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Not familiar with the Suzukis, but you mentioned it is fuel injected, is it a four stroke or two stroke?
The air bubble in the filter is perfectly normal and expected. You mention the fuel looks clean, but are you sure you are not looking at water in the filter bowl? How old is the fuel? I would pull off that filter bowl and check for water.
Does your buddy have the owner’s manual for the engine handy? If so, I would read up on what ever warning or safety RPM limiting features the engine might have. Perhaps it is overheating and is being slowed down by the computer….In any event, this faltering above 2000RPM may be an actual warning from the computer about a particular problem.
You mentioned that pumping the fuel bulb does not help the issue, so is doesn’t seem like a fuel delivery issue, but you never know. I would suggest trying another tank, but I’m guessing there are no other suzukis around to borrow a tank from…Again, please be careful if this is a two stroke, surely don’t want him substituting a fuel tank with straight fuel when his two stroke might require a fuel/oil mix… So, if another tank is not available, I would pull the supply line off the filter and direct it into a glass jar. Now connect the fuel line and pump the primer bulb, he should see a steady stream of fuel coming out of the hose. If all appears normal, I would reconnect the inlet fuel line and disconnect the fuel line leading to the injectors and repeat this process…I’m not sure how easy it is to remove this line on a fuel injected engine though. Certainly do not attempt to remove some fitting that he is unfamiliar with, don’t want him to break anything. If all appears to be OK, go ahead and reconnect all the fuel lines. Now, your friend should locate the electric high pressure fuel pump, shouldn’t be too hard to find. With all fuel lines reconnected, your friend should have someone turn the key switch to the “on” position while he listens and has a few fingers on the high pressure pump..He should hear/feel the electric pump running for a few seconds when the key switch is turned “on”. Please advise being very careful, the assistant may accidentally turn the key to start, make sure his hands are clear of the flywheel and other moving parts…
Again, I should have led with the most basic steps….By all means, pull the plugs, perhaps one is failing at higher RPMs, hopefully he can find some new ones in the area he is at. Have a look at all the electrical connections on the engine, make sure nothing is loose or damaged. And, of course, start with the battery connections. Loose/corroded connections with drive the computer crazy. He should check battery voltage with the engine running to ensure the battery/alternator is working properly. He may want to check each cell with a hydrometer, or have the batter load tested.
Sorry, I don’t know more about this engine, but my best advice is to treat is as a simple outboard and make all the basic checks you would on that engine. Again, he should be very careful not to squirt fuel all over the place or create sparks doing a spark check. Probably a great idea to keep a fire extinguisher handy, this engine develops plenty of fuel pressure from the high pressure pump…
Hope this is a case of always check the simple stuff first…DI don’t know which model you have exactly so I picked a random 25 EFI. They do things a little different than Yamaha so my info is not applicable about a filter inside the VST. It looks like they might have a separate HP filter, number 3 in the diagram. I still think the best way to test is with a fuel pressure gauge. There is usually a Shraeder valve someplace; but not always. Are you sure you don’t have some water in the fuel? The rapid decline in run quality that you describe is not usually consistent with a high pressure filter.
Long live American manufacturing!
I don’t know which model you have exactly so I picked a random 25 EFI. They do things a little different than Yamaha so my info is not applicable about a filter inside the VST. It looks like they might have a separate HP filter, number 3 in the diagram. I still think the best way to test is with a fuel pressure gauge. There is usually a Shraeder valve someplace; but not always. Are you sure you don’t have some water in the fuel? The rapid decline in run quality that you describe is not usually consistent with a high pressure filter.
OK, well Bill’s diagram is helpful. Looks like there are a couple of different fuel filters in that system. And yes, just because the liquid appears clear in the filter does not mean it isn’t water. I would definitely drain it out and check…True, you would think there would be some separation of fuel/water in there, but perhaps not if it is all water.
It kinda sounds like the high pressure pump is crapping out slowly, but perhaps there is some other fuel delivery issue. Can you remove the plastic covers that shield the electric fuel pump? If so, I would try turning the key switch to “on” while holding fingers on the electric pump to see if it cycles on for a few seconds every time the key switch is turned on…
Look for the shrader valve like Bill says, must be there somewhere. You can probably “rent” the pressure gage from a local auto parts store to monitor the fuel pressure. But, beware, just cuz the fuel pressure might be low does not automatically condemn the electric pump….So, please don’t buy a new pump based soley on a low fuel pressure reading.To follow up on this problem (in case 50 years from now someone is restoring one of these), my friend took it to a dealer, and the problem was, as a couple of you suggested, the high pressure fuel filter. The dealer changed both filters, and briefly told him how to find and change the high pressure filter. A couple big parts have to come off, including the long intake manifold that stretched across the starboard side of the powerhead before you can even see the part. He was told that filters are about the only problem they ever see with that model.
They charged him for 3/4 hour of labor.
Thanks again for all the suggestions – I probably could have fixed it last week on our fishing trip if I had metric tools along, but then maybe I’d have dropped parts in the lake, and it’s hard enough sometimes to find parts dropped on my workshop floor!…..and I would have been learning on someone else’s nearly new motor.
Dave
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