ox-66 surging

[Mikviy58]

2001 250 OX-66.
I was running my motors at 4100rpm and for most of the summer they never missed a beat. A few months ago, one of the motors started "surging". It would drop down a few 100 RPM and then run fine again. I cleaned the O2 sensor and everything was OK for a short while. It happened again, only the motor would drop to 2000RPM and sounded like it wasn't running on all cylinders. It would then "Kick in" for a while and run fine, then drop back down again. Drop the motor to idle and it would sometimes stop.

All low pressure fuel pumps and the O2 sensor have been changed. Mechanics on holiday. The fault is constant now, so he should be able to find it when he gets back. I was wondering if anyone would like to hazard a guess as to what is causing the problem?

[99yam40]

Do you know if your buzzer works?

Have you tested it lately?

Could be it is going into RPM reduction but alarm is not sounding, as it limits RPM to 2000 if overheat or low oil

[Mikviy58]

Buzzer works fine. Just changed all the ignition switches, control module and buzzers as the old one fell apart . Oil flow is fine. No overheating.

[Mikviy58]

Thanks for the ideas. I checked the primer bulbs first time I had this problem and they were OK. I do get a fuel smell, but only when I fill up. I plan to change all the fuel lines anyway as they are probably original and 10 years old. I change fuel filters every 3 months. I'm trying to keep this dialogue going so others can learn from my problem. I have a very good mechanic who will fix the motor after the holidays. All the points brought up so far are very useful information. I am pulling the boat back to the house tomorrow for it's winter makeover; All new LED lights, autopilot and new custom switch panel. I have trouble with the fuel management gauge working intermittently, so bought new sensors, harness and gauge at a steal of a price. I'll post up what was wrong when I find the problem with that.

[Mikviy58]

update:

The problem was the VST canister filter. I thought it was cleaned out when the motor was serviced. Apparently not The problem was that the motor would run fine for about 20 minutes, then start acting up. It eventually got bad enough it would do it at the dock. We put the fuel pressure gauge on, and saw it fluctuating wildly. Cleaned the filter, which was blocked, and everything worked fine. I will have the filters replaced with the spring service.

[99yam40]

Thanks for the update, wish all would come back with what problems were found