2004 txrc 150hp power loss

[Clownfish]

Just bought a used 2004 TXRC V6 150hp (Carbed), only about 50 hours on the motor

Will only get to 2800-2900 RPM . Seems to work fine to that point, and then stutters a bit when you go past half throttle and then slows down a little. Used an external tank with new fuel to rule out venting issues on the boat fuel tank and ensure "good gas", patched it in just after the bulb on the current system (just before the wiring harness into the motor), didn't change anything, tried pumping up the bulb too, also no joy.

Checked the compression, all six cylinders were within 110-117psi

I don't think the LP fuel pumps have ever been replaced.

I have taken it to a mechanic, but he hasn't had a chance to look at it yet. From my reads on this and other forums, my chief suspects would be still be fuel starvation issues (blockage in another part of the line, LP fuel pumps, or clogged carb parts) and after that ignition issues. Maybe the alarm without the alarm horn?

(BTW, how do you check to see if your alarm horn is working or not?)

Anyway, is there anything else to check first? Any advice on talking to my mechanic about this issue?

Thanks in advance,

Clownfish

[jb123]

dirty carbs
dirty filters
plugs
lift pumps
check valve? not sure if you have one
air leak
whats the ball cond when this happens? filter level ?

[Clownfish]

dirty carbs - yep could be!

dirty filters - nope only filter in the line is clean

plugs - possible

lift pumps -are these the LP pumps?

check valve? not sure if you have one - neither am I - does anybody else know?

air leak - where do you look for this? you mean "air" sucking into the fuel line?

whats the ball cond when this happens? do you mean the "bulb" for pumping up the fuel? It is hard, and I tried keeping it that way with an external tank, didn't change anything.

filter level ? if you mean what was the fuel level in the filter while under power, don't know yet....

[Clownfish]

Well the mechanic has cleaned carbs and adjusted fuel to one of the cylinders.

Still has the same issue.

He now thinks it may be in "protection" mode, but there is no alarm. I've asked him to check the horn by pulling the dead-man's lanyard and turning on the engine. But can the motor go into protection mode without sounding the alarm?

[99yam40]

Did you take it to a Yamaha shop?

I do not under stand how they would clean carbs and only adjust one carb
They all need to be link and synced after reinstalling the carbs and adjusted to factory specs

It is not realy a protection mode, just that it limits RPM and lets you get out of harms way so you can shut it down. And it should always sound the buzzer.
I believe the timing is retarded to limit RPM, so easy to check

[Clownfish]

No, not a true Yamaha shop. But the guy has VERY excellent recommendations from some long term boaters I really trust ......but I must admit I am second-guessing that decision.

They were supposed to test the horn/buzzer today....not sure how that went.

I cannot say if they adjusted more than one carb or not, they may have been rebalanced, but they did say that one cylinder (carb) was "off" at the outset.

They suggested that the RPM limiter could engage without the buzzer/horn if the temp or oil seniors were "bad/broken" but not necessarily giving a fault reading.....

But my RPM's were up to 2700-2900 - isn't that higher than the limp mode? But can I trust the analog gages? I know they are showing the trim at the wrong level, the fuel gage seems a little flaky too.......

[Clownfish]

So, since the motor is at a non-yamaha tech, can they buy the correct diagnostic equipment anyway? Do these older (2004 TXRC carbed models) need it?

Is there one or two questions I can ask them that would tell me 1) yea, this guy can probably do it or 2) cut your losses and go to a true yamaha shop?

[Clownfish]

No thoughts on questions to ask?

[Clownfish]

So it was not the alarm, system and buzzer checked out fine.

Original mechanic decided that I needed a yamaha tech, or was just frustrated by the motor or maybe just frustrated with me, but the short story is my boat is at a yamaha dealer with a guy that's says he knows these motors really well, and seems quite confident, as is "yamaha factory trained." They'll get to it pretty soon, keeping my fingers crossed.


Will let you know what happens!

[Clownfish]

So the new Yamaha mech want to take a "take no prisoners" approach.

He agrees it's a fuel problem, and basically says there is ethanol related debris (degraded rubber/polymers and even some corrosion) in the carbs.

So he will rebuild the carbs and replace the fuel system/lines from the tank to the carbs, including the LP pumps, filter housing, tubes, etc., and install a fuel/water sep too.

A bit more than I had hoped to pay, but I'd rather not have the same issue again next year.....

I'll report back how it goes when it's done in about 9 days......

[99yam40]

See if he will agree to you not having to pay for all of this if that does not fix your problem

May not be a good idea, he might charge you even more for the guarantee

[Clownfish]

well good news finally the Carb rebuild and fuel system replacement worked, motor ran great. starting with a clean slate, now to ward off ethanol damage as I move forward....... .

[jb123]

just ward off using ethanol....