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Max Online: 36273 @ 01/23/13 02:34 PM
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#11738235 - 07/23/16 02:48 PM Yamaha vmax 150 - fuel problems
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX
Motor has always run fine. Had a lower unit replaced, and while it was in the shop I had the carbs rebuilt and a hot foot installed. It has run like junk ever since. The symptoms are:

1. Will not idle. Idles extremely rough and slow and then putters out.

2. Has become very tough to start, and when I finally get it started there is a huge smoke cloud, then the smoke goes away. Have to have the throttle hammered down to get it to start and run.

3. After idling onto the trailer bunks, I give it throttle and it bogs down and shuts off. At this point after restarting it every time I mash the throttle to push it on trailer it bogs down and dies. Also, at this point, I can't back it off the trailer without the engine bogging down and dying.

4. It used to run at wot at about 5000 rpm. Now, after I get it on plane, max rpm is about 4400, then slowly fades to between 3800 and 4000. If I make a sweeping turn, it briefly goes back up to 4200 rpm then fades back down to 3800 and 4200.



I'd appreciate any and all thoughts.



Edited by CoachCBA (07/23/16 05:05 PM)
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#11739036 - 07/24/16 07:26 AM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 10765
Loc: Littlefield Tx & Lake A. H. US...
Manual fuel pump diaphragms.
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#11739158 - 07/24/16 09:14 AM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX


do you mean these pumps?
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#11739172 - 07/24/16 09:25 AM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX
Or do you mean the bulb between the tank and the motor?
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#11739631 - 07/24/16 03:03 PM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 10765
Loc: Littlefield Tx & Lake A. H. US...
The arrows point to the manual fuel pumps or low pressure fuel pumps. The diaphragms are a known yamaha problem. They rebuilt the carbs on this motor in the picture?
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“The world will not be destroyed by those who do evil, but by those who watch them without doing anything” GOD IS GOOD

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#11739677 - 07/24/16 03:43 PM Re: Yamaha vmax 150 - fuel problems [Re: gary purdy]
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX
Originally Posted By: gary purdy
The arrows point to the manual fuel pumps or low pressure fuel pumps. The diaphragms are a known yamaha problem. They rebuilt the carbs on this motor in the picture?


No, I found this picture online. I'll see if I can change these and see if it helps.
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"One can only get so stupid, then you die." - Pilothawk

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#11742123 - 07/25/16 09:06 PM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
Stump jumper Offline
TFF Celebrity

Registered: 04/19/04
Posts: 7065
Loc: Rockwall
Take it back to the shop that did work. I had carbs on Merc rebuilt once a got some bad needles. Before mechanic replaced them he made me replace all the fuel lines. You could have bad fuel lines flaking on inside. If so you will chase your tail tearing down carbs.

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#11743626 - 07/26/16 05:48 PM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
blackhorse Offline
Outdoorsman

Registered: 05/13/08
Posts: 114
Loc: Morgan, Tx
What year is your engine?

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#11743993 - 07/26/16 09:08 PM Re: Yamaha vmax 150 - fuel problems [Re: blackhorse]
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX
Originally Posted By: blackhorse
What year is your engine?


2006.
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"One can only get so stupid, then you die." - Pilothawk

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#11773959 - 08/12/16 06:02 PM Re: Yamaha vmax 150 - fuel problems [Re: CoachCBA]
CoachCBA Online   content
TFF Celebrity

Registered: 07/10/10
Posts: 6132
Loc: Whitehouse, TX
Update:
Turns out the shop that did the original work did not change the plugs, which were fouled. Service Marine in Emory changed em, synced the carbs and adjusted the idle and it runs like a top now.

Should have gone to Service Marine the first time.
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