250 0x - The Hull Truth

vinnyf · 03-08-2007, 10:56 AM

my question please. my yami 250 ox is a 2001 last year it started doing this.as i was running after it hit a few waves the motor would throttle down (like hitting the brakes ) and than just pick right back up.my mechanic thinks this is an ethanol problem and will be adding star tron to my gas.also since i only get out once a week he suggest adding stabil to my gas on a regular basis,and this will clear up the problem.i just talked to the owner of a yamaha dealership and he said the dead give away was when i said it starts after a couple of bounces in rough water,he said this means the o2 sensor needs to be cleaned not specifically changed but cleaned.what do you guys think?

Edited by vinnyf 3/7/2007 3:10 PM

A1 Outboard · 03-08-2007, 08:11 PM

Vinny,

I kinda doubt the O2 sensor is the culprit in this case, more likely debris inside the vapor tank that bounced up and restricts the electric fuel pump inlet screen. This can easily be confirmed by running the motor with the fuel pressure gauge installed on the VST and watching for fluctuations when the motor starts acting up. Also a vacuum gauge on the inlet side of the fuel pumps and a length of clear line can indicate if the boat's fuel system has intermittent restrictions or air bubbles in the line from leaks.

For O2 info and cleaning, read this article: http://www.boatsetup.com/O2sensor.pdf

Mr. Bee

A1 Outboard · 03-09-2007, 09:32 PM

Do not use startron! I have seen the chemical analysis and it is nothing but kerosene (snake oil). The gauges are the answer. Yamaha suggests using Ring Free at all times. Many times a shock treatment with Ring free will also help. The vapor separator filter should be inspected and replaced if necessary on a yearly basis. Be sure to install a new o-ring gasket on top of the VST. A Yamaha 10 micron water separating fuel filter is a must to catch the junk the alcohol in the gas is dissolving in the fuel system. The operation of the O2 sensor can be checked with a test harness and DVOM if you have access to them. Mr. J

John_Madison CT · 03-11-2007, 10:51 AM

I had the same exact ( I mean EXACT) thing happen to me with my 250 Ox66. It was a clogged VST filter. Replaced that, and the engine was good as new.

vinnyf · 03-11-2007, 05:47 PM

thanks guys

vinnyf · 03-11-2007, 05:49 PM

i always use ring free and was told by my mechanic to start using startron also.