twin yamaha 40's oil in fuel

C

CDory23

New member
I have twin yamaha 40s . 2003 carbuerated outboards. When I bought the boat I found a few different bottles of fuel stabilizers stored in the lazarette. A few weeks ago I finished off a bottle of yamalube fuel stabilizer- a little over the recommended dose but no big deal to me I have done that before I wanted to finish off the bottle. My next trip the engines bog down after about 15 minutes and are smoking. After some some thinking and investigating I came to the conclusion that the last owner must have put some sort of oil in the fuel stabilizer bottle. I took the bottle from the recycle bin and it was very viscuous and dark like an oil would be.

I took both tanks out and drained completely (took fuel to hazardous waste) then reinstalled and put new spark plugs in the outboards. The fuel was very discolored and looked like 2 stroke fuel. Over the last two trips there performance has improved but they aren't completely back to how they operated before and are still smoking. I've probably put around 10 hours on them although most of that has been idling because I've been doing drift fishing out in the SF BAY. I figured the fuel lines would have been cleared by now. Could this have damaged the engines? I"m wondering if I should now just dedicate a day on the lake to giving them full throttle until the rest burns out. I bought new fuel filters and new spark plugs but wanted to wait until the smoking stopped to install them.

Current symptoms are mostly light smoke and bad smell as well as rough when getting on plane and often dying when given full throttle.

Any advice appreciated.

I learned my lesson on never trusting a bottle that isn't sealed. This has been a real pain.
 
I'll offer advice based on running 2-strokes. Here are my comments, in no particular order.

That oil probably doesn't mix/dissolve in gasoline, so it's in there somewhere. Replace the fuel filter, it's probably is oil contaminated. You mentioned you drained the tanks, but did you flush them? Pump a couple of gallons through the fuel supply, right up to the carbs.

The carbs might be contaminated with oil, affecting the jets. Pull the float bowls, easy to say, and see if there's any oil there. Blow out the jets, especially the idle jet.

Pull the plugs and see if they're oil fouled. If oil is still coming through, it'll be on the plugs. Remember, in a 2 stroke, not all the oil is burned and it will show on the plugs. Put in the new plugs if the old ones show any oil fouling.

After you've done all that, take those motors out and run them at full bore for a while to remove any extra carbon the burned oil left in the combustion chambers.

Boris
 
Roger's advice would also be mine., for starters.

The fuel lines and filters should be clear by now.

What are the chances that the oil was not 4-stroke engine oil, but hypoid gear oil?

This could be a lot more viscous and perhaps harder to remove from the fuel system, since it might be somewhat (or a lot) less soluible in gasoline.

Just speculating.......

Joe. :smileo :thup
 
I also have a set of 2003 Yamaha 40's on my 22 cruiser.... and have had LOTS of problems with those darn carbs... they are notorious for clogging up and not running correctly.... In the 400 hour life of my motors I have torn them apart and rebuilt them 4 times.... finally just before the Delta trip I pulled them apart, all 6 carbs and rejetted them... made a huge jet change...of both my primary and secondary jets... the new jets cost $250 for the 12 pieces but it sure made a change in the motors... and hopefully they will not plug us so much.... they never did smoke but sure ran horribly... with the new jets I easily do 25 knots and my fuel mileage did not suffer.(4 mpg).. I think from the start those 40hp motors were jetted way too lean.... It takes about 4 or 5 hours to clean and rejet all 6 carbs but it really is worthwhile...

Your problem is not with the oil you added....that is long gone but it is krap in those tiny jets....I tried lots of carb cleaners....and all different types...still clogged up the jets.... nope...pull em...and re jet em..

Joel
SEA3PO
Camarillo and on my way to Chester for the summer
 
SeaWolf, I think you hit the nail on the head with it being hypoid gear oil. Not sure if this changes any actions that I will take but its probably going to lengthen the process of burning it all off. I"m going to pull a plug tomorrow and decide my plan of action from there. I"ve already replaced them once since the issue so don't see the point of fouling more up because if I see smoke I know the new plugs will be the same way after install.
 
I also have twin Yami 40's. They are 2004 versions I believe, and carbed. When I first got the boat, it had been sitting for several (maybe up to 10) months, and no way of knowing if there was Stabil in the fuel or not, however there was Stabil and Yamaha Ringfree with the boat and the previous owner was an experienced boater.

It had some trouble with running rough so went to the Yamaha mechanic where the carbs were pulled and cleaned, and then re-synced. Since then, (and running Stabil, Startron, and the Yami Ring Free regularly, I have had no - zero - nada issues with starting or running. I have spent considerable time running at slow cruise speeds and runn at WOT (about 5500RPM) for short periods, mostly cruise at about 3600 - 4200RPM.

In the spring, after sitting for a few months and having been fogged, they start up readily -- a few cranks, and they will smoke some, but after that is burned out, they run like a champ.

Joel, I am really surprised at your issues with the Yamis. I have over 800 hours on mine, twice what you have and it sounds like you have had yours apart more than running. Sorry, 'cause that would not be fun. You may be right that they were incorrectly jetted. Glad your past that.

Harvey
SleepyC :moon

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CDory23":3k9dw08p said:
SeaWolf, I think you hit the nail on the head with it being hypoid gear oil. Not sure if this changes any actions that I will take but its probably going to lengthen the process of burning it all off. I"m going to pull a plug tomorrow and decide my plan of action from there. I"ve already replaced them once since the issue so don't see the point of fouling more up because if I see smoke I know the new plugs will be the same way after install.
Click to expand...

How about pulling the plugs and cleaning them and replacing for another go around?

Harvey
SleepyC :moon
 
Joel, I agree the carbed Yami 40's are notorious for the carb issues. Jets are way too lean. If ran often (multiple times a week) they do great but if they sit for any time at all they do clog. The ethanol in the fuel doesn't help either. I have heard the re jetting solution and will contact you for details. I have been considering doing that.
When I bought the boat the port engine idled rough and had issues. The previous owner had a lot of reciepts of carb rebuilds on the engine which never seemed to fix the issue. I brought it into a trusted mechanic who recommended replacing the carb instead of rebuilding, it would have cost the same anyway, but he was very familiar with the Yami 40 issues said those carbs are very difficult to rebuild. Also told me to run the engines as much as possible. I run them up on the trailer at least every 2 weeks. The new carbs did fix the issues and they have been running ok until this issue. Very frustrating.

I need to fix this issue before my Catalina trip in two weeks. I hope to come up with a good plan of action tomorrow.
 
Are you using E10 or ethanol free gas? just curious

You could give it a "SeaFoam" treatment or equivalent fuel system cleaner. Seafoam smells like natpha to me.
Add Seafoam to portable gas tank and connect to OB bypassing the fuel tanks then run motor for 10 -20 min, turn off, and allow to sit overnight. The next day, run the boat as fast as possible and safely
 
Brent, I have considered seafoam and some people have miracle stories with the stuff. I do believe it works, but with this application I feel I would risk the seafoam doing its job but then potentially clogging the jets with everything it has cleaned from the system. If I were to do it I agree, the way to do it is run it through a small tank rather than adding it to main.
 
Unidentified something in a bottle of fuel stabilizer? Could be anything. I'll bet you will have to go for an end to end fuel system tank clean, hose clean, and carb tear down. I dump everything into old jugs from kerosene to oil to paint thinner to dirty paint brush cleaner and whatever else I have that needs to be hauled to the disposal.

This is a good lesson for all of us. Check that the pills in the bottle are what they say they are, and make sure that whatever goes into the fuel tank is what you think it is.

I put a full tank of farmer diesel in my 54 chevy once. And my wife accidentally took a near lethal dose of my daughter's anti psychotic pills thinking they were Excedrin.

Good luck and I hope it takes less effort that I've postulated.
 
Yes I agree. I was trying to not be wasteful and use instead of disposing. Never will do that again. Because of the smoke and the smell off the engines I'm certain it is a type of oil.

I"m looking into carb cleaning and replacing the jets just trying to figure out which jets to go with. Any input on this would be hepful
 
Jet hole size for a F40 Yamaha: From My Yamaha mechanic.
Main is size 95
Idle is size 38

Of Note. After the jets are removed, cleaned or changed the carbs will need to be synced and linked. (You probably already know this stuff).

Also of Note. The Jets may be sized according to the regional altitude of original sale. Boats purchased from Sea Level an moved up 3000 feet or more may have different size jets and will run differently than at 0 ft altitude. And the converse is also true.

Harvey
SleepyC :moon

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I think (for what that is worth) that Yamaha tried to make the engines really lean to make the three star emission standard.... in doing so they used the smallest jet that would make the motor run....when the jets get the least bit of clog in them they make the engine run horribly...too lean misfire.

I changed the main jet from a #86 to a #105 and the primary jet from a #38 to a #45... I found these fit a 2006 two cylinder Yamaha 25hp motor...that uses the same carburetor body. the part numbers are

Main Jet is 10-65W-14943 (#108)
low speed jut is 10-676-14948-05-00 (#45)

Rebuilding the 6 carbs is easy...just do one at a time, go slow, reuse all the old gaskets and blow out all the passages.... I used an untrasonic cleaner to clean the bodies but carb spray should work as well...

Joe l (Retired College Auto Shop Teacher, Oxnard College)
SEA3PO
 
Normally you would only change a jet size by 2 sizes...(one is not enough to see a difference) but I was limited to finding a jet that would work... and thus the huge difference in jet size....also my motors were really lean and almost would not run... really sensitive... hard starting too.

To locate jets, first look up the carb body to see what jets will work in that body.... and I wanted a large improvement so I went large in size... it does not appear to have changed my fuel mileage as I would have guessed , I just finished the Delta cruise and averaged 4 mpg and that was mostly running at 25 knots...(wide open) Sure starts easier and runs better, smoother and faster...

Joel
SEA3PO
 
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