# 2002 OX66 250 bogging down



## WhyMe (Apr 21, 2013)

I finally put the boat in yesterday and push away from the dock and everything looking good until I started to open the throttle open. The engine seems like it's starving for fuel ( got no more than 7.5 knots) got back to the dock and tied up. The engine is running good I pressed in the button to get the RPM's up ( got them up to 3000-3900 with no problem with the engine) . I pushed off again and ended up with the same result no more than 7-9 knots. Back to the dock and loaded up and back home. Please keep in mind I just bought this boat/engine just a few weeks ago. I have not replaced nor fixed anything on this 2002 Yamaha ox66 250. It looks like I might need to replace every filter on this boat since I don't know squat about what the previous owner had or has not done. 
I know it's in my best interest to do this, or is it the filters?
Thx in advance. 
Whyme


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## DAWGONIT (Jan 16, 2009)

concur with your diagnosis. spend some time going over everything.
how about the age &/or quality of fuel?
lower unit oil &/or previous damage.

as you indicated, idle vs. load are two different creatures.

good luck.


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## lastcast (Oct 12, 2007)

Might want to try to run it off a 5 gal external tank first. If nothing else it'll half split your problem. But filters, separator and fuel lines is a good guess.


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## kanaka (Oct 3, 2007)

Agree with above post. Time to break out the wallet and change/replace everything even if it looks fine, don't assume. Don't forget impeller kit.
I'm guessing it ran fine when you did your trial run before purchase? For the fuel check, get some out of the gas line and give it the ole sniff test.


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## WhyMe (Apr 21, 2013)

When testing the boat it ran great. Cruising at 31mph at 3900 RPM's and top end around 48 mph at 5400 RPM's with 3 adults and 125 gallons of fuel, but no gear. Should I check the 
O2 Sensor? I heard that might cause problems. 
Whyme


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## lastcast (Oct 12, 2007)

Run on external tank first. You could swap everything out first if you want.


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## O-SEA-D (Jun 28, 2016)

Remember that clogged fuel filters can also limit lubricant from getting to the cylinders as well. No good.


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## WhyMe (Apr 21, 2013)

Well, just a few hours ago I ordered a Vst fuel kit ...one step at an time...does anyone know how many gas filters are on one of these engines....next step will be the plastic tube gas filter sitting on the side of the engine then 10 micron water/fuel separater down below. 
Whyme


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## user6993 (Feb 15, 2009)

After you have try everything with the fuel. Check your oil filter on the remote oil tank. If it becomes restricted and slowly adds oil to the engine oil tank you could get a RPM restriction decreasing your RPM while running. Next time you are running and get this low speed condition pull your engine cover and check your oil tank level. Check that your warning buzzer for low oil conditions is working. Best of luck.


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## divefins (Jul 6, 2016)

I had this exact problem in an OX 225. Turn out to be the anti-siphon ball was bad. With no load would run fine, under load the squeeze ball would collapse due to suction.
Check the other fuel components also.


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## Sequoiha (Sep 28, 2007)

To much info to write. If you message me I’ll give you my phone number and we can talk.


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## DreamWeaver21 (Oct 3, 2007)

WhyMe said:


> Should I check the
> O2 Sensor? I heard that might cause problems.
> Whyme


Leave the O2 sensor alone right now. They can cause issues but not likely the behavior you are describing. An O2 sensor issue would be more like a surging issue or dropping RPM while running and not likely something as drastic as what you describe.

Running on a separate fuel source is a good suggestion however if it was me and I bought a 15 year old motor that I didn't know the history of, I would be doing a full service to the fuel system anyhow. For me working on an an OX66 that would mean:

-Cleaning the VST tank. Some replace the VST filter but it is just a screen and expensive and a 2 dollar can of carb cleaner does wonders. You may want to have a new special gasket ready to put it back together. They can be reused but not all the time.

-Replacing all 3 low pressure fuel pumps.

-Replacing the paper element in the onboard filter.

-Replacing the external spin on fuel water separator (assuming there is one).

-Replacing the fuel lines and bulb going to the motor. I am assuming it is 15 years old too? I've gone to using Shields 368 A1-15 hose because I believe it to be the best.

-Possibly pulling the fuel pickup to check and make sure it isn't clogged and checking the barb and making sure it is a straight through barb. Not a fan of the anti siphon ones.

You issue could (probably) be related to one of these things but if it were me even if I did them one at a time to find out which one fixes the issue, I would still do them all to know where I am at with the fuel system.

If that doesn't solve it, dive deeper into it but know that you didn't waste any time or money doing the above things IMO.


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## WhyMe (Apr 21, 2013)

Thx to all that has committed. I'm slowly working on the problem. Given I have little time to dive into this all at once this is what I've done so far.
Ordered VST fuel kit
Ordered cup filter
Did the smell test of the fuel. Smelled and looked very clean. 
Checked and dumped out fuel the bowl in the Raco water/fuel separater (no water at all).
I will be ordering a new Raco filter here soon along with new hose and primer bulb.
Here is a pic of what the Raco filter and hoses look like.
One thing I've noticed is the Zip ties on the hoses not metal clamps. To me that's a problem as well. 
Whyme


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## WhyMe (Apr 21, 2013)

Here is a closer look of the zip ties on the fuel hoses. 
Whyme


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## Jason (Oct 2, 2007)

Fuel lines that have a liner gets deteriorated over time and will collapse, so like others have said---replace all the fuel lines.


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## kanaka (Oct 3, 2007)

WhyMe said:


> Here is a closer look of the zip ties on the fuel hoses.
> Whyme


Makes you want to slap someone on the side of the head sometimes.

Talk to Kenny about the issues.


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## WhyMe (Apr 21, 2013)

Dreamweaver21....I looked at my hoses on my Mako 223 and I do have the same hose as your talking about. My boat mechanic told me to use them and that's been over a year ago and no problems. I will use them on this Yamaha engine. 
Whyme


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## DreamWeaver21 (Oct 3, 2007)

Is that yellow handle valve near the fuel water separator involved in the fuel system? If so why? That needs to go if it is.

Also, when you run new lines secure them and the primer bulb so they are not swinging around in a sea wearing your hoses out and stressing your zip ties (which I am sure you will replace).


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## X-Shark (Oct 3, 2007)

> Is that yellow handle valve near the fuel water separator involved in the fuel system? If so why?


It's a fuel Shut Off valve.....It's used when changing the filter.

You will note why I recommend the Stainless Mount for the Racor...As you can see in this pix the corrosion of the alum powdercated one in the pix.

Also Move the squeeze ball. Have it between the tank and the filter....Not between the filter and the motor.

They are designed more to push.....Not suck. The only time with a 4 stroke that you will use the ball is when you do a filter change. It will fill the filter 5 times faster placing it between tank and filter and not wear your hand out.

That Blue hose that Harbor View has is a good replacement for your Gray hose.

Use a Sharpie and date your filter when you change them.


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## pappastratos2 (Aug 8, 2016)

what solved the issue?


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## WhyMe (Apr 21, 2013)

Sorry for the delay, but what solved my problem was the the two wires coming from the water thermostat both A and B Bank were being pinched by the engine cowling when put back on. Also one wire the white one was wired up all Messed up.That sent the engine into alarm mode making the engine go into Limp Mode. Thus saving the engine. I re wired the wires and zipped tied them better.
Whyme


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## WhyMe (Apr 21, 2013)

Another pix.
Whyme


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## WhyMe (Apr 21, 2013)

I'm still learning the ins and outs of this ox66 along with working 59-64 hours a week so time is very short for me to work on her. LOL 
Whyme


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## pappastratos2 (Aug 8, 2016)

Thanks for lettings us know what solved the issue. I wish everyone would do that, helps the rest of us to diagnose our motor issues!!


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