Yamaha 90 stalling - 89 vs 87 Octane

[jbdba01]

OK - so let me come clean here...I've been hanging out on this forum for quite some time. Looked at several boats, even called on buying a trailer for one, but I'm not a C-Dory guy [yet].

With that in mind I have a quasi general outboard engine question regarding gasoline.

I have a 2003 2 stroke 90 Yamaha. Recently I started using Ethanol-free gas; the engine seemed to really run smoother with it. Idling was much smoother, running was much smoother...basically it felt pretty good. I was on the 2nd or 3rd third fill up which should have flushed all the older gas out.

This weekend for the first time in her history the engine refused to cold start after we have been out half the day and having moved around several times - in other words no issues. It almost sounded like she wasn't firing. After a couple more tries she started up but only by engaging the choke - which she never has needed after the initial start.

We motored around, and decided to cut it and start again. No issues. We chalked it up to air in the line. After a while I fired her up successfully and started going in. I normally cruise in at 4000 rpms and all was fine until she sputtered out and stalled. Hmmm...not good. After a couple tries she started up again.

We cruised in without much issues and my routine is to go wide open throttle the last 1/4 mile. At 5000 rpms life was fine and my buddy commented on "Sounds fine." And of course that cursed the effort. She started sputtering...I backed off to 4000 rpms and all was fine again and we limped in.

I had about 1/2 a tank of gas. Which I've run on before.

Some notes on the engine - I'm pretty darn good about maintenance. New plugs, new lower until oil, fuel water separator is 6 months old, I changed the micron inline fuel filter a while ago, and a quick visual showed it look OK clean.

So the $100K question is...could 89 octane gas ethanol free cause the stalling? I read up on running to lean might, but I figured I would ask here.

Thanks in advance.

[Will-C]

For me I think the regular gas will do fine. A 2003 engine maybe it's time to have the carburetors serviced you know like clean and adjusted. I would think about changing fuel filter/s first. It almost seems like the engine might be starving for fuel at least at lower rpms. Maybe the primer bulb needs to be replaced as it could be 13 years old and they do deteriorate over time. I would check your fuel hoses and see if they were rated for e ethanol gas so see if the previous use of ethanol caused then to also deteriorate over time. If you don't already I would also use a fuel additive like Marine Stabil or Startron and Yamaha Ring Free. Do one thing at a time and see if you see an improvement. I'm sure others will chime in.
D.D.

[BrentB]

I agree with Will-C

Some type of fuel restriction

Fuel primer bulb flow direction (arrows) needs to be vertical or pointed to the sky due to check valves to operated correctly

Check the fuel tank vent on the hull. Maybe clogged.

Does the external Racor fuel filter have a clear bowl ? Any water?

Does the fuel tank have anti siphon valve or ASV? They can clog

Tighten hose connections. Was the filter recently replaced? Maybe it is sucking in air

Does it occur with tanks full or low? If low it might be the tank pick up line

I dont think it is the gas and if the easy stuff does not work then start at the tank and follow gas flow to the cylinders.

Check the fuel pumps. Turn off motor then turn on but not start. Can youy hear the fuel pumps energize or turn on. Easier with a helper and cowling off

[Wefings]

Additionally to previous suggestions ,check the fuel pickups in the tanks as well. The tanks warp over time and we have seen them go to the bottom of the tank and get clogged or press against the bottom.Should be cut diagonally . Also inspect inside of fuel lines to rule out liner failure .
Marc

[tsturm]

[jbdba01]

All good suggestions, and comments.

Fuel was 1/2 tank. I've run it lower.

Tank is built in. How can I tell if anti siphon valve or ASV?

Pretty sure vent is OK. I'll doublecheck.

Fuel separator was replaced 6 months ago. No sputtering and has run fine since replacement many times. I've never looked at primer ball; it pretty much sits in the same position every time.

Re. "In the olden days the 2 strokes had a vacuum operated
diaphragm fuel pump or 2, bolted to the side of the block. " I'll pick up a fuel pump too. Pretty cheap at $50. It's an old school engine.

Let's see where this goes...was planning a night trip, but that sounds like a not so good idea now.

Oh yeah...I think I'll pick up a subscription for Sea Tow too.

Re. "different octane ratings have nothing to do with rich / lean mixture" - one more thing for the book of knowledge.

[BrentB]

Typically the ASV located on top on tank connected to fitting usually an elbow and the fuel pickup tube inside the tank is connected

see

http://www.thehulltruth.com/boating-forum/531187-fuel-tank-venting.html#b

[South of Heaven]

OP: Since you're diligent with your maintenance and have done all the normal things then it's time to "kick it into overdrive"....Lol

I just went through what you're going through right now. I have a 2003 Yamy, F80, 4 stroke carb'd motor. I did EVERY single maintenance mod known to man...NOTHING helped until I had the carbs cleaned and synced. Now it's like a new motor! Starts and runs like a champ ( at any temp or RPM).

You're gonna have to spend about $1000 bucks (give or take); unless you can know a guy or can clean the carbs yourself. I ended up spending $1100 but it's the best $1100 I ever spent in my life......

[jbdba01]

We have several good mechanics over here...may be the better part of valor just to have them give it a look over.

Stay tuned...

[BrentB]

I think tsturm has a good idea to check the fuel pumps. They can be easily be rebuilt . check with local shop , Andy at SIM or Boats.net for diagram or factory shop manual

[thataway]

There has to be a method to diagnose fuel problems: This is basically the sequence I follow,

First I check the primer bulb. It is full, and hard when you squeeze it? If so, you are getting fuel to the bulb, and thus into the start of the engine fuel system. If the bulb is pushed in, or you cannot get any fuel flow, then there is either: obstruction to air vent in the tank, an obstruction to the fuel pickup, in the line, anti siphon valve bad, or in the filter (assume it is a Racor or Sierra--If Racor, and a clear bowl, check the bottom of the bowl, and drain the fuel, to see if any water.

If the bulb seems to pump fuel well (if any question, pull the fuel line where it goes into the motor, and pump some gas thru that line with the primer bulb). --and the engine sputters, then pump the valve and see if it gives more fuel to run, this may indicate that the fuel pump is bad. Also check all filters inside the of the engine cowl. No matter if old or new--also look for a water separator--many outboards have a specific clear bowl for water separation. Also as part of the diagnostic I will replace the Racor, and check all of the fittings--both for leakage, and obstruction. One time I had an intermittent fuel obstruction, due to teflon tape which would periodically cause obstruction of fuel flow out of the Racor. Also check all "O" rings on the filters.

If you are still not finding the source, then hook up a fuel tank, with its own primer bulb to the input of the outboard. This completely removed the boats tank, lines, filters and bulb--which will then allow you to rule these out as the culprit.

Also you want to check the fuel flow just before it goes into the injector pump, or the carbs. When you squeeze the bulb, it should push fuel thru to that point.

If the fuel is good, no air bubbles, and clean, then the problem is most likely due to carburetor or injector pump problems.

Some carbs you can pump carburetor cleaner into the bowl, and up into the passages with a "spray can" of cleaner. Let it sit there overnight, and then try and blow out the passages, with an air compressor--if there is enough room to get tubing into the input.

[jbdba01]

[jbdba01]

So after sleeping on it a night and checking out the photos again that sediment/blacks specs has to go somewhere. It doesn't appear to be making it to the engine's fuel filter.

So I'm wondering if there's a filter/screen in the ball pump itself. Or perhaps even on the water fuel separator going to the ball.

That said, those fuel lines need replacing.

More work required...

[BrentB]

Unfortunately you check the simple items and that does not solve the puzzle, you follow the gas from tank to the cylinders.

I have seen pics of the fuel diaphragms develop pin point holes and small tears and easy to work on

I would upgrade the hoses, primer bulb and filters just m2cw.


We had a fuel flow management sender go bad and restrict fuel flow. I dont know if you have one

Good Luck

[ZoeB]

Not sure if you have replaced the fuel engine clip. I have had one of those go on me and the problem was intermittent. Have also replaced my primer bulb 2x in the past 3 years.

My friends Aquasport had an intermittent problem with the pickups getting clogged.

I would definitely check it with a portable fuel tank with its own primer bulb and fuel clip.