Never have any major issues with this motor. Pulling the kids on the tube this weekend and it just shut off like you turned off the key. Put it in Neutral, it fired right back up and off we went, working our way back to the lake house, running fine and shut off again. Used TM to get us back, ended up messing with it at the dock and was able to hit the button on the throttle and idle it up and get it started. Shut it off and cranked it up a few times and it seemed to be alright. Let it sit overnight and fired up like normal this evening, so we went back out and again it cut off. Was able to idle it up and is ran fine for about 10 minutes and it cut off again. Now, it will start on elevated throttle, but it will shut off as soon as you bring it back to neutral. It feels like it isn’t running on all cylinders at lower throttle speeds until you give it a little more, then it seems to catch until I go back to neutral again and it shuts off. I pulled a line off the fuel pump and it seems to be pumping, but not a lot. Not sure how much pressure it needs. Anybody have a clue? Seems fuel related since it will fire up under high idle.
Part of what you describe indicates bad LP fuel pump(s). Replace all with new is the fix. The V6 OX66 run on 6 cylinders in neutral and “drop” 2 cylinders when put in fwd up to around 1800rpm, then on all 6. Not sure I understand the “elevated throttle” symptom. Not a Yamaha mechanic by any means but have owned and maintained 4 of these for over 20 yrs.
By elevated throttle, I am referring to pushing the button on the side of the control lever that allows you to idle up the motor without putting in gear.
LEE , I KNOW THESE YAMIS ARE SENSITIVE TO FUEL PRESSURE AND DEPEND ON THE PRE-FILTERS BEING CLEAN , I HAD A SIMILAR CONDITION AND HAD TO HAVE FUEL CHAMBER , FILTERS , AND HIGH PRESSURE PUMP CLEANED , NO MORE PROBS AFTER CLEANING , HOPE THIS HELPS …
START WITH A SIMPLE DROP CYLINDER TEST.
WITH THE MOTOR IDLING, PREFERABLY IN GEAR, ON THE TRAILER, BACKED INTO THE WATER, SO YOU CAN APPLY LOAD, UNPLUG 1 INJECTOR AT A TIME, AND SEE HOW THE MOTOR RESPONDS.
IF THE MOTOR IS FIRING EQUALLY ON ALL 6 CYLINDERS, YOU SHOULD NOTICE A SMALL STUMBLE EVERYTIME YOU UNPLUG AND REPLUG AN INJECTOR.
IF IT IS NOT RUNNING ON ALL CYLINDERS, WHEN YOU UNPLUG THE DEAD CYLINDER, NOTHING WILL HAPPEN, AND WHEN YOU UNPLUG A HEALTHY CYLINDER, THE MOTOR MAY SHUT OFF, OR STUMBLE VERY AGGRESSIVELY.
THE OX66 DOES NOT DROP CYLINDERS WHEN SHIFTED INTO GEAR.
THE HPDI MOTOR DROPPED 2 CYLINDERS IN NEUTRAL, AND PICKED THEM BACK UP AS SOON AS THE MOTOR WAS SHIFTED INTO GEAR.
Chris, As of right now, the motor will not crank unless it is throddled up in neutral, once running on high idle, it will shut off when I bring the throttle down to neutral to put is in gear. When throttled up in neutral, is is running a little rough.
okay, then just try the process however you can make it run.
you want the motor to stay running at its lowest possible rpm.
if thats 1000 rpms, then so be it, its not gonna hurt anything, its just harder to “feel” the difference at higher rpms
Ok, thanks all for the input. I’m going to replace the lift pumps just because the motor is 20 years old and that’s never been done, and replace the filters and then get it running and try the injector test. I’m off of work starting Thursday so I will take it to the old boat landing in back of the neighborhood that no one uses anymore and try it. I will be back with results. Thanks again!!
Hanckel usually has lift pumps in stock. Had 2 stolen off my boat before the 4th a couple years ago & got them from them before.
21 Contender
That sucks, I can’t stand a thief!!! I was able to get out there today and mess with it a little. It fired right up as it normally does and after about a minute or so of idling normal, it started to sputter and finally shut off. That’s leading me to believe it’s possibly fuel pump related. Going to start by replacing the two lift pumps and see what it does. If that doesn’t do it, will look at replacing the hp pump that I believe is located in the vapor box. When it died, I pumped the ball and it was fairly full but it wouldn’t crank back up.
Have you changed the vst filter?? If you are going through all this trouble do that & the one on the port side of the motor in the canister housing.
21 Contender
I believe the vst filter is attached to the bottom of the hp fuel pump inside the VST box unless I am looking at it wrong. Figured I would change it if I got to that point of going into the box.
Have you changed the vst filter?? If you are going through all this trouble do that & the one on the port side of the motor in the canister housing.
21 Contender
I believe the vst filter is attached to the bottom of the hp fuel pump inside the VST box unless I am looking at it wrong. Figured I would change it if I got to that point of going into the box.
Ok, so while still waiting for a few more parts, I decided it wouldn’t hurt to hook a portable tank with fresh gas to rule out bad gas even though I couldn’t see anything wrong with the gas coming out the filter cup. I dumped the filter cup again and pulled the drain plug on the VST and caught some in a small glass to check it and sure enough, it had a little water in it. I drained it all the way, pumped the bulb a few times to force gas through and flush it out . I then got a quart jar and a hose and filled the jar up pumping the bulb and pushing gas out the VST drain. Let it sit while a drank a beer and it was clear, no water. Put everything back together, filled it full of fuel and fired it up. It ran rough for a few seconds and started purring. Ran fine for about 30 minutes. Shut it down and an hour later hit the key and it fired up like it always has. I think it just built up a little water in the vst over time and it finally was too much combined to pulling the tube allowed the water to run through. going to have a friend put in with me tomorrow and put it to the test on the river and see what happens. He can pull me back if I got excited for nothing, but I thing this was it.
Still going to replace both LP Fuel pumps and the VST fuel pump filter because they are all original and pushing 21 years old. Should I be fine running some Lucas injector cleaner in the fuel? Anything else I should change while changing everything? I know I should probably switch to non ethanol fuel but I use the boat so much and keep it topped off with fuel when I park it. Keeping fingers crossed, hope this does it.
a bottle of HEET works way better than lucas for removing water from fuel
Proline 201WA
Aloha 24ft pontoon (LooneyToon)
Old Town stern with 7.5 johnson
I was thinking Lucas for cleaning the injectors. I don’t see any signs of water in the fuel, but will dump a bottle of heet in it as a precaution. I think the water in the vAT was a build up over time.
