25 HP Suzuki Problem

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  • outbdnut2

    US Member - 2 Years
    Replies: 1603
    Topics: 83
    #246621

    Hey – I know this isn’t an old motor, but hopefully somebody can help me! I’m on a week long fishing trip in northern Minnesota and my friend’s motor isn’t running right.

    2015 25 HP Suzuki – fuel injected.

    It starts and idles fine, but above 1/4 throttle (6 MPH on a 16 foot aluminum boat) it falters big time and slows down. I’m thinking i’s a fuel delivery issue, but I could be wrong. Pumping the primer bulb does not help and the bulb is firm. The cylindrical plastic fuel filter at the rear of the motor looks clean. There is a small air bubble at the top of the filter. All fuel line connections inside and out look tight and good. When we first head out with a cold motor, it revs to about 2/3 throttle OK, but after about 10 seconds, it’s faltering, big time and he has to back off the throttle. This is the first problem this motor has ever had.

    Is there some problem like this that this model is known for? Maybe fuel pump or is there a fffuel pressure regulator for the injectors?
    Any thoughts will be appreciated
    – Thanks!
    .


    Mumbles

    Canada Member - 2 Years
    Replies: 5122
    Topics: 274
    #246627

    It could be caused by a bad spark plug or another electrical component such as the neutral rev limiter kicking in.

    • This reply was modified 3 days, 5 hours ago by Mumbles.

    RICK EICHRODT

    US Member - 2 Years
    Replies: 228
    Topics: 61
    #246632

    Check the fuel line from tank thru primer bulb to the fuel connector at motor. Take off the connector at motor, remove the hose and see if it is plugged up with deterioration from inside of fuel line causing it to restrict fuel flow. Otherwise, maybe water in fuel?


    fleetwin

    US Member - 2 Years
    Replies: 4030
    Topics: 41
    #246646

    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…D

    • This reply was modified 3 days, 2 hours ago by fleetwin. Reason: addition

    billw

    US Member - 2 Years
    Replies: 1573
    Topics: 46
    #246652

    You need to check the running fuel pressure. I’m not sure exactly what it’s supposed to be but Yamahas are usually in the low 40 psi range, What you’re looking for is for the fuel pressure to drop off big time, as the engine starts to falter. If you can pump the primer, it doesn’t help and the fuel pressure still drops off, you’re probably looking at a VST filter. This is a small but fine filter that protects the high pressure pump inside the vapor separate tank on the engine. Also, though, check for a filter between the low pressure pump and the VST….those are sometimes harder to see until you trace the fuel system out.

    Long live American manufacturing!


    fleetwin

    US Member - 2 Years
    Replies: 4030
    Topics: 41
    #246658

    You need to check the running fuel pressure. I’m not sure exactly what it’s supposed to be but Yamahas are usually in the low 40 psi range, What you’re looking for is for the fuel pressure to drop off big time, as the engine starts to falter. If you can pump the primer, it doesn’t help and the fuel pressure still drops off, you’re probably looking at a VST filter. This is a small but fine filter that protects the high pressure pump inside the vapor separate tank on the engine. Also, though, check for a filter between the low pressure pump and the VST….those are sometimes harder to see until you trace the fuel system out.

    OK, now this sounds like some good advice….


    outbdnut2

    US Member - 2 Years
    Replies: 1603
    Topics: 83
    #246665

    Thanks for all the tips. Spark plugs have already been changed (3 cyl). Yes it’s a 4-stroke. Fished this afternoon and again it trolled fine but had to go slow between fishing spots. On the last leg, returning to cabin at about 5 MPH, it got steadily worse, and would quit under mild throttle increases, but always started right up again, with good cranking so battery is OK. Finally it quit when put in gear, and after a couple of more starts, it would no longer start. Had to get towed. Fuel filter still full, and it’s white semi-clear plastic that you can see into – no water there and fuel looks good at that point. I don’t have any way here of measuring fuel pressure to injectors. After the fuel filter, the fuel goes to a black plastic round thing about 2 inches in diameter and 1/2 inch thick that only has a fuel line in and out and it is mounted vertically at the rearmost part of the engine at the bottom just below the cylinder head. I can’t see if there is any connection to the engine behind it for vacuum, etc., but this maybe the low pressure fuel pump. From there fuel goes to the starboard side of the powerhead, behind intake manifold to a cylindrical black plastic thing with a small diameter rubber line attached to the top that could be a vacuum line or a higher pressure output line of it – maybe this is the high pressure pump? The manifold hides most of it. I can’t see any more of the fuel path and don’t have much along for tools. I’ll look again with that VST filter in mind, but I doubt I can see or identify it. We have two boats here for 4 guys and will limit the dead boat to a couple fishing spots close by that we can go to and from with the electric trolling motor. There is no Suzuki dealer the area.
    Again, thanks for the tips, and if anyone reads this that knows this engine and can offer more insight, it will be appreciated.
    Dave


    billw

    US Member - 2 Years
    Replies: 1573
    Topics: 46
    #246671

    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.

    https://www.boats.net/catalog/suzuki/outboard-by-year/2018/df-25thlw2-beginning-vin-02504f-810001/fuel-pump

    Long live American manufacturing!

    • This reply was modified 2 days, 12 hours ago by billw.

    fleetwin

    US Member - 2 Years
    Replies: 4030
    Topics: 41
    #246680

    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.

    https://www.boats.net/catalog/suzuki/outboard-by-year/2018/df-25thlw2-beginning-vin-02504f-810001/fuel-pump

    • This reply was modified 2 days, 12 hours ago by billw.

    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.

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