2004 Yamaha 2 stroke

[Timguy]

Hi, I got this motor in on trade in and it needed work. Hooking up a new fuel tank and line to fuel filter, then replacing punky line between fuel filter and pump. Got out broken off low speed needle in one of the carbs and replaced it. Set at about 3 1/2 turns and motor runs great. Also cleaned out fuel pump and made sure the reed valves were centered over ports........they will not line up properly if you expect the pegs to ensure the alignment. Diaphram looked good.
Problem is that under full speed only and after at least a 4 minute run......the motor will run lean and slow down until you pump the sqweeze bulb. Then will recover and run ok for another minute or two. I tried 3 different tanks and also rechecked the fuel filter and pump. No leaks or flattened hoses while running or at rest. My guess is that the fuel pumps are typically engineered close to the edge and maybe cant suck hard enough to gain fuel supply from a fuel tank with a 12' hose. I have added hose length to most of my motors but maybe this won't work on this particular application. Some of my OMC's pull through a 20' 3/8 or 5/16 hose.
What is going on? Maybe just a weak pump? Customer is frustrated and soon will ask for a refund if I can't get this problem resolved. The motor is very low hours and almost like new. I sold it to him for $1,600. Thanks.....Tim

 

[99yam40]

Re: 2004 Yamaha 2 stroke

Is there a reason you have not tested the fuel pressure/vacuum to see what is going on?

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Well, yes......the problem is apparent. I have low fuel supply at the carbs and just trying to pinpoint the problem. The fuel tanks work fine on other motors so I can safely eliminate them as the cause. Fuel pressure itself may be low as well as the supply. I use high quality auto or marine hoses for my replacement units. Perhaps there may be a problem with the fuel filter, as you may know.....it is a cartridge/screen design and pretty simple. I am using steel OMC tanks as they are self vented when the fuel lines are coupled on at the tank. Sometimes our guests forget to open the vents on the plastic tanks and wonder why the problems????? The OMC design is pretty ok for any operator as long as they push the coupling on the right way. The steel tanks are very durable and I have lots of them around from years and years past. Thanks, Tim............any more ideas?

 

[99yam40]

Re: 2004 Yamaha 2 stroke

Well if the pump will not pump up to the proper pressure or pull the proper vacuum then it probably needs replacing. That is why you normally test things

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok then, I'll try to find the pump testing proceedure before I go ahead with a kit or replacement. I have manuals covering most OMC's and Mercs but are there any on line testing proceedures available for this model Yamaha to save perhaps the expense of more manuals? Thanks, Tim

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Perhaps no one really knows the test proceedure and output requirements for this model so I will try another forum site where I might get a reasonable response. Regards, Tim

 

[GrayBlue]

Re: 2004 Yamaha 2 stroke

Perhaps no one really knows the test proceedure and output requirements for this model so I will try another forum site where I might get a reasonable response. Regards, Tim

This link will help you test your fuel system.
http://forums.iboats.com/showthread.php?t=283363

Let us know how it turns out.

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok thanks, I've gone to school on it. Regards, Tim

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok I tested the fuel pump following the 3 steps. First step passed with no bubbles. 2nd test produced 2 to 3 inches vacuum depending on engine speed. Can't load motor as it is in the water tank. Did notice a fast fluctuation between 1.5 and 4.5 inches vacuum while engine was at an intermediate speed between slow and fast troll. 3rd test produced very good results with 5" vacuum created within 4 seconds and to a max of 7" at very fast trolling speed by 6 seconds.
In order to create the symptoms the owner describes and I have noted in opening of this thread, I would have to rent or borrow a 16" transom boat and trailer it out to the lake then run the motor for at least 4 minutes @ WOT. This is really an odd problem to blame a fuel pump with these test results. Anybody out there who has any imput for me on this one?

 

[Timguy]

Re: 2004 Yamaha 2 stroke

These pumps run $110 and available from Yamaha dealers only. My earlier inspections of the pump show no wear or defects.....they are a super simple unit.

 

[jeffersondodson561]

Re: 2004 Yamaha 2 stroke

Have you tried running the fuel line directly to the on engine fuel filter to eliminate the fuel connection at the motor? Maximum fuel pump lift height is 30" from the bottom of the tank pick up.

 

[99yam40]

Re: 2004 Yamaha 2 stroke

If it can pull 7" , I would think pump is good
and if it pulls 4.5 at fast idle I would think that if you get it up to WOT it will be over the 4 max they talked about and you have a restriction somewhere.

Tim, where did you hook the gauge into the fuel system?

Jeff, do you know if the 3.5 turns out is too much on the pilot screws?
I am not familiar with this motor, but sounds too many turns to me

 

[jeffersondodson561]

Re: 2004 Yamaha 2 stroke

 

[jeffersondodson561]

Re: 2004 Yamaha 2 stroke

I would deep six those metal tanks, depending on where your gauge is installed (should be installed right before fuel pump if testing vacuum) and if your gauge is correct. You should not see that much fluctuation in your readings. Metal tanks tend to produce more debris that can clog pick up tube screen. Assuming you are doing the test correct.

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok thanks all for reply.
Firstly, no I have not tried connecting fuel supply directly to the fuel filter, however I have tried 3 OMC steel tanks with several hose length and primer bulb changes with all the same results. No I have not tried a plastic tank or an original Yamaha tank, but these tanks I have tried on the Yamaha have been working on all my other OMC's with 25 or more horsepower. When I stop the motor with about 2.5 inches of vacuum showing on the guage, it will hold that reading for several hours until slowly dropping to 1 inch by overnight. Then I can release the vacuum by uncoupling the hose at the motor fitting. I have my very trusty testing guage spliced in right at the fuel filter inlet. The outlet of the filter has the original Yamaha hose (about 9" long) running over to the fuel pump which is bolted to the lower carb.
Rechecking the low speed needles, they are set at about 3 turns from lite seat.
The vacuum fluctuation at intermediate idle has me curious as 99yam suspects it may run somewhat too high and thus suggesting a flow restriction could be occuring and not a fuel pump issue. Is there a suggested volume amount that this pump should supply at a given RPM? Is it possible the floats are set improperly and not providing adequate fuel supply @ WOT? I set both floats to perpendicular with carb bottom milled surface.....correct? Thanks, Tim

 

[99yam40]

Re: 2004 Yamaha 2 stroke

Sorry I can not answer your questions as I do not know the flow rates on this motor, but I would not think you should be showing and holding a vacuum with the motor not running unless there is something restricting the line.
I would try Jeff's advice and bypass the quick connect as I have seen those have problems before.
Maybe hook the gauge at different points to help in point where the restriction is.

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Wouldn't the guage show some vacuum as long as the fuel tank is below the level of the fuel pump.......more vacuum held if the tank is lower and less held as the tank is higher? Funny thing is that when I got the motor.....the fuel line was run directly through the cowlimg from a fuel tank (never saw the tank). The previous owner had no information for me except that it was used on a pontoon boat and that is the way it was configured when his dad bought the motor. He said it ran fine the way it was set up without a quick coupling. I've never heard of such a problem, but then again I have spent little time working with Japanese technology.....well at least when applied to outboards. What would be wrong with using a coupling? Everybody else does it. Can I improve anything by eliminating the coupling? I'm lost now on this one....help!

 

[99yam40]

Re: 2004 Yamaha 2 stroke

Just try it hooked up straight to see if it is your problem. Any connection can have a restriction or blockage.
easy what to check it. Or hook up the gauge in different places to find the problem
A open ended tube should not hold 2.5"f vacuum unless there is a restriction.

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok pal, I'll get it done. Thanks

 

[Timguy]

Re: 2004 Yamaha 2 stroke

Ok I put another fuel pump from a good 25 Yamaha and did notice that the newer pump has a tighter diaphram than my original pump. The original was kind of "stretched out". Motor runs fine in the tank and readings are close the same as the original pump. Still holds 2 1/2" vacuum when motor is stopped. If you lift the tank off the ground and up to the same level as the fuel pump, then vacuum goes away until you set the gas tank back on the ground. That is telling me there is no "restriction".....but only the force of gravity. The pump has no trouble lifting the fuel up to the test tank with the fuel tank on the ground about 42" down to the top of the fuel in the can.
You know that if this motor still starves out for fuel when I "lake test" it I'm really going to "deep six" something......and its not going to be my steel fuel tanks. Which by the way work fine on the other Yamahas around here.