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Yanmar stalling issue

Sep 19, 2019
5
Hunter 33 Niagara Region
Hi there,

Wondering if anyone has had similar issues with their Yanmar 3YM30 stalling out? Purchased our 2004 Hunter 33 last year, and no engine issues. Boat had about half a tank of fuel when purchased. We immediately topped off tank, then again at end of season and added conditioner for winterization.

This year, seems after each day out, engine seems to stall. The rpm's drop and it either idles, or stalls. Have changed fuel filters, and fuel pump (when using the primer on the pump, no fuel was coming through filter - changed the pump and immediately solved issue). Same day after changing pump, ran the engine in gear at the dock for 20-30min, no issues. Went out for a sail, upon returning to the marina, started engine and began cruising at 2800rpm, then felt engine slowly start to randomly lose rpms. If i put it in neutral and throttle up, rpms would climb, but go down again. Didnt stall this time, but definitely seemed like a fuel supply issue.

So, seems like engine runs fine until either we hit open water and fuel gets shaken up, or after engine heats up, somehow that's affecting performance.

Any feedback would be greatly appreciated!

Thanks,
Mike
 
Feb 26, 2004
21,212
Catalina 34 224 Maple Bay, BC, Canada
Something to consider:

 
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May 27, 2004
1,499
Hunter 30_74-83 Ponce Inlet FL
Junk in the tank?
The treatment kills the bugs, but it doesn't get RID of the dead algae.
Air in the fuel line?
Air leaking in causes loss of power.
The "fading" you describe could be caused by either situation.
 
Jan 4, 2006
3,023
Hunter 310 West Vancouver, B.C.
You're on the right track starting simple. With the work you've done on the fuel supply, pretty safe to say that's working, even if only temporarily. Maybe large deposits of crud in the tank but the filters can handle them in the short term. @Stu Jackson 's comment is definitely worth looking at if you have the same filter.

Next easiest target would be the mixing elbow:

Dirty Sectioned Mixing Elbow.jpg


Notice I said easiest (not cheapest).

STS Invoice.JPG

This is a likely culprit if the elbow hasn't been checked since 2004. You MAY be able to knock out some of the larger deposits of carbon but a small charge of C-4 explosive is often required. Usually requires replacement.

Check out the archives to see what's recently been said about Yanmar mixing elbows. I installed a 316 SS mixing elbow (same casting)two years ago in the hopes of eliminating the corrosion products as well as the sticking carbon. Recently another member, @Ken13559 commented that he may be seeing pinhole corrosion on his SS mixing elbow so it may be back to the drawing board. I've still got an inspection to do after two years in service.

Exhaust Elbow SS.JPG
 
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Jan 22, 2008
667
Hunter 340 Baytown TX
By no means am I a diesel mechanic by the stretch of anyone's imagination. I used to fight my stalling 3GM30F constantly. I replaced the mixing elbow, changed filters constantly, tried turning up the idle. Always stalling when I was trying to dock in a crosswind or something.
I changed the Hunter factory filter set up to dual filters with clear bowls and drains, with an electric fuel pump. I can valve in the new filter pretty quick. I still stall every once in a while, and when it does, the clear bowl on the online filter is always full of water. I drain the water, and I'm fine until the next time I forget to check it before I leave. Usually only problems with water when I've recently added fuel. And every now and then I'll open the return line, turn on the pump and polish the fuel. That always puts a little water in the bowl.
The original Hunter setup with out a water drain is a POS in my opinion. No way to know when there's water in it or drain that water. I'm sure a mechanic will tell me what really happens when water bypasses the filter, but it has to be happening on those single filter set ups with no drains that only get checked or changed once every two years. And if you do have water problems in the fuel, it could be the cause of the stalling.
I'm sure I've just jinxed myself to future stalling problems.
 
Oct 22, 2014
12,831
CAL 35 Cruiser Portland OR, moored EVERETT WA
In my experience stalling is a exhaust issue.

Fuel starvation usually is exhibited by the engine surging, increased RPM. If minimal filter block this will happen then disappear and the engine will run fine for a period. Then repeat. If severe the engine will race up and then stop. Then you know you drained the fuel from the lines. Better change the dirty filter, bleed the fuel lines and try a restart.

I hate the bleeding of fuel lines. Takes me 45 minutes. Ugh. First sign of a surge I try to stop. Engine and do a filter change.
 
Jan 7, 2011
1,997
Oday 322 East Chicago, IN
Tank vent plugged?

My JD tractor would run for about 30 minutes, then die. I changed filters on it, and she ran fine...for another 30 minutes or, then die. Turns out the tank vent was plugged, and it took about 30 minutes for the vacuum on the tank To overcome the fuel pump...and she would die.

she ran fine after the filter change, because that let air back into the tank...

Greg
 
May 24, 2004
6,435
CC 30 South Florida
The old adage, 85% of engine problems are fuel related. What you are describing sounds like clogged fuel filters. Go back to the water separator and drain any water and keep draining until you get pure diesel fuel. If you found an inordinate amount of water in the fuel then replace the filter once again. Then check the seal on the fuel filler cap as rain water could be entering the tank. If no water and good level of fuel is found then move on to a possible air leak. You do not indicate if after the engine dies if you can get a clean restart. This info could help diagnose better. Fuel tanks will usually accumulate dead bacteria and other sediments in the bottom and these sediments will get stirred up with boat motion in high waves. These stirred up sediments can come together into globs that can block the screen in the tank's fuel pick up tube. The result will be fuel starvation to the Primary/Water separator Filter which is fed by gravity. That blockage can be intermittent as that glob can settle back into the bottom of the tank or move away from the pick up tube. If you find any indications of excessive water or blockage arising from the tank I would suggest you get your fuel polished. I will not clean your tank but will remove any water and most any large globs of bacterial decay. To test if a dirty tank is the problem you may remove the fuel line from the water separator and connect an outboard portable fuel tank filled with diesel fuel to see if the problem persists. Moving on inspect the fuel lines and filters for any fuel leaks. Where fuel will leak out when the engine is running, the air can leak in when the engine stops. Usually air leaks will not allow a clean restart until the air is bleeded out of the lines. The bleeding process is critical and needs to be thoroughly done as air can get trapped and create intermittent flow problems. Fuel and air leaks can usually be found in line connectors and fouled bleed screws that fail to hold a tight seal. Lastly check the air intake tube for any obstructions. Yanmar's sponge air filters are disintegrating and being inhaled by the engine and that is OK but make sure there are no other obstructions that should not be there. Now that we are checking obstructions make sure the vent hose to the fuel tank is clear and no critter has set residence during the winter blocking necessary air and pressure flow. If none of what I have suggested works then we may have to look beyond the 85% of fuel related issues.
 
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NYSail

.
Jan 6, 2006
2,546
Beneteau 423 Mt. Sinai, NY
Second the tank vent..... spiders and mud dobbers love those places. Next I would check mixing elbow.

Good Luck
 
Sep 19, 2019
5
Hunter 33 Niagara Region
Thanks for all the feedback, great insights! I replaced the fuel pump, and immediately had success with engine. Ran fine for 30min at the dock. Went out for a sail in rough waters. When I ran the engine to return, ran fine, but would sputter a little intermittently. Removed filters (which were changed week before), it appears there is water in the fuel, and likely sediment as well. No option to polish fuel until on the hard.

Any recommendations for fuel additive to add for best results of dispersing water in the tank?
 
Jul 5, 2011
505
Oday 28 Madison, CT
When she stalls do you hear the fuel pump still running? Loose or corroded connections will do that, loose happened to me once.
 
Oct 22, 2014
12,831
CAL 35 Cruiser Portland OR, moored EVERETT WA
Check out this article from Practical Sailor.

I have been using a combination of StarBrite and BioborJF in my tanks. It has helped me fight the combination of Culture A and B to get fuel that is clean. Not perfect but better I my tanks. I don't go to sea without back up filters.

The polishing of fuel is essentially running the fuel repeatedly through a filter. The cleaning of the tank is emptying the tank and getting inside to remove the sludge and goo. I have been able (through the magic of chemistry) to minimize the sludge and goo getting a reliable fuel system that powers the boat over 10 hour motor cruise when the wind is not blowing.

Not sure about your boat , but I have 2 filters. A primary Racor 500, and a secondary smaller filter on the engine. Both need to be on your maintenance schedule if you have them.
 
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Feb 26, 2004
21,212
Catalina 34 224 Maple Bay, BC, Canada
Any recommendations for fuel additive to add for best results of dispersing water in the tank?
WaterZorb is something I used years ago, don't know if they still sell it. Concept was to make the water droplets so small they'd get thru to the injectors and go boom with the fuel.
Since you say you have water in your tank, why not just get a hose DEEP-est inside your tank and get it all out. Chemicals won't help if you have a lot.
Then change your deck fill cap to something that won't leak, or at least check its O ring.
Good luck.
 
Jan 5, 2018
158
Hunter H34 0828 New Orleans
Similar engine, similar problem. Turned out to be air getting in my fuel line at the petcock on the fuel tank. If u have a racor or something similar and see a bubble (any bubble) coming through the bottom, then your getting air in your line. This air will eventually displace the fuel in the racor, thus causing the lines downstream to run dry, thus causing the engine to stall.

this entire process (running out of fuel) took about 30-minutes after bleeding the lines...

best of luck!! Shannon
 
Oct 22, 2014
12,831
CAL 35 Cruiser Portland OR, moored EVERETT WA
If u have a racor or something similar and see a bubble (any bubble) coming through the bottom, then your getting air in your line.
Interesting. Where would the air be coming from, the lines from the tank to the Racor or the Racor to the engine.

As suction is on the engine side, I would not expect air entering on that side. What say you?
 
Jan 5, 2018
158
Hunter H34 0828 New Orleans
I narrowed down the leak to the fitting itself. Because of the ‘vacuum’ created to lift the fuel, there was never any fuel spilled around the fitting. As soon as that fitting was out of the loop, problem of ‘bubbles in the Racor’ stopped.
 
Jan 12, 2016
247
Hunter 410 Ladysmith, BC
Starton Tank Cleaner

The above product would be worth using if it's really bad. I would also consider using an oil extractor and sucking out as much water and crud off the bottom of the tank first and dispose it somewhere that takes waste fuels. Then treat the tank with the above product and give it time to work.

The best solution is draining the tank completely, and getting the bottom and walls inside completely cleaned out of all residue. How far you go with the cleaning is really dependent on the severity of the crud in there. Hopefully if you caught this issue early enough, the Startron Product above may be able to tackle it.

The only issue with Startron products versus something like Howes is that it emulsifies the water rather than demulsifying it. This means with Startron it can eventually let the water molecules get small enough to pass through to the injectors and burn away, rather than get collected at the racor. I prefer using a product like Howes for regular tank maintenance as it demulsifies the water so it ends up in your water separator, but if I had to deal with what your facing I'd likely try and suck as much of the water out of the tank first as described above, then use the starton tank cleaner as a one time treatment. Just be sure to read the directions of use on the bottle carefully.
 
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