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Hello to all...

I am experiencing a moderate rough idle and low rpm stall as of late with my 2007 90 TLR 2 stroke. It appears my primer bulb was not E10 compatible as is the fuel line when I replaced them some time back. I start the motor a few times each month when I can't get out with the boat. Last month I had no issues with idle, 2 weeks ago the issue presented. I do use fuel and Ethanol treatment with every tank fill along with Yamaha Ring free.

The O/B has just 97 hrs on it, I thought it might be the spark plugs so I replaced them (correct spark gap .039"). Started the O/B idle still rough, rpm would dip down to about 450-500 and stall. I inspected the fuel/water separator and viewed very small dark particles in clear site bowl. Engine mounted fuel filter also displayed same condition. I proceeded to drain the carb bowls for further inspection. Top and middle carbs drained clean but bottom carb had similar particles and drain fitting was coated with a greenish film. I assume the film is congealed 2 stroke oil and fuel?

I carefully sprayed into the bowl areas (externally without any disassembly) with carb cleaner in hopes of dislodging possible contaminents. I also sprayed and cleaned the throat and butterfly area of the carbs. All fuel filters have now been replaced along with proper primer bulb (new spark plugs too) and O/B still idles rough and stall condition remains the same.

It is apparent a carb rebuild is in order. I have contacted area boat service shops and the quotes vary from the mid $200's up to the $500's, "holy #%*@"!!! Are these quote accurate??? I am considering doing the rebuild myself with a good friend who just recently rebuilt his 2 stroke 90 carbs with great success. The rebuild carb kits are between $24 thru $31 on-line and a Yamaha service/repair manual is in order as well.

What has perplexed my friend and I are the "Pilot Screws" found on my Keihin carbs? They are capped with what appears to be a brass plug. My friend's Yamaha 90 is of a 1999 vintage and his Keihins have exposed pilot screws for adjustment. Our carbs appear very identical with that one exception. Are my 2007 carbs not designed to have the pilot screws adjusted or cleaned?

There were 2 other simple tests that I did with the motor. One was to check the actual (visible) ignition spark to the plug (Snap-On tester) which was adequate. The second was to pull off the spark plug boot (1 cylinder @ a time) with motor running and observe idle. Top and middle cylinders demonstrated increased hesitation when boot was pulled but bottom cylinder presented little change.

I apologize for the lengthy post, any and all assistance with my issue will be greatly appreciated. Also suggestions of Yamaha service/repair manual suppliers would be great.

My Keihin model number is:6H130 UL26 BCP
Yam. 90 TLR model number is: 6H 1 L 1033531 J
Date: 11/07

Thanks,
Angel M.

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If you replaced your primer bulb a few years back, it should be ethanol complaint. We in Michigan have had 10% Ethanol Blended gasoline for 20 years now..Actually we have had 15% for about the last 10 of those 20 years. The actual damage I have seen has been limited to non ethanol complaint fuel lines, rubber diaphrams and rubber seals degrading into mush and fiberglass tanks degrading from this fuel. But, that is from 10+ years of exposure to such fuels. I would not jump on the "Ethanol Ruined my Motor" Bandwagon just yet. Especially since you have a 2007 motor that would have fully ethanol complaint hoses, seals, etc on your carburetors.

While the fuel may not of hurt the actual components of your motor, even with a stabilizer it, the fuel could have gone bad. Ethanol blends do this at a much faster rate.

How old is the fuel?

After cleaning and emptying your fuel filters, have you hooked up a fresh, clean external tank with all new fuel and run the motor through it's paces and backed it down to see how your idle is?

And if you want a service manual, SELOC is the best one to buy.

On the cost of rebuilding the carbs, 300-500 is an expeted range. That said, I would not head that route until you have checked some other possibilities off the list first.

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I think Jeff hit it right on the head. First thing to do is try a clean and fresh external tank of fuel and run it through it's paces. I would use a double dose of Sea Foam conditioner in the fresh tank. You should also keep in mind that fuel stored in tanks probably have vent screws or caps that must be open when in use but absolutely must be closed when not in use. Water is the enemy with any fuel but more so with ethanol.

I don't care what anyone tells you. If there is water in your fuel or tank the only real way to get it out is to empty and clean the tank.

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Thank you gentlemen for the replies.

The fuel in the tank is a good few months old but I had added Sta-Bil ethanol treatment immediately upon purchase. I do retreat the fuel when a certain amount of time has gone by or the boat has sat for a spell along with Yamaha's Ring Free additive which also has E10 protection.

I have not detected water/moisture in fuel separator trap (I have the "clear site bowl" Racor) at anytime or when this issue began. What I had discovered where very small dark particles in the separator trap, engine mounted fuel filter and in the fuel bowl of the bottom carb when I removed the drain screw.

I had been noticing that my primer bulb with each engine start-up or boat outting had been getting harder to squeeze. In my fuel circuit the primer bulb is just before my fuel/water separator (it's visible in my "Fuel Tank" project album). The fuel that I drained from the tank feed line to primer bulb is/was very clean (no debris or water present) and I check numerous pour-out from the line.

I do not have a portable O/B gas tank to test with fresh fuel at the moment, will need to purchase one which seems prudent. The particles are what lead me to suspect the primer bulb must have degraded internally. My Dauntless had the oem Pate fiberglase tank with pre E10 fuel lines when I purchased it. My project album details what I revised and improved on. I know the fuel lines are E10 resistant (its stated on the hose/Sierra brand) but I think I got doped on the purchase of the primer bulb. I never thought to ask and it was in a generic package with no real description. My bad...it's about 3 years old.

The bottom cylinder is definitly not being feed fuel properly (on the low rpm) from my preliminary test, the Yamaha will rev up quite well. It's the idle which has been somewhat affected.

Regarding the shop manuals, Seloc was mentioned. I am considering the Yamaha Service manuals specific to my O/B serial number and build date. Any pro's and con's between Seloc and factory Yamaha that I should consider.

I am most likely going to go through the carbs myself with my friend who recently did his (1999 yam. 90 2 strk.) same Keihin carbs but with visible pilot screws. I have discovered the reason why my Keihins pilot screws are capped, EPA mandate to keep owners from enriching their air/fuel ratios. This situation also allow for a somewhat simple cleaning of the carb/bowl areas and components. I will not have a need to reset or rather adjust my "factory set" air mixture according to information I have gathered in the last few days.

Once again, my apologizes for the long winded post...

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Why don't you simply get another fuel primer bulb from Yamaha and replace the crappy one you have now. See if you still have particles. Your filter should be catching any particles you have now, just replace that too. Flush your lines to the filter with the clean fuel if that bulb was really disintegrating, then you should be fine. If you are not catching water in your filter separator, you don't have water contamination of your fuel.

Now, for something completely different- you may have gotten bad fuel. There is also the possibility that you have over added all those additives to the fuel to the point you have ruined it. You really need to run that motor on a different fuel tank with known pure good gasoline and see if that makes things go right. If you accidentally filled your tank with the E-15 gasoline blend, your Yamaha will not perform like it should and have symptoms that you describe. You HAVE to pay attention at the pump, Yamaha says NOT TO USE E-15! You can use E-10 with no prob.

TOO MUCH ADDITIVES IN YOUR FUEL WILL KILL IT. YOU CAN"T KEEP ADDING FUEL ADDITIVE JUST BECAUSE YOUR STORING THE BOAT AND NOT USING IT. IF YOU MIX THE ADDITIVE CORRECTLY AS PER INSTRUCTIONS ON THE CONTAINER WHEN YOU PUT FUEL IN YOUR BOAT AND THEN ADD MORE LATER BECAUSE YOU HAVE A FEAR OF ETHANOL, AND YOU USE BOTH STABIL AND YAMAHAS ADDITIVE AT THE SAME TIME, YOU ARE TRYING TO GET YOUR MOTOR TO BURN TOO MUCH ADDITIVE, YOU HAVE REDUCED THE OCTANE TO BELOW ACCEPTABLE LEVELS FOR YOUR ENGINE.

YOU SAID:
"The fuel in the tank is a good few months old but I had added Sta-Bil ethanol treatment immediately upon purchase. I do retreat the fuel when a certain amount of time has gone by or the boat has sat for a spell along with Yamaha's Ring Free additive which also has E10 protection."

STOP DOING THAT! PICK AN ADDITIVE AND USE IT, YOU ARE WAAAAY OVERDOING IT IN MY OPINION.

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Thanks silentpartner for the input. I suspect that the fuel pump took in the same particles as were present in the lower carb bowl. Flushing the fuel circuit as you suggest will accomplish little at this juncture. The contamination is real.

I should have been a bit more clear when I said "retreat the fuel". I just don't randomly add ethanol treatment when it suits me.

I don't fill my fuel tank at the pump as most would, I refitted my Dauntless with a Moeller above deck plastic 18 gallon unit. I typically from a day of boating will not run the tank dry, it will be back on the trailer with anywhere from 5 to 8 gallons left. I have 2 dedicated 6 gallon plastic "Jerry-cans" for my boat. I treat each container independently for ethanol when I fill them, so when I re-fill my boats actual fuel tank from the containers the fuel going in has been pre-treated.

The fuel stations in my area of Miami, FL are not as of yet dispensing E15 (I do check the pump info) and hopefully in no time soon. The fuel was not bad or tainted as suggested, the same fuel fill was used in our daily drivers with no issues.

I did mention in my previous 2 posts that the primer bulb and all fuel filters were immediately replaced with E10 compliant units if in case that detail was missed.

The fuel treatment that I am using such as Sta-Bils Marine Formula/Ethanol treatment and the Yamaha Ring Free fuel treatment have excellent compatibility with each other. In fact they enhance each other because their applications for the outboard are slightly unique onto themselves. I only use the Yamaha Ring Free with every other complete fuel fill.

I have used on a few occasions since redoing my boats entire fuel circuit some time back the "For Recreational Use Only" 89 Octane Ethanol free fuel, unfortunately gas stations in my area that offer it are very scarce. I have purchased it when I'm down in the Fl. Keyes but thats not very often or at least with the boat in tow.

As I mentioned previously the primer bulb over a period of time and use had become extremely stiff, to the point that my hand would cramp-up from trying to compress it. I would have to pump it anywhere from 10 to 15 times to initiate fuel flow. The new primer bulb is packaged by Marpac. It is blue in color due to the material being able to remain pliable in cold weather and is quite easy on the hands when compressing.

It has a new twin bore check valve design that I will attest moves an incredible amount of fuel with minimal effort. From changing the filters and previous primer bulb the fuel line had obviously lost it prime, after reassembly it took no more than 6 or 7 compression's and my fuel/water separator was completely filled and fuel was heading into the outboard. "INCREDIBLE"!!!

The previous primer bulb is roughly 3 and a bit years old never exposed to direct sun light due to my set-up, I still have it and as I am writing this post I took it in hand and tried to squeeze it and it will not give. It's rock hard, no visible markings to prove it a Yamaha product. I will be eventually cutting it open for an inspection of it's interior.

I am fairly certain that the fuel is not the problem, the particles I found could only have been generated by the previous primer bulb's material break down. I have ordered OEM carb rebuild kits, new fuel pump assembly, Factory Yamaha service manuals and appropriate cleaning solutions. I will have excellent help on hand for the carb rebuild as well.

I will post on end results... thanks to all who posted.

Angel M.

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Update...

In my original post I had asked if anyone on the forum new why the air mixture "pilot screws" in my yamaha 90 2007 model Keihin carbs are blocked off from adjustment.

I came across a post stating that the EPA had mandated this feature sometime in either 2004 or 2005 to prevent tampering of the 2 stroke outboard's air/fuel mixture ratios.

Does this sound plausible???

Fortunately in my case it will be one less component to disassemble and tune during/after the rebuild. The pilot screws are factory set or tuned for proper air ratio. A Yamaha master tech posted on a different forum that the only time he would remove these pilot screw plugs (because they must be drilled out) is if the motor had been submerged or more serious carb contamination was present.

Just an F.Y.I. to all...

Angel M.