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About 3 weeks ago, motor started acting up with the typical VST symptoms, bogging, falling off rpms, etc. I tried my fuel/water sep. first since it was 5 weeks in a figured, while early, could be a contributor. Didn't help..was able to manage about 5 kts with now stuttering...give it anymore and the rpms would spike up and down, occasionally stalling out. Re-starts were no problem..averaged 5 kts. Started with the basics, checked primer bulb to VST tank to see that fuel was filling the tank. Poured fine out the drain as I compressed primer bulb. Bulb would remain firm so ruled out air leak. Paper filter in fuel bowl was dis-colored(last replaced June 2018) so replaced that. Opened up VST, very little debris, bottom filter on medium pressure pump was warped and discolored-replaced with OEm filter and new o-ring. Went back out..symptoms were back in 3-4 minutes. Would start off planning up to about 3500rpm and start to stutter and bog. Checked plugs which were 2 season old OEM NGK's and 4 of 6 were fouled pretty dark. replaced..went out for test run-still the same. Ran on temp tank, fresh 93 gas..symptoms the same. Next up changed out the strainer. Went back out 3-4 minutes of better..symptoms back. I had a brand new OEM medium pressure pump ready to go for this situation so replaced it, replaced the VST filter assembly as well and new oring again..have a couple in the freezer now(these things are ridiculous). Ran the boat for 4-45 minutes-feeling good..seas were not cooperative for full throttle but able to be around 4200-4400 rpm. Practiced stop and starts, gradual acceleration as well as full throttle take off. All good..feeling good...fast forward to yesterday. Switched back to main tank, ran for 30 minutes to an anchoring spot..4 hours later, head out to go top of tank and add ringfree, 5-6 mins in, starts acting up with same symptoms again.
So, next up, I'm going to go back to temp tank and see what happens. I had not had a fuel pressure pump available to test the pressure in VST tank under idle or under load so will do so. Assuming I'm 47-50 psi, assuming that isn't the issue there having added the new pump. I decided to pick up a new primer ball and some new A1 fuel hose as I'm at about 4-5 seasons but have a hard time believing that is a failure point. If symptoms are the same, I had ordered 2 oem low pressure pumps, gaskets, etc and will replace those. If it continues after that, I presume it could be the float needle in the VST tank(which I ordered as well). I have not given up but running out of stops before making it to the myster filters in the block and the 6 mystery filter in the injectors..my understanding is that the mortor would not give any performance if the High Pressure pump was damaged. I have not cleaned/removed the O2 sensor, but again, that's the low-end 1500rpm and under so don't think that's the issue. Throttle position sensor? Don't know...open to other suggestions and advice based upon other's findings...summer is short and the queue at the boatyards is long already so trying to rule out the little things before we get out of my pay grade and experience and comfort. I've seen some issues with folks trying to get the small filter out of injectors and the block with them crumbling or getting stuck-don't want to bite off too much.
Thanks for the feedback.
So, next up, I'm going to go back to temp tank and see what happens. I had not had a fuel pressure pump available to test the pressure in VST tank under idle or under load so will do so. Assuming I'm 47-50 psi, assuming that isn't the issue there having added the new pump. I decided to pick up a new primer ball and some new A1 fuel hose as I'm at about 4-5 seasons but have a hard time believing that is a failure point. If symptoms are the same, I had ordered 2 oem low pressure pumps, gaskets, etc and will replace those. If it continues after that, I presume it could be the float needle in the VST tank(which I ordered as well). I have not given up but running out of stops before making it to the myster filters in the block and the 6 mystery filter in the injectors..my understanding is that the mortor would not give any performance if the High Pressure pump was damaged. I have not cleaned/removed the O2 sensor, but again, that's the low-end 1500rpm and under so don't think that's the issue. Throttle position sensor? Don't know...open to other suggestions and advice based upon other's findings...summer is short and the queue at the boatyards is long already so trying to rule out the little things before we get out of my pay grade and experience and comfort. I've seen some issues with folks trying to get the small filter out of injectors and the block with them crumbling or getting stuck-don't want to bite off too much.
Thanks for the feedback.