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Thread: yamaha t50 jet runs smooth but loss of power

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    Member akprideinvegas's Avatar
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    Default yamaha t50 jet runs smooth but loss of power

    Hey gents, quick question. First off i have not pulled the jet apart to check for shim or missing key.

    So I have a yamaha 2010 T50 with a jet and 192 hours. It runs smooth yet has no power to get on step with a load. It seemed to get progressively worse. I could not tell if it was only when i was loaded or when i was unloaded too. When looking at the jet when runnning it blows a large mess of water but not smoothly like it used to. I dont know what would cause this and the shop just recommended pulling the lower unit apart and checking everything. I will pull it apart thursday when i have time in hopes of being good for friday.

    On a second note, has anybody else had any issues with fuel pumps? the dealer replaced my fuel pump under warranty at 150ish hours (last summer) and I think it might be going out again. I had slight hesitation and motor die when running this weekend but never happened again. (that was a common occurance when the fuel pump went) and im getting a light nocking sound on the motor.

    Thanks
    NRA life Member JVJ

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    Member jkb's Avatar
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    Maybe I'm misunderstanding the issue. I would think your impeller/sleeve are worn after 192 hours. You also could have rocks in your jet discharge.
    Life is not a journey to the grave with the intention of arriving safely in a pretty well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming-----WOW-----what a ride!
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    Member akprideinvegas's Avatar
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    Rocks in the jet discharge could be a factor and will confirm/deny that. Im hoping for something simple!! But I replaced the entire foot, sleeve, impeller combination last fall before I put it away and it should be singing. I beat up the previous combo pretty well and it still ran better than it is currently.
    NRA life Member JVJ

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    Member akprideinvegas's Avatar
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    No rocks jammed but sleeve is worn more than expected. Nothing that looks too bad but will replace sleeve and put back together and hope for the best. Are there any websited to get jet unit and yamaha parts from to save cash or is in town the best option? thanks again
    NRA life Member JVJ

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    Moderator stid2677's Avatar
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    Quote Originally Posted by akprideinvegas View Post
    No rocks jammed but sleeve is worn more than expected. Nothing that looks too bad but will replace sleeve and put back together and hope for the best. Are there any websited to get jet unit and yamaha parts from to save cash or is in town the best option? thanks again
    Make sure to shim it correctly.
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    Member Dirtofak's Avatar
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    Professional Marine on Potter.
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    Member akprideinvegas's Avatar
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    thanks for the shop reccomendation. I spoke to another shop in town and they said everything looked good the way it was setup. I pulled the foot apart and only minor wear on impeller/sleeve combo. There is nothing blocking the water exhaust or anything else. They did say to pull the coolant lines and blow air through to ensure nothing is blocking in the line where it enters the cooler to cool the fuel. Ill try it and I will put back together and hope for the best when i run it on friday. Appreciate the help
    NRA life Member JVJ

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    Moderator stid2677's Avatar
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    I don't mean to insult,, but make sure the jet foot is put on correctly. I have seen a few installed backwards and the results are similar to what you are having.
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    Member MRFISH's Avatar
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    Quote Originally Posted by stid2677 View Post
    Make sure to shim it correctly.
    Ditto to what Stid said. If you haven't already adjusted the shims, that's a regular maintenance kind of thing as the impeller and sleeve wear down.
    "Fishing relaxes me. It's like yoga, except I still get to kill something." --Ron Swanson

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    Member akprideinvegas's Avatar
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    Im tracking on how to install the lower unit and yes it is shimmed appropriately. thanks guys
    NRA life Member JVJ

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    I can think of one or two things that aren't common but I have had happen. The first is that your driveshaft key, or the flat spot on the shaft, are wore and under full load they slip.....

    Second one is that your reverse cup is out of adjust ment (and the bushings over time can also wear, allowing it to kick up under load) and it then sprays your clean jet water all over the place instead of straight back and as touch as those lovable jets are, that can take you from zipping to plowing pretty quick. Even more fun when the cup slaps back into reverse while on step.....a heart stopper for sure.

    If it was your sleeve or shimming, you would have cavitation, especially out of the hole, and your motor often sounds like it's missing but it's the revs from the air going through the foot. But, you said your motor sounds smooth.....so I'd say that part of it is fine.

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    Moderator stid2677's Avatar
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    Okay,, I would start with the fuel,, replace it with a fresh source, clean and inspect all fuel filters.

    Check the fuel vent,, a plugged vent will cause fuel starving,, sometimes wasp clog the vents on built ins and failing to open the vent on portable cans.

    Some newer engines have a "limp home mode" that is designed to restricted RPMs when there is a fault.

    Check the plugs..

    Check for restricted air flow.

    Make sure the throttle rigging is fully opening the throttle.

    A compression check would rule out more serious issues.

    Good Luck
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    Member akprideinvegas's Avatar
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    Catch It and Stid, its like you were out front working on the boat with me. This evening I drained the fuel tank and flushed and blew as much of the little debris that was in the tank from 2 years of filling up with 5 gallon jugs. Then I pulled all the fuel lines and blew them out. Tomorrow I will replace fuel filters. I will also refuel from the pump. The more I researched online the more fuel seemed to be an issue. My plugs are looking great and there is nothing prohibiting air intake. The fuel tank breather is operable but I blew it out and cleaned it up anyways.

    The shop I spoke to said my reverse cup looked fine so I have not messed with it but when I get it in the water tomorrow I will make sure that I look behind to make sure it is not slipping up. For some reason how you explained it, I feel like this could be the issue though since I do have water blowing willy nilly at times. That would be great if it was as I can fix on the river.

    The driveshaft key is definitely in place and the impeller is shimmed appropriately (3 washers currently, I had 2)

    I have not done a compression check, however I am bringing a fuel pressure gauge to check pressures while I am driving to see if the motor is starving when Im WOT.

    I don't think I have a large issue and its something minor. I have not had to throw any money at it yet and replacing fuel filters can never hurt. Ill report back. Thanks again.
    NRA life Member JVJ

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    Member akprideinvegas's Avatar
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    Woke up this morning and looked at my reverse cup for a quick moment. When i am at WOT and I push/Pull in on the threaded end (that connects to the foot) I can get it to move in and out nearly 1/2 inch. So I think I might need to replace my control cable. Im sure thats not an acceptable tolerance. It takes pressure to make it happen but it does move.
    NRA life Member JVJ

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    Quote Originally Posted by akprideinvegas View Post
    Woke up this morning and looked at my reverse cup for a quick moment. When i am at WOT and I push/Pull in on the threaded end (that connects to the foot) I can get it to move in and out nearly 1/2 inch. So I think I might need to replace my control cable. Im sure thats not an acceptable tolerance. It takes pressure to make it happen but it does move.

    Closely inspect the pivot bushings and linkage components at the reverse bucket before you condemn the cable, the bushings are a common wear item/s.

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    Agreed 338, the cable itself usually isn't the issue, it can be the screw that holds the cable down on your lower unit, or the tiller arm that allows for some slop. Easiest way to tell is to put it in forward while on the trailer, then try to pull the cup backwards into the neutral or reverse position. If by hand you can get the edge of the cup to be in front of your jet exhaust, you definitely have a problem, then work backwards starting with the bushings as 338 said to get all that wiggle out of there. I find this happens more with after market jet set ups (which I believe you have) than factory set ups. IT doesn't take much to mess with jet performance, that's for sure.

    While Stid outlined the exact right way to go about diagnosing a poor performing motor from the simplest (fuel) to the most painful (compression issues), I have found with jets that I go straight to the lower unit unless I have compelling evidence that the engine itself is the issue. They are way more often the issue than the motor itself. Obviously it could be either or all but for my field work as a biologist in AK for the past ten years, I have worked with more jet motors of different makes, models, ages and levels of disrepair than most. And have never sent one back to town because the head was blown or timing was off or crank was shot, but have swapped out more feet, sleeves, impellers, keys, cups and bearings than I wish to recall.

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    Member akprideinvegas's Avatar
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    The reverse cup was not adjusted correctly and though the gate was opening all the way, it was not locking in position. Quick Fix and im good to go. Thanks again for the experience and tips
    NRA life Member JVJ

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    Excellent!

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    Glad to hear it was a pretty simple fix.

    I would recommend getting a complete set of all the components involving the reverse gate and spare them on board - including a gate. If the hinge pin holes on the gate start to wallow out - REPLACE THE GATE. Otherwise you run the risk of putting oblique pressure on where the hinge pin enters the actual jet bowl housing, which results in you needing to eventually replace the jet bowl. Not cheap. The parts kit won't take up much space and can really get you out of a pickle in the field. The hinge pins and nylon bushings are by far the quickest to wear item. Ensure you put the wavy washer on the port side hinge pin as it helps keep the roller centered in the cam plate on the starboard side.

    I'd also recommend making a copy of the schematic specific to your model of jet unit and keep it with your parts stash - helpful when you are working to reassemble components back in the right order/etc, as well as how to properly adjust your cam plate for proper forward lock/etc.

    http://outboardjets.com/jet-kit-instructions/

    Last resort to solve reverse mechanism issues when in the field is just remove the gate if needed to limp home.

    Final bit of advice - you can save a TON of wear and tear on the hinge pins and nylon bushings by keeping controls in the forward position while trailering so the gate isn't rattling while on the road.

    XL

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    Member dkwarthog's Avatar
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    Glad you got it figured out akpride.

    Maybe I'm just dont know what I am missing, but I have never had a reverse gate on my 35 horse jet and I cant really think any time that I have wished for it.

    Is it that useful to you guys? Will it even keep you from drifting with the bow facing down river? Just curious...because it doesnt look like it would be all that effective. Thanks

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