Not running well above 2000 rpms!!

[Jamie D]

Just bought the boat, the last owner bought the motor rebuilt/used, so the complete history of the motor is not known. The motor cover is a yamaha 175, It is a 2 stroke. I'm not sure if it is a 175, as the carbs are # 6501 ( which my manual says is for the 225 hp 90 degree V6) Also, it has a throttle position sebsor, which I recall reading somewhere is only found on the 225 and 250 hp models. Don't know for sure what my motor is, so I'm at a loss as to check and sync weather for a 175 or 225 hp. Also the motor is stamped 6R500...
As for my problem with the motor, it does not run well above 2000rpms. It bogs for about 8 seconds, picks up rpms for about 3 seconds, then falls back down again.
I did a compression check, it has about 120psi at all cylinders except 1, which is @ 102 Psi, I just replaced both fuel pumps, gas is fresh, H2O seperator is clean/clear of H20. I rebuilt and cleaned the carbs, adjusted the floats etc.
One thing I noticed today is the the top carb is not really sucking much air while the motor is running, def. not the same volume as the bottom 2 carbs. Also, it has a intermitent miss at higher RPMs.
Could this be a reed issue?

 

[waffles1]

Re: Not running well above 2000 rpms!!

Hi jamie D.
Is your fuel bulb staying hard and full when you are having these problems? Does pumping it help?

 

[Jamie D]

Re: Not running well above 2000 rpms!!

yes bulb stays hard, pumping does not help...
Thanks

 

[Jamie D]

Re: Not running well above 2000 rpms!!

Oh come on! Somebody? Rodbolt, what do you think?

 

[krisnowicki]

Re: Not running well above 2000 rpms!!

I did a google search on the heads and it said they were used on excel engines. Do you have any pics

 

[Jamie D]

Re: Not running well above 2000 rpms!!

I did a google search on the heads and it said they were used on excel engines. Do you have any pics

I'll try to get some pics tomorrow.. Thanks for the help so far guys, in the mean time, let me know if you guys have any other thoughts

 

[rodbolt]

Re: Not running well above 2000 rpms!!

I think you have a blown up franken motor.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

I think you have a blown up franken motor.

I guess that response was easier then actually putting any thought into the problem.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

I'll try to get some pics tomorrow.. Thanks for the help so far guys, in the mean time, let me know if you guys have any other thoughts

Sorry guys, I was not able to get pic's today. Will have to wait till next week, Will be on a surfcamp trip with my son for the next 5 days..
Thanks again

 

[99yam40]

Re: Not running well above 2000 rpms!!

I guess that response was easier then actually putting any thought into the problem.

Low compression on a motor that may have parts from different motors and you have no idea what motor is really is.
sounds like a Frankenstein motor that is blown up to me also.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

as far a miss match of parts, agreed, except, I have a feeling that just the cover of the motor is the enigma, not the motor as a whole. (I hope I'm right on that, as I don't have much need for a hybred/inbred boat motor).
As far as the compression is concerned, is 120+/- on 5 cylinders and 102+/- on 1 cylinder a big difference?

 

[99yam40]

Re: Not running well above 2000 rpms!!

Usually say they all need to be within 10% or 10 PSI.
Something is causing it to be low, you need to try to find out what. Bore scope would be nice to look inside cylinder or pull head. But that is just my opinion.

 

[rodbolt]

Re: Not running well above 2000 rpms!!

its a big problem.
a 2 stroke v6 is simply 6 motors sharing a common crank
any more then 10 PSI difference is an issue.
over the years many 2 strokes have used the TPS.
gotta have pics,then prolly more pics,
did not require much thought your the one that posted its blown.
either a cyl/piston or a gasket let go.
I cant see it but you can.
pics of the fwd port side may help.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

Here's some pic's. I'm pretty sure it is a 225, don't know year or model
Here is the deal, originally the motor would not run above 2000 rpms, have an alarm (horn) going off under the dash. Gauges check out good, oil resi. is full, alarm goes off even on first start up before motor has any temperature.
Now the motor will not start unless I disconnect the 14 pin connector below the cdi, will only shut down once I reconnect the 14 pin connector. As far as the alarm, I can leave the boat sit for days, and once I turn the key on, the alarm goes on... I am going to check the oil resi. tomorrow, clean etc.
Also, I visually check the ground from the battery, back to a "junction" post and then to the starter. Had good, tight connections all the way.
I want to get the Family out on the water so bad, this is getting frustrating!

And by the way, Rodbolt... I have read and read many of your post, if you were within a half days drive from me I would make the trip! Thanks for all your insight guys

 

[Jamie D]

Re: Not running well above 2000 rpms!!

The alarm is still going, I traced it back to the pink wire at the 14 pin connector at the motor. I disconnected the wires for the premix oil tank thinking a sensor is bad, no bueno, alarm still on. Still not sure what the alarm is trying to tell me.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

Small update, the motor will start for maybe a second (or less).
I tried holding the key on, but the solinoid on the starter drops as soon as it fires.

 

[rodbolt]

Re: Not running well above 2000 rpms!!

check for 12V at the yellow connector at ECU, post a clear pic of the ECU.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

Here you go, checked, yes it does have 12v. Are they supposed to be looped back together like that?

 

[rodbolt]

Re: Not running well above 2000 rpms!!

franken motor.
yes the yellow wire is looped but not with the yellow/red. where does that yellow/red go?
if you unplug it it goes into bypass mode and locks timing at 7*BTDC.
you have a 93 to 95 225 2.6L.
check all plug caps, you can use the diagnostic test lamp to check for codes.
get a better shot of that snakes nest wiring on the stbd side.

 

[Jamie D]

Re: Not running well above 2000 rpms!!

Rodbolt,
Hope this picture is what you are looking for.
That yellow/red wire goes up to the counsel, and dead ends.. it's not hooked up to anything..
In what way do I check the plug caps, what am I looking for.
How do I get codes with the test lamp.
One more thing, if I disconnect the 14 pin below the ecu, the motor will start, but will not turn off with the key, only when I reconnect the 14 pin will the motor shut off.