I have read about surging problems on this site and other sites, but have yet to find a solution to my problem. Last year I noticed it surge/bog (by about 200-400 RPMS in about 20 second intervals, although not necessarily regular). My mechanic cleaned the very gunked-up O2 filter and it worked fine. He also replaced the oil pump, since the old pump was putting way too much oil out (and likely contributing to the gunking). It then ran fine all of Nov '04 and up until July this year.<br /><br />In mid-July, it started doing the same "bogging" in RPMS, then suddenly worked fine. I then managed to get a tank of bad gas (about 2 gallons of water in it), so the mechanic pumped out the water, changed the fuel-water seperator, checked the pump filters and "blew out" the lines.<br /><br />I then took the boat out on Labor Day and it ran fine for about 30 minutes in the 3600-4000RPM range. For the last couple of minutes, though, I opned her up to 5200 and the bogging began again. Yesterday, I took her out again and the bogging was worse than ever. While she ran very well up to around 2000 (maybe even 2500), she bogged pretty severly above 3000 (300-500 RPM fluctuations constantly, not just every 20 seconds but a near continuos up and down).<br /><br />Reading other posts related to other motors, I see the following culprits appear over and over:<br /><br />(1) Bad O2 sensor (but mine was cleaned last Fall and has about 80 hours since then...much of it trolling, though);<br /><br />(2) Clogged VST filter (not sure what that is);<br /><br />(3) Bad fuel pump (can I simply squeeze the rubber ball while its bogging to see if the motor stops bogging, thereby indicating that I do have a bad pump?);<br /><br />(4) Clogged injectors (can I simply put standard injector cleaner into the gas?).<br /><br />My mechanic doubts the problem is electrical since it runs fine at low speeds and Yammie electrical systems don't often go bad.<br /><br />Thanks for any input you can offer!
