OX66 Problem

[dunepray]

OX66 problem

Thanks Rodbolt,
Haven't done a leak-down test yet. Will do. Compression was good. Thinking about your A/F mix theory makes sense. I would think leaking from the back of a LPFP would allow more fuel back into the cylinders at the wrong time. I don't know if this is occurring with mine. I'll let you know, and Thanks for the help.

Dune

[rodbolt17]

not only does a blown diaphragm make it run poorly.
it can damage pistons and crankshafts.

[dunepray]

OX66 Problem

Rodbolt,
So far, none of the LPFP's have leaked from the rear (block side). And the bladder was not blown out, just the seal. Talked to a local mechanic and he said he had never seen them do that. Anyway, I asked him about torque on the bolts, to which he said that they should only be snubbed. No mention in Yamaha manual. I had been putting what manual chart says for the M6 bolt (5.8 ft/lb). So maybe the torque was deforming the cover plate. They don't leak when bolts are in, and when loosening they start to leak. I put three new LPFPs on her yesterday, along with HPFP filter (which really didn't need changing in my opinion). Took her out and she seemed to run fine. Let her warm up well, then slowly took her through the paces to 4k. I didn't push her. Was cruising along for a good ten minutes when she backed down again. I brought her to a stop, turned the motor off, then re-started and did it all again with same results. The mechanic I spoke with told me that once the motor was warmed up and idling properly, there should be no spark on the #5 plug. If there was spark, there is a problem with one of the sensors. I put a spark tester on there and had spark. So my question would be if the mechanic was right about the two cylinders shut down at warm idle on this motor? The manual doesn't say anything that I can find. I've seen pro and con about that on websites. The ECU must be working off it's basic mapping. I've got another local mechanic coming over in the next couple of days to look at her.

Dune

[dunepray]

FINAL UPDATE AGAIN,
Got the LPFPs straightened out. AND, took her down to a fellow who is ace's in my book on OX66 and Yamaha in general. He went through all the notes on the work I've done and within ten minutes of working on her, found out the stator was bad. As the heat range in the motor increased the stator broke down. Couldn't get it to idle right and once in awhile it would idle right and run up RPMs ok, but just as soon as the motor got hot she broke down. New stator coming and will be together by the weekend. I am one happy camper.

Dune



Hey Guys,
I'm not a tech, so bear with me and forgive me if I don't explain things well. Rod, I was at a point when the motor was cold and not idling right (very low, and stalling). The starboard bank of cylinders had NO SPARK. The tech grabbed a meter and test harness (that I don't have) and she was putting out 225V on one side and 65V on the other. Clearly bad stator. Got it on and she's running right. Initial start idles over 1k and as it warms it settles to 700-800 RPMs. Still sputters a bit (probably due to running on 4 cylinders), but runs right through the throttle ranges well. 4900-5000 max, which I think is a little low. I was not personally on the sea trial, however, the tech said she ran well with the exception of the RPM range, which he states should be approximately 5500 at WOT. I will take her out tomorrow providing the weather doesn't turn sour and report what, if anything, I find different than reported.

The prop is an M-17, so may have to go down a bit to get the RPMs in the mid 5k range. I don't know much about props, so I will again have to educate myself. Boat is a Caravelle 230WA with dry weight at 3650. Motor approx. 500. Fuel at 130 gallons is another 900. Equip and bodies minimum 500. Load minimum 5500. I am wondering if the tech who set the boat up may have been working off the original Yamaha spec's and not what's recommended today. Anyone who is knowledgeable on the props, I would appreciate your imput.

Dune

[99yam40]

Sounds like some one tested voltages into and out while problem showed up.

Not sure the whole stater was a problem ( depends on what he calls stater and replaces)
just the charge coil or pulser coil could have been a problem

As long as it works and you are happy

[rodbolt17]

I have so many posts on CCS it aint funny.
OX66 3.1L motors use CCS.
sparks all 6 at cranking.
drops #5 between about 600 and about 2000 RPM.
drops #2 between about 850 and 2000 RPM
Vx motors do NOT use CCS.

stator output voltage is to simple and basic to monitor.

I think you are going to own a spare stator.

if stator output voltage was failing it will affect at least 3 cyl on the same bank.

[99yam40]

stator output voltage is to simple and basic to monitor.

Sorry, I guess I over stepped my knowledge again on this CCS thingy

I get so confused after a few cold ones
and some times even before

[islandman1]

FINAL UPDATE AGAIN,
Got the LPFPs straightened out. AND, took her down to a fellow who is ace's in my book on OX66 and Yamaha in general. He went through all the notes on the work I've done and within ten minutes of working on her, found out the stator was bad. As the heat range in the motor increased the stator broke down. Couldn't get it to idle right and once in awhile it would idle right and run up RPMs ok, but just as soon as the motor got hot she broke down. New stator coming and will be together by the weekend. I am one happy camper.

Dune

Your issues have almost exactly mirrored mine.After $1200 in repairs I changed mechanics.The new one found the stator bad in mine also. I will pick it up this weekend and lake test.

[madharchod]

talking about fuel ARRGH we have the worst fuel in the world down under ,its terrible even the engine starts giving problem on the first day of operation wanna get hold of the drongo who invented ethanol ,he has basically f88d the fuel every-way possible

[rodbolt17]

you will most likely own a spare stator.
Ethanol belongs in my tumbler with ice.

buy decent ethanol and no mixer is required.

[dunepray]

LAST UPDATE
The saga is over. Thank Christ on a raft!!! I took her out this morning and she ran flawlessly. I did trade props from the 17-M to a 15-M and she runs max RPM at 5500. Hole shot is great. I don't even need to use trim tabs. The only differences I can tell are that planing rev's are a bit higher 3500 v. 4000 and WOT speed is 37 v. 39 mph. I do think the motor runs easier with the new prop. Stator definitely the major problem. Thanks guys for all the input. Learned a lot.

Tight Lines,
Dune