OX66 LP Fuel Pumps

[fishinAK1]

Ok. With everyone’s help, I’m getting this narrowed down.

the primer bulb gets firm w low pressure fuel pumps attached. BUT when I loosen the bolts, the bulb goes soft and won’t firm back up after pumping and pumping. BUT I don’t see any external leaks.

is this normal? With pumps loose, where is gas going?

btw 1 yr old oem pumps.

2005 200hp OX66 saltwater series II

 

[seasick]

Loosen what bolts?

 

[fishinAK1]

Sorry. Loosen the 2 bolts that hold each pump to the block.

 

[seasick]

The pumps have multiple sections. Some bolts hold the two sections together and other bolts hold that assembly tight to the block.Those bolts if I remember also squeeze the sections together so Make sure the bolts that don't hold the assembly to the block are tight. Pumps can suffer tears/leaks in the internal diaphragms. If that happens, you may see gas leaking out of the back. There are check valves that can go bad but when they do, you wont see any leaks. You can have an internal leaky diaphram that affects pump pressure but also doesn't leak out the rear.
Note also that the pumps are connected in series so if one is bad, if affects the whole set ( 2 or 3 pumps).
What exactly are you trying to diagnose?

Those pumps wear out and depending on the model year and when if ever the pumps were replaced, they may need replacing. Older lp pumps used a different material for the diaphragms that didn't hold up as long as the newer diaphragms.
On the edge of the pump assembly you should be able to see a small plastic tab that is part of the diaphragm. You may see either a black or clear plastic tab. Now for the kicker; I don't remember 100% what the newer parts are, black or clear but if I had to guess, I would guess that the older ones were black.

 

[fishinAK1]

Seasick, you are a wealth of information and I sincerely appreciate you taking the time to help. Gosh, I wish you were my neighbor!
Well, I guess it’s good to know the pumps can go bad AND NOT see gas leak out the back.
These are 1 year old OEM pumps, but I guess they could still be bad already.

but seems like that would starve the fuel system, not flood it.

 

[fishinAK1]

I’m trying to diagnose a loss of WOT RPMS (from 5500 to 4700) and increased fuel consumption ( from 12 gph to 17gph)

-clean VST and filter (spotless)
-cleaned O2 sensor & housing (lots of carbon & oil)
-cleaned and recalibrated injectors (they were clean but all flooding)
-new Tstats and PCV
-new plugs (all very black especially 1&2)
-new head gaskets (last yr)
-compression 120ish in all 6

gonna check fuel pressure this afternoon..,

 

[family affair]

FWIW, the new design is black on the 3.1.
I've chased issues similar to your experience more than once on a 3.1, never conclusively determined the culprit, but ultimately fixed the issue. Here are my suggestions if sea sick doesn't nail it for you:

• Decarb heavy shock treatment
• Replace the O2 sensor

On the 3.1 there is an O2 sensor that can be had on the aftermarket from an auto parts story for $21. You will have to splice it in. I've ran 2 of these sensors on the 3.1 for over 10 years without issue. You will need to see if the 200 uses the same sensor.
Good luck.

 

[seasick]

Seasick, you are a wealth of information and I sincerely appreciate you taking the time to help. Gosh, I wish you were my neighbor!
Well, I guess it’s good to know the pumps can go bad AND NOT see gas leak out the back.
These are 1 year old OEM pumps, but I guess they could still be bad already.

but seems like that would starve the fuel system, not flood it.

Yes, it would starve the system. That is why I first mentioned that I didn't think it was lp pumps.
Did you happen to smell and wipe the old plugs when you took them out? My nose doesn't work very well ( no, not Corona, it hasn't for years) but you might be able to tell if the wetness is excess gas or excess oil. Keep in mind though that if there is a spark issue (and that is a possibility) the cylinders may not fire and that leaves a lot of mixture in the cylinder. Just one misfiring cylinder could explain the loss of revs. With an ohm meter you can test each plug wire and boot ( did you check the boots to make sure they are screwed in all the way?
Again while thinking over your problem, at first I would think the VST screen is plugged but that will cause surging. Your symptom is that the revs just top out early and stay there. Is this issue new this season perhaps after winter storage or wet storage? Sorry for all these points, I am just thinking out loud.

 

[fishinAK1]

-I didn’t smell them. I will tho.
-VST filter seemed very clean (as has been the usual)
-this fist occurred end of last summer. After it first occurred, we used the boat 2 more times on very short 20 runs. Same
-last week I installed the cleaned recalibrated injectors and cleaned the O2 sensor, housing, & tube. Took it out again. Same thing. Except this time, it also alarmed 30 seconds after being above 4000 rpms. No limp mode. I quickly backed off throttle, and shut down. Restarted seconds later. ...no alarm. I slowly idled back to ramp.
-I just bought new plug boots. First one I pulled took awhile to get an ohm reading. Then after some scratching got it to read .5 (in spec).
-I have the boots, may as well replace em all. Cut wire 1/8” and screw in new? Should I add dielectric grease to screw-in end?

 

[seasick]

I don't have my manual handy and am not sure if the readings are correct. The boot itself needs to be checked and I think that should be a lot higher resistance.
No grease, the boot should be snug enough.

The alarm is something I wouldn't have expected. There aren't too many things that will cause an alarm. As a mater of fact, I think there are only two;overheat and low oil level in the main tank on the motor. That condition will cause the motor to go into limp mode. Oh, there is a possible third alarm but I don't think your motor has it. That's the water in gas alarm. If you have it, there would be a wire connected to the bottom of the motor mounted fuel filter. In addition, I think the water alarm won't silence until the water condition is cleared and the ignition is cycled off and on.
So the alarm may be an overheat indication. That can be a bad sign if it is due to an exhaust leak due to a bad head gasket or other leak from the exhaust system
Did you see a lot of white smoke?
It may be time to get a pro involved
Trying to be optimistic, it is possible that you got something sucked up against the water inlets like a plastic bag. That happens fairly often. The water flow gets stopped, the overheat alarm sounds, you throttle down and maybe shut off the motor to see what is going on and while you do that the bags falls off. Let's hope!

 

[seasick]

Currious, you said the VST filter was clean/spotless. How did you determine that? I ask because the screen can get fouled with a very fine light film and still look clean. The technique I use is to remove the filter and look into the hole that attaches the filter to the pump and see if I can see my fingers on the other side of the screen. If you can, the screen is not clogged.

 

[family affair]

Currious, you said the VST filter was clean/spotless. How did you determine that? I ask because the screen can get fouled with a very fine light film and still look clean. The technique I use is to remove the filter and look into the hole that attaches the filter to the pump and see if I can see my fingers on the other side of the screen. If you can, the screen is not clogged.

Why would you suspect a clogged vst? It sounds like the engine is running so rich it can't burn all the fuel. 12 to 17 gph. When the O2 sensor gets fouled or is damaged, the engine defaults to rich fuel condition to prevent running lean and causing damage. My 225 couldn't hit max rpm, used excessive fuel, and fouled plugs till I changed out the O2 sensor. The sensor actually tested similar to the new one, just a little slower to react. I never had an alarm though.

 

[fishinAK1]

Ya. VST was very clean. Can’t say for sure I could see my fingers but suspect I could.

no sure about alarm. Hoping it’s was just odd fluke w O2 running rich. Weird that it never alarmed this winter the couple times it was used after the problems began.

only thing I did between then and now was reinstall the recalibrated injectors and clean O2.

btw I replaced head gaskets last spring, as preventative maintenance.

Thank you all! This is the best crew ever!

 

[fishinAK1]

Ok. today's update.
I replaced the plug boots.
I bought a fuel pressure tester. Fuel pressure seemed to be right about 34 psi. That's with the key on, idle, and up to 3500 RPMs (that is as high as I was comfy running in a bucket)
Outboard fired right up. idled between 500 and 600 RPMs. This seems a little lower than I remember and maybe felt like it was idling a little rougher than pre-problems.
I brought the neutral throttle up to 3500 RPMs. Fuel pressure still steady at about 34 psi. Ran fine (still in neutral in the bucket) for about 3 minutes. Then it seemed like it began surging (between around 3000 and 3400). During these small surges, the fuel pressure stayed around 34 psi. After 4-5 minutes I shut 'er down. I hate running in the bucket... But no alarms.

Afterward, I finger checked the temp of each cylinder. All seemed about a similar temp. I wouldn't say overly hot, but warm to the touch. I also pulled the spark plugs and peaked at them again. Honestly, they looked better than the other day. in general, they didn't seem as black and not wettish. no gas smell. Perhaps better spark to new boots....?

Thoughts...
Manual says fuel pressure should be 35.6 psi. Considering my cheapo pressure gage and the fact that it didn't bounce around, I am going to consider this within margin of error. What do you think?

To me, this still leads me to think its a failed O2 sensor. ...Rough idle, surging after warm-up.

Whatch you all think? Again, Thanks so much for all the help. and I will be sure to share results and findings in hopes of helping others that stubble across this.
have a nice night!

 

[family affair]

Running in a bucket in neutral will require much less fuel volume than under load. To really determine fuel pressure issues, the engine will need to be loaded. That said, I doubt you have a fuel pressure issue if your flow rate is abnormally high compared to where it normally should be.
NTK 21006 is the alternative sensor on a 3.1 ox66. You can read all about it over on THT.
Also, the odds of having all your plug boots with issues are almost impossible. Does the 200 ox66 have some cylinders with lower compression like the 225 and 250's? That might explain the different plug appearance or it could simply be slight normal irregularities with injectors.

 

[seasick]

The SX models do have two cylinders with a little lower compression. The difference is not a lot.
The fuel rail pressure should stay steady regardless of load assuming as you note that there is sufficient flow to satisfy the needs of the motor at a specific load.
Two things about the latest post that I don't fully understand. To my knowledge, there are no O2 audible alarms or any alarms for that matter other than overheat or low oil in main tank

The surging mentioned would normally be an indication of fuel supply issues but if that were the case, I would expect corresponding fluctuations in the fuel rail pressure.
Perhaps there is a problem with the throttle position sensor. That can be checked with an ohm meter.

The earlier statement that the voltage produced by the O2 sensor when heated with a torch may indicate a problem or something was wrong with the method of testing.

What does it mean to say " Then it seemed like it began surging (between around 3000 and 3400) "? It either surged or it didn't.

If the motor idled between 500 and 600 it will idle rough and may also sputter. and spit. That is not an issue related to the other problems.

Yes as noted, it is unlikely that all boots would go bad at the same time, but it also only takes one bad one or plug wire or weak coil to cause a loss of top end revs.
If I can make a suggestion it would be for you to do more diagnostic testing using the procedures in the manual before changing every part that might be suspect. If you test and find a suspect part because of the test results, than after replacing that part, the test should pass. If your first approach is to replace a part, one, you may never know if that was the problem and two; you will go broke

The changing of head gaskets is also new info. Was that the cylinder head gasket or the cylinder head COVER gasket? What was the reason?

 

[Harpoon]

If you've done all those maintenance items, I'd add LP pumps to the list. They are cheap and should be considered a service-item.
What's odd here is your fuel burn.... you've not changed props? You aren't taking on water weight ?

 

[fishinAK1]

Sorry, the surging was very slight and kinda hard to identify for 100% sure while the cowling was off and running in bucket.

I changed both the head gasket and cylinder head gaskets last spring. Simply because there seemed to be a littleweeping around the outer edges. It was completely preventative. And the outboard ran fine on multiple long trips after that, before the current symptoms occurred.

ha ha testing before buying new parts is exactly what I’m trying to do! I tested the fuel pressure and tried the o2 flame test. Most of the electrical test listed in the manual just don’t make sense to me. They identify a tool I don’t have and/or the spec it should be but no indication on how-to.

I did order LP pumps. As they are cheap enuf and seem to be a common problem. ...even tho mine only a year old. 1 more question in those. When they are loose from the block (but still held together w their screws) should the the primer bulb get firm? Mine doesn’t.

i agree one component I havenot tested and read about problems w is the Throttle Position Sensor.
Could anyone tell me a proper test (preferably from bench) theft for the TPS?

Thank you!
btw. I am only going to post on THIS thread. The other one will be put to bed.

 

[fishinAK1]

1 more thing. NO changed props or significant additional weight.
Additional fuel burn began right after the first surge, shortly after getting in step. Before that surge 12 gph after that surge 17 gph. And loss of top end rpms.

 

[seasick]

The TPS is a potentiometer that changes resistance as it is rotated. There may be 3 wires or 2, I get confused between my Ymis and Mercs. ( Again Yami SX manual is not here with me.)
I don't even remember the resistance range but whatever the range, pick two leads and connect the ohmmeter. Rotate the shaft or level of the TPS and watch the readings. The ohms should increase or decrease (depending on direction of rotation and wires picked if there are 3), The changes should be smooth and uniform with no spots where you read a very low or very high resistance)
The TPS can often be tested while still on the motor as long as you can disconnect the connector to allow the test meter to be connected to the sensor AND you can make the throttle move though its range. That can be done by someone at the helm..No ignition, just dead motor.

When you changed the head gaskets did you follow the proper tightening sequence and the proper torque steps?