Fresh gas? Or did it sit at the marina underground tank all winter? Stabilizer added last fall? I'm thinking along these lines if you had no such problem last season, which means something new this spring. The debris has been accumulating for years and I think might have been noticeable before. I've also seen similar symptoms with a fuel pump that had issues that weren't noticeable until you try to put higher flow through the pump and it can't keep up. This may be less likely considering the association with rough water.
Please let us know what you find.

Easy way to check the fuel without running in rough water and having a different fuel source. If I read the problem correctly no issues on calm water at any throttle position including WOT it doesn't appear to be fuel. Issue comes into play in rough conditions. It states "engine just stops" fuel related problems will drive power down to a point she stalls and it won't just start right back up. JMHO

Engine suddenly stops
 

Make certain that the wires going to the key/starter are secure

I had a similar problem on a sailboat...
 

I kept in San Francisco.

After a very rough sail, then a DEAD CALM, my engine wouldn't start. An outgoing tide was taking me out of The Gate. I had to get a tow...Imagine not being able to set an operating sail in San Francisco Bay??? Embarrassing!

Anyway, brought it to SF Boat Works and they traced it to a screen over the tip of the suck tube in my fuel tank that was clogged. Sabre changed that design in later years. Any debris was then caught by my other fuel filters.

90% of fuel problems are electrical.

You have a loose wire, possibly a ground wire that is losing contact.

The big bumps make it go off suddenly and back on again.

To simulate this idle the engine in neutral.

Check every wire and harness and manipulate them in many directions.

It will be obvious when you find it.

I would start in at the kill switch.

Next, check the battery cables.

Then check the big bus connector to the engine.

If you are still looking st this point you may need to wear a head lamp and go spelunking!

Thanks for input
 

Thanks to all of you...lots of good ideas in here. I will post an update after I do some work on it.

I has a similar problem with my Sea Ray. Turns out it was the gas line from the tank to the engine. The line made a bend and at the clamp when the engine box got warm, the line would kink periodically. Mechanic was stumped unitl he and a helper took it out and ran it at WOT over some wakes while one of them had the engine hatch open and bingo, there it was. Simple fix was to re route the gas line to eliminate the problem with kinking.

Thanks for input
 

Thanks to everyone for your input. It may be a while before I get to address this problem, but I will give you an update on what I find.

Just remember that my sage advice has a five minute, five mile warranty. :D

Check this recent thread as well some seasoned boater/ forum advice here too on what could be a similar problem.


https://www.winnipesaukee.com/forums...ad.php?t=24498

I realize this is a year old, but with no conclusive response from the OP, I want to add my similar experience which may be exactly what they had happen. During rough boating, the 2 stroke oil tank would slosh around (if not fill) and a sensor would think the tank was empty. To keep the motor from a low-oil situation, the engine electronically cuts RPMs to save the motor from damage. Try topping off the direct injection oil tank and see if that solves the issue.