# Yamaha OX66 surging



## bonedaddy (Sep 8, 2008)

I have a 2001 Yamaha 250 OX66 Saltwater Series motor model#LX250TXRZ. I recently changed all three low pressure fuel pumps, fuel filter in the clear bowl on motor, fuel water separator, and spark plugs. I have ran it twice since doing this, the first time it ran great, but only ran 8 miles one way and 8 miles back in the bay just testing everything. On Saturday I took it out for the second time and it ran great, idled around Avalon bridge a little and was about to shoot across to 3 mile bridge. When I pushed the throttle it bogged down almost immediately and would surge like it wanted to go but wasn't getting enough fuel. Headed back for the dock and was able to get it up to about 30mph but if I touched the throttle it would bog back down. 

I know that the VST filter is a big issue along with the O2 sensor on these motors but I did check my fuel pressure at the VST tank and it is a steady 35 psi. Also it starts up and idles perfectly. I later found that the fuel hose that goes into the vapor tank from the top low pressure fuel pump was missing a hose clamp and if touched even lightly it would hiss and gas would come out. Is there enough vacuum on that line to cause it to suck air and surge like that? 

Thanks, Kevin


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## B-Rod (Feb 16, 2010)

Sounds like it might be a voltage issue check ur ignition switch voltage while under a load


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## sniperpeeps (Mar 5, 2011)

Had a similar issue with a similar engine. It is sucking air and that's why it's surging. Sometimes even with those clamps in place, fuel injected engines can suck air so I bet without it it's getting a lot of air. I wouldn't run it until you get it fixed because you could do some serious damage.


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## bonedaddy (Sep 8, 2008)

Thanks, I'll check both of these. Unfortunately the only way I have to check it under load is to run it. Hopefully I will be ok as long as I don't continue to run it if the problem is still there. May have to take it somewhere. Thanks for the replies.


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## Hired Hand (Nov 25, 2008)

I had the same thing on my motor. Took it to Kenny and he replaced my knock sensor. Couldn't tell you where it is what it even looks like but it runs like new again. Wasn't a very expensive part and he did it in short order. might want to take it to him.


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## bonedaddy (Sep 8, 2008)

Thanks for all the suggestions. I will repost after determining the problem.


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## bonedaddy (Sep 8, 2008)

*Update to yamaha ox66 surging*



B-Rod said:


> Sounds like it might be a voltage issue check ur ignition switch voltage while under a load


Just wanted to give an update for those who took the time to give me some suggestions such as this voltage issue:thumbsup: I cleaned my O2 sensor, checked all my plugs and installed clamps on fuel line that were missing on top of VST tank ( all on Saturday) Fast forward to Sunday, go to start boat which had been on battery maintainer since last trip.....wouldn't turn over. The starter was trying to spin but not enough juice.

I then start checking wiring and other possible electrical issues as B-Rod suggested. I first disconnected both batteries and took the Blue Sea add a battery switch with relay out of equation. I then hooked up motor to one battery (my house battery because the starting batt. was dead) It fired up but after shutting down and trying to restart it wouldn't even turn the starter. Go to remove battery from boat and when lifting it up was overwhelmed with the smell of battery acid! It was in a battery box thank god but I do believe that to be my problem, regardless a definite problem that needed fixing. I am never buying a cheap battery again though I believe my VSR was bad not allowing the proper charge to both batteries explaining why I had to start my boat with switch in parellell last trip.

I installed a G24 800CCA 1000 MCA Interstate battery last night and hooked up to motor, starts first time like it always used to. New battery so it showed about 2/3 full charge before hooking up, after starting was reading a solid 14.0 volts on gauge while at idle. I will try to test in water tommorow evening to verify all repairs and will follow up again. I am hoping the cleaning of the O2 sensor will resolve my loss of RPM at WOT, 5000 last trip used to get between 5400-5500 (the sensor was very dirty) Also noticed that my primer bulb actually gets hard now when priming after about 3 pumps. Maybe sucking air at the fuel line where hose clamp was missing? Thanks to all who responded


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