OK...I'm frustrated and need a little help...Ox 66 problems

[BlackChamp]

So...2 months ago I bought a 2004 Champion with a 250 Yamaha ox 66. Brought it home to Canada. Dealer said it should be a 74 MPH boat. First few runs she would hit 70, then 68, then 67 , then 65 ...oh oh...Now this weekend 63 with this added bonus...Running with the pedal down ( wot) for any more than one minute and it basically shuts down, like it's starving for fuel....it will catch again after I slow right down, and will run all day at 4500 RPM's. PLus after 3/4 throttle , pressing the rest of the way seems to do nothing. After researching here on the board it has all the symptoms of needing low pressure fuel pumps. It really smokes at start up and idles sort of rough. I also saw a post about a fuel pump relay .....not to sure about this though. I pulled the plugs and they are fairly fouled.
I have ordered 3 new pumps from boats.net Does this sound about right to you all?

Thanks for the help

Bill Corrigal


Modified by BlackChamp at 2:35 PM 6/9/2008


Modified by BlackChamp at 2:37 PM 6/9/2008

[DMSOUTH]

I'd also check the fuel pump filter in the VST tank--probably never been cleaned. It's a small round screen on the end of the pump--1/4 turn counter clockwise to get it off. Be careful with the top cover gasket--if you plan to re-use it, make sure it doesn't touch any gas, or it will swell and not fit properly.

[slapshot]

Check the O2 sensor also. That is what mine did when it was gunked up. It ran fine, but lost top end speed and rpm's.

[JUST-IN-TIME]

fuel pumps
clean vst strainer
clean o2
check tps also while u r at it

[STROKEDYAMAHA]

I ran a 3.1 from 97-07 my suggestion instead of cleaning the o2 REPLACE IT and make sure ro replace the gaskets and housing sheild also.

[MNXD9]

Here's a cheap option to replacing the 02 sensor, haven't tried it myself, but I will if the day comes.... http://www.bbcboards.net...90218

[ghind]

You will blow it up very soon if you keep running it that way.

Most probably isn't getting fuel.

Is the primer bulb hard or soft if somebody squeezes it at those speeds?
Have you checked the three fuel pumps for leaks? $100 and 15 minutes to replace all three of them. And due by now as preventative maintenance.

How many hours has it done?

You can measure the o2 sensor in situ, that often quoted link is very old and not the right way to do it. There are 4 wires going in, two are +12 volts for the heater wires, the other two are the sensor outputs. Will go into detail next time.

Start with those two things and we'll help from there.

[BlackChamp]

Well

I have changed all three pumps and checked the VST filter. Put in 2 cans of seafoam and will be trying it out tommorow> WISH ME LUCK!!!

Thanks to all for the help!

[BlackChamp]

ALRIGHT!!!!!! Issue solved...I can run WOT all day ( and watch the fuel guage drop) I got some of the spped back ...now back up to 68. I need to figure out if this really is a 73-74 MPH boat or not.

Thanks to all who helped.

Bill Corrigal

[spider1]

Not really up on Champion boats but with a 250 I would think that it should run in the low 70's. You may need a different prop or prop work.

[EDEERNET]

How much did all those fuel pumps cost you ($100?) Does this really only take 15 mins to do? I have an '04 OX66 and my primer bulb never gets hard, but I've never had any problems with the engine running. It smokes alot when you first start it and the throttle response sucks, but I've never experienced any speed loss. Are these pumps something I should invest in now and replace this winter "just to do it"?

[Justin T - CT]

I have an 03 ox66 225 Just bought the fuel pumps off boats.net cost me $119 for the pumps and the gaskets and shipping. Parts #38 (fuel pump) & #51 (gasket) on the chart they give you. Make sure you get both. Highly reccomend boats.net

Very easy to use and they already shipped it out in less than a day. To bring my boat to the guy to fix was gonna cost me a lot. The installation is easy!

[JUST-IN-TIME]

yep, boats.net is great for the eastcoast guys

we beat their prices but are on the westcoast

[BlackChamp]

JIT...I just sent you an IM.

[55excl]

What is your opinion on the 04 silverado o2 sensor.

[HaulinBass]

What model Champ? If it's a 206, I don't think your going to see 74 unless it's on the interstate. But, there are some fixes for speed on that OX66.

[BlackChamp]

it's a 2004 203 with the tank under the seat



Modified by BlackChamp at 4:03 PM 6/21/2008

[spider1]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlackChamp &raquo;</TD></TR><TR><TD CLASS="quote">it's a 2004 203 with the seat under the tank
</TD></TR></TABLE>
Now that is a boat I would like to see!!! How is the head room???

[ghind]

There is no need to replace the O2 sensor if it tests right.

It is best to test the o2 sensor with the proper harness but you can do it by just sticking your multimeter into the back of the plug where the wires enter it. All you need to do is monitor the output voltage of the o2 sensor. Once the engine is war, at all RPM ranges the o2 sensor should constantly average about 300mv but show lots of voltage swings. So your readings may be 150, 600 220, 700, 220, 400 but all centered around 300mv. It should move quickly. If it is taking a reading and moving quickly it is reading right.

It is still good preventative maintenance to clean it every 100 hours and you should do that but there is no need to toss it away. Also if your o2 sensor tests properly you can find and fix the actual problem (which isn't the o2 sensor) before introducing other changes.

When you remove the o2 sensor, you need a gasket kit handy you can't put it back with a damaged gasket and shouldn't reuse the old one. The bassboat central article on o2 sensor work is VERY old check the date. It is based on very old Yamaha info and is no longer recommended. Don't use a blowtorch on your o2 sensor!

To clean, get a little canister like an old film canister, put some ring free or seafoam in it and put the end of the o2 sensor it. Only allow the mesh bit to be covered, NOT NOT NOT the threads.

When testing, note that 100mv is very lean and 900mv is very rich. 300mv is good.

If your motor runs rich at low RPM, about right at 3000rpm and lean above 4000 you may have a battery voltage problem which can turn into a powerhead replacement problem if you keep running it above 4000rpm that way. Could also be a fouled o2 sensor.

Another good thing, if you know the throttle butterflies are opening right up (max airflow) and the motor is running the correct air/fuel ratio, you are getting full power. Then you can concentrate on other things like prop, jacking plate, nose cone and other setup issues to get your speed cause you know your motor is right.

One plug on the o2 sensor is 12 volts for the heater element, the other is the sensor output. Both are safe to measure with a voltmeter set to 20v to work out which is which if you don't already know. The output goes to a plug at the very back of the motor. The power feed plug can be found in the battery wire connection area. If you are going to put the prongs in the back of the plug, be sure not to create a short.

Greg