115TLRD Rough Idle and Power loss at high RPM

[jduque_99]

Hi and Thanks in advance to any one who can provide me with any help. Here is my situation. About a month ago I was having problems getting the engine started the first time that I would put the boat in the water for the day. After the first start, then it would fire up no problem at the first turn of the key. I figured my carbs were dirty, so I cleanned them and now the engine fires up without problem.

The Engine: 2005 YAMAHA 2 STROKE MODEL 115TLRD

The problem: Now the engine Idles rough in neutral and sputters almost stalling from time to time unless I increase the RPMs. When I put it in gear and increase the throttle, the engine initially responds to the increase in power, but it loses power almost immediately and stalls if I don't reduce the throttle to a no wake speed. Anything over 3,500 RPM will cause this condition. It is almost like if it was not getting enough fuel. The hoses are all clean and intact.

So the only thing that I can think is that I must have done something wrong while reassembling the carbs, but can't figure it out. What did I do wrong? Any advice or technical information will be appreciated.

Once again thanks in advance for any help provided.

[99yam40]

Did you follow the link and sync procedure in service manual when reinstalling the carbs after cleaning to make sure all linkages, timing, and adjustments are set properly?

[jduque_99]

I don't own a service manual. I thought I could do without. Obviously not . Will get one and see if I can trace the problem while following the instructions this time. If anyone has any other advice I would still like to hear it. Thanks.

[throrope]

If your 150 is configured with similar fuel system as ours, the electric choke and emergency fuel enrichment which is on my middle carb only may have been patient zero, but only a symptom of a greater need for carb clearing.

IMHO, you are experiencing a repeat of the original problem as I had some time ago on our 90 tlr. After the third time through the carbs, thinking it was ignition, I gave up and took it to the dealer. They rebuilt the carbs, but qualified their repair unless I tossed the gas and cleaned the system. Best explanation was contaminated gas. Or in other words, a repeat problem with every trip unless corrected. I found it cheaper to replace the fuel system - tank, bulb, filter and lines. No issues since.

Here's a link to the factory service manual order site. YAMAHA MANUAL STORE
They pay for themselves with the first use.

[jduque_99]

This may be a little lengthy but please stay with me. I can really use the help.

Well, I got the Service Manual and getting ready to target my problem again. But before I begin I already have a couple of questions and would like to ask for some help getting some clarification before I start.

The Disassembling The Carburetor section of the manual states: Before disassembling the carburetor, make sure to note the number of times the "Pilot Screw" is turned out from the seated position to its set position.

Problem 1: I have read the manual top to bottom and nowhere in the schematics is there any reference to a "Pilot Screw". There is a few possibilities on the Carburetor Schematics but I don't know which one is the right one for sure so I will list them referring to the Part# on the Carburetor Schematics and its name.
* Part 11 - Pilot Jet Plug
* Part 12 - Pilot Jet
* Part 19 - Pilot Air Jet
* Parts 3, 13, 15, 17, 20 - Screw (multiple locations)

Problem 2: When I first disassembled the Carbs, I did not pay attention to the position of the so called "Pilot Screw", so now everything is just tight and I don't have a point of reference for what the proper set position of said screw would be. Where can I find what the right number of turns would be from the seated position to the set position.

Once again. Thanks in advance for any help provided. Like I said before, I really am in need of it.

[99yam40]

If your 150 is configured with similar fuel system as ours, the electric choke and emergency fuel enrichment which is on my middle carb

throrope
Your motor should not have electric choke and an enrichment system.

You should have the prime start system that enriches the fuel during cold start

[99yam40]

This may be a little lengthy but please stay with me. I can really use the help.

Well, I got the Service Manual and getting ready to target my problem again. But before I begin I already have a couple of questions and would like to ask for some help getting some clarification before I start.

The Disassembling The Carburetor section of the manual states: Before disassembling the carburetor, make sure to note the number of times the "Pilot Screw" is turned out from the seated position to its set position.

Problem 1: I have read the manual top to bottom and nowhere in the schematics is there any reference to a "Pilot Screw". There is a few possibilities on the Carburetor Schematics but I don't know which one is the right one for sure so I will list them referring to the Part# on the Carburetor Schematics and its name.
* Part 11 - Pilot Jet Plug
* Part 12 - Pilot Jet
* Part 19 - Pilot Air Jet
* Parts 3, 13, 15, 17, 20 - Screw (multiple locations)

Problem 2: When I first disassembled the Carbs, I did not pay attention to the position of the so called "Pilot Screw", so now everything is just tight and I don't have a point of reference for what the proper set position of said screw would be. Where can I find what the right number of turns would be from the seated position to the set position.

Once again. Thanks in advance for any help provided. Like I said before, I really am in need of it.

I take it this manual you got is not the one from Yamaha for your motor as they give the specs

What did you get?

[jduque_99]

I take it this manual you got is not the one from Yamaha for your motor as they give the specs

What did you get?

I got what the YAMAHA MANUAL STORE said was the appropriate manual for my engine( 2005 - Two Stroke - 115TLRD)

Service Manual LIT-18616-02-72

Should I have gotten a different one? Suggestions

[throrope]

Yea, same here and I thanked boscoe99 on this recent thread:
http://www.yamahaoutboardparts.com/f...s-th22691.html

The pilot screw is the old idle air screw that on mine is externally accessible and located closest to the manifold. As I understand, thanks to the EPA, is under a push in cap. The orangutan at the prior owner's dealer had that and every other linkage miss adjusted. Rudy Marine in Wilmington DE made all right for me and installed the caps. The pilot air jet is a conical needle that as it opens from seated adjusts the right air/fuel mix at idle. Per boscoe99 for my 90 tlr, 1-1/4 turns out from light seat plus/minus a quarter. I suspect near the same for all Yamaha two-strokes.

BTW, on our 90 TLR, per the service manual, all linkages can be correctly adjusted from marking on the motor using only hand tools.

IMHO Yamaha two strokes were built for those who depend on them to put food on the table. Too bad the EPA and ethanol put an end to them here. On the other hand, their four strokes are just as reliable and drink much less gas. Here in the OBX most run Yamaha because we don't like working on weekends.

[throrope]

throrope
Your motor should not have electric choke and an enrichment system.

You should have the prime start system that enriches the fuel during cold start

Yup - Thanks. I couldn't remember the right description.

[99yam40]

I got what the YAMAHA MANUAL STORE said was the appropriate manual for my engine( 2005 - Two Stroke - 115TLRD)

Service Manual LIT-18616-02-72

Should I have gotten a different one? Suggestions

It will have the specs in the specification area(charts)

[jduque_99]

Yea, same here and I thanked boscoe99 on this recent thread:
http://www.yamahaoutboardparts.com/f...s-th22691.html

The pilot screw is the old idle air screw that on mine is externally accessible and located closest to the manifold. As I understand, thanks to the EPA, is under a push in cap. The orangutan at the prior owner's dealer had that and every other linkage miss adjusted. Rudy Marine in Wilmington DE made all right for me and installed the caps. The pilot air jet is a conical needle that as it opens from seated adjusts the right air/fuel mix at idle. Per boscoe99 for my 90 tlr, 1-1/4 turns out from light seat plus/minus a quarter. I suspect near the same for all Yamaha two-strokes.

BTW, on our 90 TLR, per the service manual, all linkages can be correctly adjusted from marking on the motor using only hand tools.

IMHO Yamaha two strokes were built for those who depend on them to put food on the table. Too bad the EPA and ethanol put an end to them here. On the other hand, their four strokes are just as reliable and drink much less gas. Here in the OBX most run Yamaha because we don't like working on weekends.

Thanks throrope. I will look around to see if I am missing something, but I cannot see anything similar to what is referred by boscoe99 on the schematics I have on my manual. Also I didn't messed with anything resembling what its being described when I cleaned the carbs the first time. I really am at a loss right now. I am attaching a pic of the schematics in my manual, it also has the numbers of the parts I referred to previously. Hopefully someone can see something I am missing

[99yam40]

SCREW, AIR ADJUSTING #21 in part break down and should be under #27 that has to be removed to get to it. You did not take the carb apart and clean all passages if you did not remove any of this

[jduque_99]

It will have the specs in the specification area(charts)

99yam40. The specification area does mention my engine type. Please don't take this the wrong way. I don't mean to be rude, and I appreciate all the advice I am being given by everyone. But the only thing I am sure at this point is that I did get the right manual for my engine model and year according to the YAMAHA MANUAL STORE, and that except for the one statement on the manual that I mentioned before, there is no reference to the "Pilot Screw" in any schematics or anywhere else in the manual. I have attached a picture of the Carburetor in a previous post. Hopefully someone can see something I am missing.

[rodbolt17]

should be about 5/8ths of a turn out.
the pilot fuel and pilot air jet control the A/F ratio.
all that screw does is allow more or less of this A/F mixture into the passages.
did you check the fuel pump while you were at it? they don't last forever and they hide debris.