Yamaha Outboard

[JJinSC]

Hey, This is off topic, so I think I have this in the right place. Is anyone familiar with Yamaha outboards? Besides my SeaDoo, I also have a Key West boat with a 2001-90HP 2-stroke Yamaha on it. Last year, if I ran WOT for a couple of minutes, it started acting like it was starving for fuel. If I cut back on the throttle it would clear and run fine. Last week it started doing this at 4200 rpms and has actually done it on a couple of take offs. Again, cutting back on the throttle and it clears up. I have replaced the water separator filter and I keep fuel/ethanol treatment in the system. Any ideas??

 

[Dr Honda]

It suffers from the same issues as our seadoo's do. The TEMPO or other USCG approved fuel hoses suck. Replace the hoses, and clean the carbs. (just did this on a buddies pontoon boat)

 

[JJinSC]

Thanks, I figured it might be something like this.

 

[LouDoo]

I had a similar problem with a Mercury 2-stroke, so you're not alone, I'll admit I didn't know about the problem until I traded for a new 4-stroke.

Lou

 

[JJinSC]

The real challenge I have is going to be replacing the line to the in- hull tank. Not sure how easy that is going to be. There is only a small acces portal over the pickup unit. Hopefully, I can duct tape the new line to the old a pull it through easy enough.

How easy is it to clean the yamaha carbs? I guess I need to start looking around for a service manual.

 

[JJinSC]

Hey Dr. Honda, I am thinking about attempting to do the carb job on my 90HP yamaha outboard myself this year. It started coughing and spitting at idle and cutting off. Occasionally it acts starved for fuel. Best I can find the carbs have not been touched in 10 years. Is it pretty simple? Any adjustments to worry about other than idle? Is it just take apart, clean and re-assemble with kit or is there other adjustments or tests (like pop-off) to have to deal with? It looks pretty simple to get the carbs off. I just want a little foresight before I dive in to more than I can handle.

Thanks.

 

[Dr Honda]

Never played with a Yamaha outboard. BUT... it should be a simple side draft carb with a float in it. Shouldn't be too hard.

 

[JJinSC]

Never played with a Yamaha outboard. BUT... it should be a simple side draft carb with a float in it. Shouldn't be too hard.

I'm sorry, I thought I had read earlier in the thread that you had helped a buddy with his pontoon boat. Not to sound to uneducated, can you explain what a "simple side draft carb" is ?

Thanks

 

[Dr Honda]

Yes I did. But it was a Merc engine... not a Yamaha.

Since that post... I looked up your engine, and it's almost the same thing as my buddy's 25 hp.

The carbs on our PWC are pressure regulator carbs. They are giant weed-eater carbs. They can work mounted in any direction. The "Float bowl" on a PWC carb, is a sealed chamber, and it "Regulates" fuel via a diaphragm. The carb on your Yami engine has an actual float... and is a gravity system. (Think about how a toilet tank works) The level drops, and more fuel comes in.

Anyway... it's not a complex carb. Just yank it off, and clean it.

Last thing... on our PWC carbs... we are concerned about pop-off... with your Yamaha... you will be concerned about float level.

 

[JJinSC]

Thanks, This is extremely helpful and I can't thank you enough for the info. I think I may pay to download a shop manual for my motor. One more question. Pop-off is usually regulated by different springs, correct? What affects the float level? Is this something that will get off by just removing and cleaning. What is used for reference/checking the float level. I am sorry if these are elementary mechanic questions. I am mechanically capable, but I have always gravitated away from messing with carbs. Just always been a little scared of messing with them. The PWC carbs were not that bad though.

Oh, just thought of one more question. Is a kit needed or just clean them and put them back together?

 

[Pacoson]

I have a 1990 200HP Yamaha outboard. If you said they haven't been touched in 10 years or so you might want to get the gasket kit.

Paper gaskets might tear. I think the float bowl uses a cork gasket.
I agree that a download for the carb will answer some of your questions.

The float level is adjusted by a lever and spring like the seadoo, it just has the "float" that opens or closes the needle valve.

 

[Dr Honda]

Thanks, This is extremely helpful and I can't thank you enough for the info. I think I may pay to download a shop manual for my motor. One more question. Pop-off is usually regulated by different springs, correct? What affects the float level? Is this something that will get off by just removing and cleaning. What is used for reference/checking the float level. I am sorry if these are elementary mechanic questions. I am mechanically capable, but I have always gravitated away from messing with carbs. Just always been a little scared of messing with them. The PWC carbs were not that bad though.

Oh, just thought of one more question. Is a kit needed or just clean them and put them back together?

Basically... you just bend a tab to set the level. The manual will tell you the measurement, and where to measure from.

If you are careful... you can get them apart, and not need a "Kit"... but you will need a new base gasket. (at the minimum)

 

[JJinSC]

Ok, I order the kits for the carbs. I'll be picking them up tonight or tomorrow. Do you think the container full of cleaner you can buy from the parts store or wal-mart with the basket in it will be alright for the aluminum carb parts or should I just spray them off and out real good with typical carb cleaner? I read somewhere that some manufacturers now do not recommend the soaking method due to a special treatment they put on the aluminum at the factory. Just wondering if this should be a concern.

 

[JJinSC]

One carb down, two to go. That one was pretty easy except for getting the float valve brass jet out. Wrench will not fit in there. A socket does not fit well and the brass wanted to start giving, but I WD40'd it up real good and finally got it loose. I was sweating. I talked to a certified yamaha tech at the local dealer and he said soak them, so I went the soaking route. Had to soak just over an hour for it to be real easy. That chemical takes a little longer to dry than regular carb cleaner. I blew everything as dry as I could with the air compressor. It finished drying pretty quick after that.

 

[Dr Honda]

yep. The old carb dips was great... but the new stuff isn't as powerful.

You still want to use a carb spray, and compressed air once you get them apart.

 

[JJinSC]

I got 'er done. All put back together and fired up in a split second. She is running like she is suppose to now. No more coughing and sputtering at idle. Thanks for all your help!!!

 

[Dr Honda]

Glad it wall worked out. :thumbsup:

 

[JJinSC]

Well, the boat ran good for two weeks, but those were shorter outings. Yesterday, the family went out on an all day boating trip. ABout a sixty mile trip down river tubing,etc. This was the first time the boat has ran this long since I rebuilt the carbs. About 40 minutes into the trip, the motor started acting like it was starved for fuel. I could let off of the throttle back to idle and it would idle fine. I could then go again it would run for about another 20 minutes or so and do the same thing. If I waited too long to pull the throttle back the engine would cut of like it ran out of fuel. So, I checked the bulb on the fuel line and it was empty. I hand pumped the bulb until it was tight and the engine would run again fine for another 20 minutes or so. I thought maybe it was the fuel vent clogged, so I opened the gas capped and it still exhibited the same behavior.

Here is what I have done:
- Replaced water separator filter (10 micron). Poured contents into glass container. No water present. Filter had caught very little debris.
- Replaced fuel line,bulb and connecter from water separator filter to engine.
- Inspected internal fuel lines and cleaned fuel filter under cowling.
- Rebuilt carbs with Yamaha kits.
- Adjusted idle and pilot jets according to manual.

Engine ran fine for two weeks. The weather was 10 degrees hotter and 100% more humid the last two days. Later in the evening yesterday, when the weather cooled off, this symptom almost completely disappeared, but I also did not have the Bimini top up nor was I pulling a tube.

I suspect this is a problem with the fuel delivery and not a carb problem. The bulb is never tight and when I pump it tight the engine runs fine again for a while. Could this be a fuel pump problem or do you think the system is drawing air somewhere in fuel line from tank to engine? What should I do next to trouble shoot?

Thanks in advance for any help.

 

[Dr Honda]

Yep... sounds like delivery to me.

Does your engine have a pump to draw the fuel... or is it a pressure system?

If it's a pump... look for an air leak in the lines coming up to the pump... and make sure the pump is OK.

If it's a pressure system... pressurize the tank, and find the leak. Also... if it was a pressure system... did you make sure the fuel cap was tight?

 

[JJinSC]

Yeah, The motor has a fuel pump. Here is what the shop manual says so I guess I'll takle this this week as well as inspect the line coming up to the pump.

Fuel Pump:
1) Using a screwdriver, disassemble the fuel pump.
2) Visually inspect the pump body for cracks and replace if required.
3) Inspect the valves for cracks or distortion and replace if required.
4) Inspect the diaphram for sign of damage, perforation or stretching and replace if required.
5) Assemble the fuel pump with new gaskets.

 

[JJinSC]

Opened the portal above the tank and found this. Do you thing this could be my problem or is this just cosmetic? it still felt strong when I tried wiggling it and everything looked still good and sealed. Either way I plan on addressing this. But would like to know if you think this could be my problem before I spend $100+ dollars on an external tank rig to get me through the holiday and weeks to come and make this a fall project. I have checked all hoses from where the fuel attachment is on the front of the motor to the carbs. I have not yet disassemble the fuel pump because I want to wait until I have a kit for that.

Any idea if there is a nut under this pickup or do these just screw straight into the plastic tank?

 

[Dr Honda]

Sorry... no idea on that one. BUT... I think it's got a long tube on the other side. So... if you take off the hose... then you can unthread it, and pull it out to see if it's plugged.

 

[JJinSC]

I did some searching and found a key west boats forum. I found someone had posted pictures that looked just like this with the exact same symptoms on the same model (but earlier year). Turns out there is a check valve in that elbow right where the hose attaches. I think it is highly possibly my problem. I just hope that nut is strong enough to hold up to me unthreading that elbow. The other guy also said this was difficult due to the small portal to access. This does not look fun to me at all. I am really feeling depressed right now about this one.

Thanks a ton for your quick response though. I think I will hit Basspro first thing in the morning and get an external tank for tomorrow.

 

[JJinSC]

Hooked up an external tank and ran all day today with no issues. So, so I can start planning for this fall project, considering the corrosion on this elbow and tank fitting, how would you start at trying to remove it?

 

[Dr Honda]

Well.... if that turns out to be the prob... make sure you let us know. That way I'll know next time.