1993 Yamaha vx-250 surging

[Krazysun]

Hi, I recently bought this vx-250 and it seemed to run fine on the back of the guys boat sitting on land. However once I installed it on my boat and put it under load, the motor would not climb past 3200 rpm and then would loose all power as if fuel was cut but does not die, it keeps surging up and down in RPMs.

Sometimes it idles smooth and sometimes rough, not consistent.

I have been reading many post on iboats but nothing has helped so far.

I have taken a remote tank and connected directly to the outboard with a primer ball and had a friend pump gas while I slowly added power and I was able to get the motor up to 4500rpm and stay there for a few minutes but as soon as I touch the throttle she died out again.

New filters, new plugs, mechanic inspected fuel pumps and indicated they were all good, ran SeaFoam threw it. I have drained the carb bowls and they all seemed clean.

I hate missing out on summer. Any help would be appreciated. Thanks

 

[ksmith3846]

Re: 1993 Yamaha vx-250 surging

Hi, I recently bought this vx-250 and it seemed to run fine on the back of the guys boat sitting on land. However once I installed it on my boat and put it under load, the motor would not climb past 3200 rpm and then would loose all power as if fuel was cut but does not die, it keeps surging up and down in RPMs.

Sometimes it idles smooth and sometimes rough, not consistent.

I have been reading many post on iboats but nothing has helped so far.

I have taken a remote tank and connected directly to the outboard with a primer ball and had a friend pump gas while I slowly added power and I was able to get the motor up to 4500rpm and stay there for a few minutes but as soon as I touch the throttle she died out again.

New filters, new plugs, mechanic inspected fuel pumps and indicated they were all good, ran SeaFoam threw it. I have drained the carb bowls and they all seemed clean.

I hate missing out on summer. Any help would be appreciated. Thanks

I have the same problem with mine 93 200 txrr no one on here knows what the problem is i just removed my carbs and cleaned them let them soak overnight blew them out replaced all the fuel lines in the motor the only thing that is not new is the fuel pumps i do get some surging around 3200 rpms but still cant figure it out. their have been a lot people with this same problem and someone has figured it out. any help would be greatly appreciated

 

[99yam40]

Re: 1993 Yamaha vx-250 surging

Like always the recommendation is to monitor the fuel pressures/vacuum to see if there is a restriction and that fuel pumps are doing what they are meant to do(in spec)

All a motor needs is good compression on all cylinders, good spark on all cylinders, proper timing at all RPMs, and then it is on to the proper fuel air ratio .
Pressures/vacuum are easy to measure to make sure the supply is good, but seem no one whats to check all of this.

If all is good then you are left with the injectors or carbs depending on the motor or it is sucking air some where causing lean conditions

 

[ksmith3846]

Re: 1993 Yamaha vx-250 surging

how do you minitor the fuel pressures and vacuum what do i need to do that ?

 

[99yam40]

Re: 1993 Yamaha vx-250 surging

this should help
http://forums.iboats.com/showthread.php?t=283363