Fuel issue, maybe?

[johnsw]

OK, time to look into those crystal balls a bit. I had a transient issue on Sunday evening with my '04 Yamaha 150 carb 2-stroke. Ran fine for about 40 minutes when all of a sudden I lost power and RPM's. Crusing smooth at about 4500, I suddenly dropped down to a rough running 1400, or there abouts. My first thought was the engine went into failsafe mode, but had no alarms going off. I throttled down not letting it go to idle thinking if it stalls I might not get it started again. I didn't see it myself, but my wife said the engine smoked a bit right about the time this started happening. I throttled back up but it struggled to get much over 1200 rpm. Being only 15 minutes or so from the marina, figured we'd limp back as close as we can and radio for a tow if needed. As quickly as it happened, it ended. I felt the power come back, the engine smoothed out and I had full power again. Ran fine back to the marina at regular crusing speed and engine idle performance while docking seemed normal. Never stalled during the whole episode, which lasted I'd say no more than 2 minutes. At the dock, shut it down and restarted no problem on the first try. All seems 'normal'.

Not sure if it's connected but a few minutes before all this happened, we crossed several large wakes and things got shook up pretty good. I'm still running with the fuel from over the winter (splashed back on Memorial Day weekend with 3/4 tank on the guage). I always treat with Startron every fill up and add StaBil when winterizing. Now down to 1/2 tank so I plan on filling up next trip out (should take about 50 gal) and figure I'll replace the fuel filter after I fill up and dump the contents to see what it looks like (provided this doesn't happen again before I fill up). My mechanic has been pretty good about it and I'm 99% certain (since I didn't actually see him do it) he replaced it last fall when he winterized. But figured I'd do it myself just to be sure of what I've got.

Last ran the boat prior to this on Memorial Day weekend about 90 minutes, no issues.

These are new spark plugs, as I always install new every spring. I don't think I fouled a plug because I think I'd need to lose more than 1 cylinder to lose that much power, and then the engine came back so quickly once it recovered. But then, I've never had that happen that I'm aware of so I can't say that's a sure thing.

So with little else to go on, my plan is to fill up with fresh gas, add a bit more Startron than I usually would and replace the water seperator filter.

Looking for other opinions. Not sure if this is just one of those burp kind of things that happens once and never again, or the start of a bigger problem. Only time will tell. But I hate these intermittent things because you never really know if anything that's done actually fixes anything, and if there is even anything that really needs to be fixed.

John

 

[Hannibal]

Long shot here as there are numerous other reasons for your issue but mine acted exactly the same when water ended up getting under the engine cover. Oddly enough, a new transducer install on the stern end of the boat resulted in water being picked up from the river and directed up against the motor cover. After driving around, enough water got under the cover to disrupt normal function. It did the same thing you described.

After being forced to put put along (no performance), I guess enough water had drained out or burned off (smoke/steam) to allow normal function.

I didn't realize why it was happening until I saw a picture of my boat running around which showed a rooster tail originating from where the transducer was mounted.

Obviously your's isn't a transducer issue; however, is it possible the rough water could have led to things getting wet briefly?

 

[DaleH]

So with little else to go on, my plan is to fill up with fresh gas, add a bit more Startron than I usually would and replace the water seperator filter.

Add fresh gas, usual dose of Startron, and check your f/w separate if NEW this season. Do you have the one with the see-thru drainable bowl you can drain off if//when you see stuff accumulating? If not, IMHO you should. Go here to buy item #3516 if you need the SS head unit too, or just buy the replacment cartridge WITH drainable bowl to fit your existing head unit (made in 2 thread sizes).

I'm unashameably biased and opinionated (really :shock: ?) , but anyone runnng an OB-powered rig OFFSHORE without a drainable bowl is a fool ... a decision that could cost them their life, and the lives of others, in the wrong predicament! Like when coming in from offshore in heavy seas ... you THINK you can change a filter on the fly, that's why some use the closed-bowl version, but let me tell you ... you can't and may not be able to keep the boat into the seas and then change, while you're adrift. I've been on 2 boats brought home in serious seas, where the tank was sooooooo stirred up, the fuel was fuel of water and crap even though the boats always ran Racor f/w separators. To get both boats home, the crew alternated sitting at the filter, continuously draining crap off. If we had stopped the boat or if the motor(s) had died ... :shock: we would have been in grave trouble :shock: . You may even need reliable power just to get through some jetties and channels if/when there are heavy standing waves.

Think about it John ... hitting those boat wakes stirred up your tank ... thus I bet you either hit a slug of water from the fuel tank or dirt/crud from inside the tank momentarily stuck on the end of the fuel pickup tube, like finding navel or toe lint on your body ... ewwwhhhhh!

Check now or if it happens again .... remove the fuel sender and get a good look in your tank with a strong flashlight. If water, yuo'll see 'bubbles' of it down on the bttom of the tank. If no bubbles of water, then pull the fuel pickup.

See viewtopic.php?f=8&t=7175 and viewtopic.php?f=8&t=2326 for more info on pulling fuel pickups out.

 

[johnsw]

Thanks for the feedback.

From the way the engine was running, I'm still thinking it was a fuel problem. Most probably due to shaking up everything as well as I did.

Actually, I ordered a Racor with the see-thru bowl earlier this morning and having it sent priority so I'll have it next week when I go on vacation. It's been on my to-do list, but one of those things - out of sight, out of mind. And until now, no potential issues to 'inspire' me. My bigger concern is if this might be the dreaded phase separation that can happen with ethanol, even though I've always used ethanol treatment when it became available.

I'll also look at the possibility of water intrusion. As long as I've owned this boat, I've always had a few ounces of water drip from the rubber cowl seam when raising the motor to trailering position. Problem is, the few times I checked it out while the engine was still vertical, I never found water or dried water stains in the engine area. And it never seemed like enough water to be much of a problem. But, worth a second look.

John

 

[Megabyte]

I think you are correct that it was a fuel issue, but just in case... check the power cables going to your motor.
A loose connection can induce a similar problem.

When you change your filter, write the date on it with a Sharpie.
That way you will know if the mechanic changed it out or not.

Treat with fuel amendments and you should be good to go. :wink:

 

[johnsw]

Will do. I give the connections and wiring on the engine a quick once-over every spring when I'm 'de-winterizing', but it's a simple check so while I'm installing the new filter I'll give everything a second look just to be sure.

As for pulling the sender and inspecting the tank, that's proably a good thing to do every so often anyway. But I might hold off on that until fall unless I continue to have an issue. I think I remember reading on a few posts here that the screws holding the sender into the tank can sometimes be a PITA. Last thing I want while I'm in the water is to snap off one of the heads or strip it trying to do this, and making more work for myself while I'm in the water. Putting this on my fall 'to do' list, I can start a few weeks ahead of time soaking them with PB blaster as part of my prep work.

Thanks to all for the feedback.

John