replace all Yamaha carbs Chapter 2

[colayn]

Guys, some of you are familar with my first post "replace all carbs" last week.
I now have the boat back after paying $275 restocking fee for the carbs, which they still didn't have one of.
Mad as hell but not worth a fight.
I have been through the carbs and they are as clean as can possibly be. I even ran the fluid test thru the inlet line and the flow from all 6 jets is as consistent and straight as it could be. I tried high pressure and very low pressure and flow is great. No stop, starts and no erractic movements in stream.
100% confident the carbs are good. But I really need help finding root cause.
I put 2 new fuel pumps on it when this all started and didn't help.
Could I possibly have gotten a bad one from Yamaha?
How can I test it ?
How can I find a vacuum leak in the fuel system ?
Can a prime bulb be the problem ? Maybe restricting the flow?
I have taken the fuel line out of the tank and intake and filter are clean.
Again it starts easy, runs smooth but will only turn 4800 RPM and use to run 5800.
I REALLY appreciate you fellows helping me solve this. Been without a boat since Sep. and the fish are biting here.
Thanks,

 

[99yam40]

Re: replace all Yamaha carbs Chapter 2

are you sure that you are not getting enough fuel to all cylinders as you said they told you? If so then test the fuel supply system with a pressure /vacuum gauge.Testing is always better that just guessing on all parts of the motor.
http://forums.iboats.com/showthread.php?t=283363

If not then start from scratch and make sure the compression is good on all cylinders and there is good spark on all too. make sure the timing is doing what it is suppose to at all times especially at the problem rpm along with the spark. If all is well with that then look at the fuel.

It took me about a year to finally figure out a previous owner of my motor apparently drilled out the main jets( trying to make a 50 out of a 40 is my guess) causing it to drop a cylinder at wot but ran OK other than that.
Not sure but I believe your carbs have different size jets in the different ones and if you do not get them where they are suppose to go it could cause problems too much on some and not enough on others. So make sure you know for a fact what the problem is, trusting something someone said for a fact will run you around in circles

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

compression is good, I checked it at 120 on every cyl ,,except one which was 115
The primary reason I suspect fuel delivery is you can spray fuel into it at wot and it will pick up

 

[99yam40]

Re: replace all Yamaha carbs Chapter 2

on all or just some cylinders?
And have you seen this or did they tell you this?

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

I checked compression myself and got pretty much the same numbers as they did on the work order.
As for spraying the fuel, I am going by what they did to conclude it was in the carbs.
I have had a friend run the boat while I try to squeeze the prime bulb and it doesn't help. Is that a good test for bad fuel pump ?
How can I find a tech who is Yamaha fuel system certified? Learned in my last post from Rodbolt that sometimes certified only means watching a Yammy video.

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

what transpired between the last time it turned 5800 and the first time it only turned 4800?

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Rodbolt, I appreciate you sticking with me thru this mess.
OK here goes the history.
I bought the boat in May and it ran great. About August went fishing one morning, started fine and low rpm ran fine and when I went to get up on plane it and no power. It surged , stalled and real slow to plane out. Once on plane
I floored it and it take about 2 miles to go from 4000 to 4800 RPM and wouldn't go any further.
I check filter , etc and all was good. Then I bought 2 new Yammy fuel pumps and did not help.
After that I torn down all the carbs and they were very clean. Bought new gaskets and reassembled. No change.
Take it to the shop, the first time they decarbed and put it new plugs. They said the old plugs were the wrong heat range.
Went to the lake and right out of the ramp it would do 5600, not like before but running much better.
Stopped fished and 45 min later it would only do 4800 WOT
Siponed all gas and replaced. No change
I pulled all the plugs and looked in each cyl. 5 were wet, 1 was very dry.
Went back to the shop. They adjusted floats on carbs. Went to lake no change.
From here it picks up from the previous post were they said it needed 3 carbs.
I am now headed back to my garage and rechecking the carbs very close and installing.
Then plan to check fuel lines again and run some concentrated Seafoam thru out of desparation.

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

dont get desperate.
DO repost the full engine model number.
first thing we gotta do is determine is it fuel or ign.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Here is the number just as they are on the tag
P150TLRX
6J9 L 502428
U
Also I forgot to note, when I went thru the carbs I dipped them in automotive carb dip, which I later learned is a no / no on these carbs

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

I doubt you hurt them. most carb dips now are to weak.
P150TLRX
tells us its a pro model, typically used on bass boat applications.
150 HP
trim and tilt
20" shaft
remote control and a 1999 year model run.
it also uses YMIS. also known as smart engine management.
2 pulser coils and a crank position sensor to fire 6 plugs.
do you have the correct service manual?
do you have a multimeter?
do you have a trusted helmsman thats not on your life insurance policy?

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

I have a multimeter and know how to use it

I have a general purpose service manual that cover many years of Yammy engines on CD but it is very hard to use
Tell me what service manual to buy and I will get it.

As for the helmsman, it doesn't matter, now $725 into it and still not fixed they wife is going to kick me out anyway. Almost to the point of "the boat or me"
That is a WHOLE other topic.

I am currently putting the carbs back on and running it and checking this forum.
Will post after I am done to let you know how it starts and runs on the hose.
Keep it under 2000 RPM on the hose , right ?

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

running any outboard above 2000 RPM on a flush device with no prop load is worthless at best and catastrophic at worst.
but you have to determine if its a fuel issue or ign issue.
always remember, its suck,squeeze,bang then blow.
yes its that simple.
the correct amount of air to fuel.
the correct amount of compression on the above
the correct spark timing for the RPM its going.
the ability to remove spent gas.
if all the above are correct it simply runs as designed.
if one is missing it simply does not.
its not Voodoo.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Rodbolt,

Carbs are back on and it started right up and running fine on the hose.

You didn't tell me in the last post the best service manual to buy.
I am going to be out of town until Wed. and I don't think I will have internet access.
This post will be old by then, will you still check it ?
Would like to know what to do next.
I will take it to the lake before I post again just to see what is current
Thanks,

 

[Don S]

Re: replace all Yamaha carbs Chapter 2

Not sure if it will help you guys or not, but here are some specs for that motor.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Thanks Don S, all input is appreciated

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

and note the yamaha test wheel YB1626 reference?
also the IDC dyno RPM and pressure references?
both can be used.
on the electrical tests, I typically use the loaded output voltage. about the only resistance test I use for general testing is the plug caps.
note that all voltages are peak, not true RMS, this requires a peak reading meter or a DVM with a DVA adapter.
maximum fuel system vacum measured at the lower lift pump is 4" hg, much more and it will lean out all 3 fuel bowls.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Got everything put back together and take it to the lake. Running just like before.
One thing I did notice that should tell me something, but I don't know what.
Whenever I start out on a new run it will go up to 5200, then fall back to 4800 and will not go back up to 5200 until I stop and start over.
WOT and 4800 and I can feel it surging and dying back.
Also I pulled the plugs out (new plugs) and all had the same tan color except the one on the port side, bottom cyl. The ceramic around the electode was a lot whiter than the rest.
Any idea were I should start working ?

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

your still down on RPM. either find the fuel issue or fix the electrical issue or you will post about compression issues.
the white one is either not getting fuel, not fireing or has water in the cyl.

 

[jeffersondodson561]

Re: replace all Yamaha carbs Chapter 2

Have you verfified that the carb throttle plates are opening "horizontal" at wide open throttle? Take the airbox off and WITH THE ENGINE OFF push remote control handle to wide open throttle and look at the throttle plates they should be horizontal if they are not need to adjust, recommend a good sync and link, verify top dead center and check wot timing.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

I have checked the throttle plates are wide open with engine off
Could it be different when running
I have never seen a Yamaha service manual. Are they fairly easy to use if you don't know all the termanology?