Rodbolt and Ray: This photo above is of the VST filter on my '98 Yamaha 250hp OB. I believe it's never been cleaned after at least 500 hours of use, probably more. You can see at the bottom of the filter where I pushed away the dirt with my finger. The "whiter" part if the filter element underneath the dirt.My engine started acting up last year in which it would hesitate or drop RPM's for a very short instant, after hitting a boat wake or wave, then resume just fine. Some days each and every wake or large wave would show this hesitation, and at speed, would make you lunge forward in the boat. This began after my first large load of Ethanol laden fuel.Anyway, as an FYI, I found that those small Phillips screws on the VST tank are a beast to get out. I was beginning to strip a few and was real nervous through the process. I ended up having to remove the tank off the engine and bring it to my work bench to get those screws out. There was no way I could do it while the tank was still on the engine. Funny thing was that these screws were Not corroded at all, just in there tight.Also, it seems the gasket (the thin long one) stretched a bit so I will need to replace it.I am leaning on cleaning the filter with soap and water and air drying it well.Any advice you have would be very welcome.Regards,John
At this point,replacing would probably be better than cleaning. Rodbolt has a lot more experience with them and may have a different idea, but I haven't had good luck cleaning when they were as dirty as that one looks.
I have same engines, same year etc., and want to do same service on VST but service man. does not give me a very good step by step layout. Can I ask where you started, I would guess you drained the gas and started taking apart, are you also changing the little final screen (or filter) on top and then just refill with gas, or do you just start and the lower pressure pumps will refill, all questions not sure about. Any help would be great. Thanks
Red Reg: First I got the manual, that will help somewhat. Then I just looked at the whole assembly to understand what goes where. There are 3 bolts that hold the VST to the block. They are hard to get to, but you can do it with some patience. Once these come out, the VST kinda just hangs there. I tried to get all the little philips screws off at that point, but a few got stuck, so I had to disconnect all the hoses and a couple of wires to take the tank to my bench. With some luck, I got all the screws out. The lower part of the VST tank just drops off. The filter is at the bottom and twists off. I will probably take Ray's advice and buy a new one so I start fresh. As for refilling the tank, I assume that if you just pump the bulb and crank the engine that the fuel and oil will mix properly and the tank will fill that way. Perhaps it may be better to add some premix to the whole thing beforehand ?? That's a good question for Ray and Rodbolt.John
Thank you, that helps, so is it your understanding that the only thing that needs to be serviced in the VST is really just the changing of the "pressure pump filter. I see in the VST/Pressure Regulator diagram there is another small filter and o-ring on top of the VST in the pressure regulator, have you looked at that, or is that also in you service plans?
RedRad: After I read your post last night i decided to get to that little filter you refer to. After 5 minutes, I got to it and noticed that it was basically clean. It is not as fine a mesh as the VST Pump filter.John
Thanks Ray for that info. John give us an update when you put it all together and test run it. My engines are doing the same thing you describe in your first posting. I see you are also in CT, I am sure I am getting the same problems from this new fuel. I have heard things like the engines need to run hotter, with hotter plugs etc to handle the water that the Ethanol absorbs...just what I hear not sure which plugs would be hotter than what yamaha specs say to use. Sounds like that VST filter will be the thing that will need the most attention from this new fuel?
Thank YOU for this post! Changing the filter on the bottom of the fuel pump inside the VST solved my problem with a 2000 250 hp Yamaha. We had the same problem with surging, especially when hitting a wave. Thanks again.
Hey thanks John. I am also from CT Portland but my boat is in Old Saybrook. You describe the exact same problems I am experiancing. Returning home from a blackfishing trip satuday every time I came down into a wave the rpm's went from 3500 to 500 and then right back to 3500. This is what your boat was doing right. If you don't mind me asking what was the cost of the repair. This is something well within my technical range so I guess I'll give it a try.