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2004 Yamaha 25 4 stroke losing power

rock_fishrock_fish Posts: 11,711 AG
Remote control on a J16, topped out at 24 with a 9.9x11 prop, no tach

Long story short: in March i had the boat in for not making power and to fix a bearing and they found the timing was off. 3 months later I get it back and still no power. It felt like it wasn't getting over 2k rpm. Took it back to the shop and they found the carb was leaking and rebuilt it. Shop owner said it was making perfect compression, too. 1000 bucks later and it ran good for 30 minutes and loses power again, this time not getting much more than 19 mph. All things being equal.

I do not feel good about the shop i went to, and before taking it to another shop and spending more, does anyone have any insight on what could be the culprit? I'm mechanically inclined so I can do some things short of a rebuild

Replies

  • GotseaGotsea Posts: 610 Officer
    I would say check the timing and spark plugs, make sure all 2 cylinders or working properly, that you have good ignition spark 
  • FletchFletch Merritt Island, FLPosts: 2,455 Moderator
    Not sure if that model had it or not but from my little experience with Yammie 4 strokes, it could be fuel related. I know on some of the fuel injected models there was a little filter (vapor sep maybe?) that would cause problems if it got clogged. Injectors could be affected as well. Your carb version may not have that concern though.

    You could also have a coil breaking down. They can get cracks inside that aren't visible to the eye. Run more or less normal when cold then start doing weird things as they heat up and expand.
    "Ninety percent I'll spend on good times, women and Irish whiskey. The other ten percent, I'll probably waste..."
    -- Tug McGraw on getting a raise

    Get Down Fishing Charters - Port Canaveral, Florida
  • rock_fishrock_fish Posts: 11,711 AG
    Gotsea said:
    I would say check the timing and spark plugs, make sure all 2 cylinders or working properly, that you have good ignition spark 
    Timing should be good as it was just fixed. Or I paid to have it fix. I will check the spark
  • rock_fishrock_fish Posts: 11,711 AG
    edited June 29 #5
    Fletch said:
    Not sure if that model had it or not but from my little experience with Yammie 4 strokes, it could be fuel related. I know on some of the fuel injected models there was a little filter (vapor sep maybe?) that would cause problems if it got clogged. Injectors could be affected as well. Your carb version may not have that concern though.

    You could also have a coil breaking down. They can get cracks inside that aren't visible to the eye. Run more or less normal when cold then start doing weird things as they heat up and expand.
    I dont think it has the vapor separator. If it does I am not sure what it would look like. It has an inline fuel filter that then runs to the fuel pump and then to the carb. Not much else on the line.

    I have the coil part # 65w-85570-00-0 that looks like this



    The plug wires dont seem to come off and it is one entire unit, a bit different than other coils. Not sure how to bench test that, but i suppose putting the probes in the boot and to a common ground?

    Edit: If the numbers I found online are correct, and I tested it correctly, the ohms on the primary are perfect, but the ohms on the secondary coil are 14-15k, whereas the sheet I found says 4.1K. And I checked what I believe is the pulser coil and it reads perfect on ohms, too.


  • hhfishermanhhfisherman Posts: 152 Deckhand
    Before you wasting more money or troubleshooting in the wrong direction. Started with the basic. Check the compression. Make sure it's has good even compression. And then looking at the fuel system. Is your engine started with power and then suddenly or gradually lose power? If that's the case, you are most likely to have fuel problem. It could be a dirty fuel, a bad fuel bulb, or a dirty water separator.
    Ethanol fuel tend to gum up and clogged the fuel line. You can run off a separate gas can to see if the problem still exist and report back to us.
  • rock_fishrock_fish Posts: 11,711 AG
    edited June 30 #7
    As stated in the OP, the compression was perfect according to the mechanic. 

    I always use non ethanol fuel from a plastic 6 gallon tank and fresh gas was used during tbe check ride. There is no water separator. The bulb has not been ruled out yet, however.
  • GotseaGotsea Posts: 610 Officer
    rock_fish said:
    Gotsea said:
    I would say check the timing and spark plugs, make sure all 2 cylinders or working properly, that you have good ignition spark 
    Timing should be good as it was just fixed. Or I paid to have it fix. I will check the spark
    If you did not checked it yourself or saw how and if they di it, I'll make sure myself, you
     weren't that happy with his work 
  • rock_fishrock_fish Posts: 11,711 AG
    edited June 30 #9
    Gotsea said:
    rock_fish said:
    Gotsea said:
    I would say check the timing and spark plugs, make sure all 2 cylinders or working properly, that you have good ignition spark 
    Timing should be good as it was just fixed. Or I paid to have it fix. I will check the spark
    If you did not checked it yourself or saw how and if they di it, I'll make sure myself, you
     weren't that happy with his work 
    Indeed true. The problem being the plug hole is smaller than the rental compression tester and adapters they come with. I would have to buy one and probably will do sooner than later.
  • rock_fishrock_fish Posts: 11,711 AG
    Update:

    I figured out how to take the plug boots off- they just unscrew, who knew?

    Anyway, I rechecked the secondary coil and it is reading 4.6k, so it is within range.
  • gogittumgogittum SW New MexicoPosts: 396 Deckhand
    Is there a Yamaha owners forum you can get on ??  My V-Strom motorcycle quit cold on me last fall and I had fits with it - spent the whole winter chasing a series of inter-related problems thru the thing.  The people - esp. the Australians - on the Strom Trooper forum were a great help in steering me thru it all.
  • rock_fishrock_fish Posts: 11,711 AG
    gogittum said:
    Is there a Yamaha owners forum you can get on ??  My V-Strom motorcycle quit cold on me last fall and I had fits with it - spent the whole winter chasing a series of inter-related problems thru the thing.  The people - esp. the Australians - on the Strom Trooper forum were a great help in steering me thru it all.
    I have a post going on one as we speak. Some good info so far from both sites.
  • FletchFletch Merritt Island, FLPosts: 2,455 Moderator
    A bad vent on the fuel tank could cause a restriction in fuel flow also. Most modern tanks have the vent built into the fuel cap. Loosen or remove the cap to test. Don't forget to test that coil again when its hot. Even then it may read perfect when you test. I had one do this on an old Johnson OceanRunner I owned in the past. Absolute devil to troubleshoot. 
    "Ninety percent I'll spend on good times, women and Irish whiskey. The other ten percent, I'll probably waste..."
    -- Tug McGraw on getting a raise

    Get Down Fishing Charters - Port Canaveral, Florida
  • rock_fishrock_fish Posts: 11,711 AG
    edited July 1 #14
    Fletch said:
    A bad vent on the fuel tank could cause a restriction in fuel flow also. Most modern tanks have the vent built into the fuel cap. Loosen or remove the cap to test. Don't forget to test that coil again when its hot. Even then it may read perfect when you test. I had one do this on an old Johnson OceanRunner I owned in the past. Absolute devil to troubleshoot. 
    Will do this today. Last night I replaced the spark plugs because they're cheap and why not, and put on a new fuel filter. Changing the primer ball and line today with a friends to see if that affects it as well. I'll be sure to bring my multimeter with me and check the vent. Will the temp change affect what ohms it "should" read?
  • FletchFletch Merritt Island, FLPosts: 2,455 Moderator
    I would talk to a trusted mechanic about the coil and testing cold vs hot. I just remember my mechanic going through multiple rounds of testing before finally just replacing the coil altogether. It was fine, more or less, when cold. After it got hot, it would fail sporadically. He was never able to "catch it" with a hot test when it was failing, I'm just throwing stuff out to give you some general ideas. I agree with the others. If your compression checks out, you've either got a fuel problem or a fire problem.

    As others have already stated, you can potentially eliminate a lot of the fuel issues by running on a separate, portable tank with good vent, line, primer bulb and clean non-ethanol fuel. This would quickly tell you if you have an engine problem or a boat problem. The other thing you might be able to do is bypass the wiring harness from your console controls to your engine. For the evinrudes I still take care of, my mechanic gave me a keyswitch with a very short harness on it. One of the first things I do when troubleshooting potential electrical problems is to disconnect the remote harness on the top of the engine and plug in the keyswitch. If everything behaves as it should, I instantly know I have a problem with the wiring harness and/or keyswitch in the boat. Same theory for fuel when running off a good, clean portable tank.

    Isolate the engine from the boat...
    "Ninety percent I'll spend on good times, women and Irish whiskey. The other ten percent, I'll probably waste..."
    -- Tug McGraw on getting a raise

    Get Down Fishing Charters - Port Canaveral, Florida
  • rock_fishrock_fish Posts: 11,711 AG
    Good thing about the J16 is it uses a portable tank. We'll see tonight
  • lemaymiamilemaymiami Posts: 3,795 Captain
    That advice to start with a known good tank and fuel line when you've got motor troubles that aren't obvious is one of the first things a pro will do... If your troubles go away entirely with a different tank of fuel and different fuel line - it's not your motor it's your boat.. Go to a different tank and your problems remain - it's your motor.  Saves a lot of time if it's not your motor and you at least know where the problem should be...

    "Aren't boats fun?"
    Tight Lines
    Bob LeMay
    (954) 435-5666
  • rock_fishrock_fish Posts: 11,711 AG
    A different tank, line, and ball didn't make a difference. After about an hour it dropped power, even worse this time around. I checked the coil and it read within limits.


  • GotseaGotsea Posts: 610 Officer
    You have a component, injector, coil, sensor,  or fuel pump that is giving up as it gets hot, if you have a way it will be interesting to see if there are any fault codes, even better have a computer hooked up as you run it and see what\ code shows up as it is acting up, 
  • rock_fishrock_fish Posts: 11,711 AG
    Gotsea said:
    You have a component, injector, coil, sensor,  or fuel pump that is giving up as it gets hot, if you have a way it will be interesting to see if there are any fault codes, even better have a computer hooked up as you run it and see what\ code shows up as it is acting up, 
    I'm not sure, but I don't know if it has a computer on it.

    I might just have to find a different/better mechanic. A Yamaha specialist
  • Tony RomaTony Roma Posts: 791 Officer
    3 months and 1,000$ and the problem isn’t fixed? Please post the name of the shop so all other forum members can avoid your nightmare. Buy the new coil pack and wire setup ,if it doesn’t fix the issue you will at least have a backup when it does crap out. 
  • rock_fishrock_fish Posts: 11,711 AG
    I picked up a new coil to try, but the plug wires coming off the coil are about twice as long as the original ones. Does this matter, or should I trim them to length? Trimming them would be easy to do as the plug put just screws into the wire, theres no receiving threads in this design.
  • GotseaGotsea Posts: 610 Officer
    It does not matter 
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