Engine Loses Power When Water Rough
 

We just started having an issue with our Yamaha 150hp 2-stroke on Saturday. The engine will lose power (not stall) abruptly when we hit a few decent sized waves. Once we're over the waves, the engine runs fine again. It occurs only for a second or so and seems to happen at mid-to-high rpm. If putt-ing along we haven't had the issue.

Definitely feels like the engine must not be getting gas. I'd suspect a float issue, but the engine is fuel-injected. Thoughts?

Loose electrical connection or corroded connector. I would start with the battery connections and then check all the electrical connectors.

Def sounds electrical to me... but just in case I would put on a new fuel filter...

Woodsy

I'm going with electrical on this one. It could be as simple as a loose spark plug boot. That could cause sudden power loss but the other cylinders would keep it running.

Does the engine cut out or rev up?

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Engine Slows Down
 

The engine doesn't 'cut out' per se, it feels more like somebody just throttled way back suddenly and then pushed the throttle forward again equally quickly.

We did have some work done on our nav & anchor lights recently (new circuit breaker installed behind console). Could be that the technician was troubleshooting a loose wire at the battery and didn't reconnect it well?

Dropping spark in a cylinder and it suddenly returning could feel like that. Is it fuel injected? Maybe a loose wire somewhere in the EFI system is the culprit.

Possibly Prop?
 

do not know if my "similar problem" is relevant to your outboard, but my alpa I
outdrive at high speed, was losing power and engine rpms went high. problem was that I have a through hub exhaust propeller ( i believe that was the term used) and some type of pressed ring diverter at the "wake" side of prop was missing and/or had come off due to corrosion. this is only an issue when boat is a high speed, which is seldom. otherwise the prop is still usable

My thought as well. Make sure everything is clean and tight.

Could be
 

At the risk of being redundant, its most likely electrical. That said, I would also check to see if something is floating/resting in your gas tank. The rough water may move it around in there and put it right over the hole to the gas line momentarily.

Or even some water in the tank, that is picked up when the tank is sloshing, or your on plane and the angle of the tank is enough to cause the water to be picked up.

I have a problem too
 

Ok , I'm having a similar problem. Last season the engine started to stall when tubing, making turns. Goes away for the winter and ask the shop to look into this... No problem found.

Now I get going, hit waves, start turning and it stalls. Go for a calm evening ride no problem. Then it gets worse , stalling at any speed going straight in calm water or after 5 minutes idling at dock.

Different mechanic looks at it, finds I got a lot of water in the fuel. Drain the tank, bring it back .... The same problem. Then trouble shooting and figure it is the up coil. Find one in mass... $295. Goes in today... Take it for a ride, get it up to about 2800 rpm and it stalls, restarts right away every time. Can't go more then 500 feet and it stalls. I'm at wits end , we basically have been down since July 8.......

Any thoughts.. 1995 cobra 5.0 in a four wins. It's like my summer is over with.

I once had an issue similar and found that my fuel tank wasn't venting properly and it was like trying to suck out of a bottle. When stopped even momentarily the pressure equalized and all seemed well. This is an easy one to scratch off the list by opening your fuel cap and see if it goes away.

done that, ran it for about 1000 feet and it stalled.

It is just strange that it starts right up... give it a minute and we are off until the next episode.

my mechanic called me back this morning, we is baffled ... and this guy is highly recommended. he has worked on all my "toys"

When you drained the tank did you also clean/replace the fuel filters/water separator? Sounds like it's not getting gas.

Are you able to rev the engine to 2800RPM without engaging the drive?

Edit: this might be a good read. Problem was the fuel pump.
http://www.winnipesaukee.com/forums/...ead.php?t=6505

This sounds like a problem we had a while back before ethanol. Boat slowed down and would barely idle after crossing rough water. We would wait a while and it would restart and run normally. After all the easy fixes like tune up, coil, intake gaskets, carborator gasket, I pulled the gas tank and dumped it out into buckets. Besides some water there was a surprising amount of debris. It was sucked into the pickup tube screen blocking flow.

This was a 1980 boat before ethanol problems caused all sorts of fuel problems but it is worth checking.

Sure sounds fuel related as in not getting enough. CL might be on to something.

Borrow an external 5 gallon tank and hook it up to your engine. Then run and see what happens. People still use these tanks and a marina should allow you to borrow one. That way you bypass your entire fuel system.

Vent?
 

If this were my little outboard, I'd suspect the (remote) tank isn't venting properly.

I had same issues......

Tunred out to be bad gas that had sat in tank for over a year without being treated.

Not me who neglected... but prior owner when I purchased the boat.

Had gas tank pumped out, filled with fresh gas, treated with Startron, changed fuel filter, and issues disappeared ! :)

Good luck !