Help with a 150 V6 2002 2 Stroke --- RPMS

[Parker Boy]

My engine will not exceed 2800 rpms on the water. On land I can get the rpms highers. So far I've changed the plugs and changed the fuel/water filter(one inbetween fuel and engine). I even tried pumping the bulb while going on the water to see if maybe the bulb had a crack and air was getting in ...

The problem still exists. Engine starts OK. I idles ok. When I start going and give it some throttle, the boat seems like it's going to take off, then backs down. If I go full throttle, it stays at 2800 rpms.

People have made suggestions like the O2 Sensor(I don't even know if I have one?) or maybe even a pump.

Any suggestions would be appreciated.

Thanks.
Tony

[boats.net]

You need to do a compression check on engine. When you pumped the primer bulb did the engine run worst? If so check the fuel pump diaprams. If it's a HPDI or OX66 model then check the medium and high pressure fuel pumps, will need to hook up to Yamaha diagnostic computer system for HPDI's and check the warning buzzer, if warning is activated the engine will hold at about 2000 rpm's.

[Parker Boy]

Thanks for the reply. It's not an HPDI. When the bulp was pressed, there seemed to be no difference in running(no better, no worse). No warning buzzers or lights seem to be happening. Should I assume warning lights are on the motor and not the dash? (sorry if that sounds naive, that's because I am when it comes to motors).

Assumpion number 2, the only way to hook up to a Yamaha diagnostic computer is to take it to a Yamaha dealer(and service)?

In searching the net, for similar issues, there has been a mention of the ECM getting a loss of input from somewhere and the ECM limits the engine. Basically putting it in 'limp' mode. Sound about right?

I appreciate your time. Oh, how can I tell if it's an OX66? model number on the motor is 6GA150TXRB.

[Ken]

Tony,
If your motor is carbed and it has set up for more than a month w/o being run, then the high speed jets may be clogged up with gum/varnish.
Remove the jets and squirt a carb cleaner like Berryman's Chemtool into the orifices to flush out. If this does not help, then a carb teardown, cleaning, and kit install is probably in order.
Good luck [img]smile.gif[/img] ,
Ken K

[Ken]

Tony,
The warning horn is under the console and is activated when either the remote oil tank is low or an overheat condition occurs. Also, there should be some kind of indication of alarm on your gauges, depending on type of gauges.
When an overheat condition occurs, two things happen - the warning horn goes off and the motor goes into rpm reduction mode. When this happens, the motor will shake violently because the ignition control is cutting back on the spark, and the motor is missing badly.
From what you have described, I don't think your motor is going into rpm reduction. Most likely, a carb problem.
Good luck [img]smile.gif[/img] ,
Ken K

[Parker Boy]

Thanks Ken.

The motor did sit in water for probably about 2 months.(maybe 2.5 months). I originally didn't think, in terms of not running the engine, that wasn't a long time. Then again, I know little about outboards(but, I'm learning ).

I have to agree that it's not an overheat(after reading this thread). Normally for the oil, the days will blink(dash has 3 levels of oil display, full/half/low). Low, the warning buzzer comes on. Happened once.

I will try Berryman's Chemtool.

Thanks again.

[Ken]

Yeah, Tony, carbed motors are famous for clogging up if allowed to sit for any length of time w/o being run. I try to run mine at least once every two weeks in the off season - preferably once a week. If that is not practical, then you need to follow the owners manual for off season storage.
Get youself a Yamaha service manual. It will show you where those carb jets are. The manual will pay for itself. Go to www.yamahapubs.com to order online.
Good luck [img]smile.gif[/img] ,
Ken K

[Parker Boy]

60 bucks for the service manual and I'm ordering it today. Soon it'll be closer to my house and I won't have to worry about sitting anymore. I'll check back in and let you know how I made out.

Thanks for all the help.
Tony

[Parker Boy]

Any chance this is a result of a blown head gasket?

[jb123]

are you hoping for one?? you would have poor running if it would, rusty plugs, etc..

[Parker Boy]

Not hoping for one. Just trying list possibilities for a plan of attack. Saturday, I'll scrub down, put on rubber gloves cause I'm 'going in' ... [img]smile.gif[/img] .. hope to have resolution by end of the day ...

[Ken]

Tony,
I would not at this point suspect a blown head gasket - not ruling it out either. A compression check would answer the question.
Do your carb cleanup and see what difference that makes. Hopefully, your Yammie will be running fine after that.
Ken K [img]smile.gif[/img]

[Parker Boy]

Thanks.

After reading some replies, I think I have a good **** plan. Would love to be on the water by end of the weekend, weather is great right now in the NE. Striper time.