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  1. #1

    A Big Thank You! And Another Question?

    Just wanted to say thanks! I am a first time ski owner just boguht a used '96 slt 780 that was very clean and worked great first time on the water. I had a MFD not working and had no idea on how to keep up maintenance etc..everyone has been a great help! I have fixed the MFD, blown fuse, fixed the bilge pump, also fuse, cleaned the auto bilge line/hoses and filter screen that was clooged up due to dirt dobbers on screen from ski being stored a year prior to me buying it. I feel much more confident and fimiliar with the ski and how to take care of it..members of this site helped me identify probs and gave exact steps to fix them, supplied me with manual and one even sent me the 1/4 amp fuse for the mfd in the mail and did not even know me. The fuse is only found in my area at radio shacks and they were all out.

    This experience has been great. Those who've helped have been a blessing! This site is one of a kind, just as I had read on many posts prior to joining and asking my first question. No one here seems to have the big head and be cocky or rude to newcomers to the sport.

    Now for two more questions! Can anyone tell me can the sealed drive shaft coupler be lubricated without tearing ski apart?..I have been told that a needle nozzle on a gease gun can be pushed in the rubber o-ring to lubricate this. I do not know how long it's been since this was done and just wanted to perform a little PM before it's too late, but do not want to tear anyhting up in the process. MFD says ski has 293.7 hours, is this alot for this age of ski. It was owned by a boat mechanic, one owner, and bought ski and trailer for $550.00, friend of a friend, guy had money and did not need ski any longer. I though it was a great deal!

    Be honest with me, does that sound like a good deal or not. I was worried that MFD could have been tampered with or reset etc. like odometers on a car.

    Again, Thanks a million, If I can help anyone with my now, very limited knowledge feel free to holler!


  2. #2
    Rocky_Road's Avatar
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    "MFD says ski has 293.7 hours, is this alot for this age of ski?"

    Not at all...might even be a little low, if this ski was used in the South, where the riding season can seem to never end!

    Glad to see that you got the proper fuse, and didn't compromise the safety factor.

    Have fun...and help keep the Polaris dream alive!

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    MFD hours are not the important thing. What is important is the mechanical condition of the parts - engine and the rest of the machine.

    In fact, these MFD are known to sometimes reset the engine hour reading to zero, often when a battery is changed, or it sits without a battery for some time.

    Do you know if the engine has been worked on, specifically if the 'top end' has been freshened (new piston rings, cylinder hone or re-bore, maybe new pistons)?

    In any case, checking and monitoring cylinder compression will help you know how the engine is doing internally. You don't need to check it after every ride, but every so often, check the compression.

    You will get to know what the expected readings are, and when one or more cylinders starts to show lower compression numbers, you will know to start paying more attention to it, as something is changing inside the motor.

    Each time you check compression, have a good look at the business end of the spark plugs. Get to know what 'normal' looks like on your plugs. If any of the spark plugs starts to look different, or different from the others, then investigate some more.

    Also monitor the peak full power RPM on the MFD (in smooth water). If the top RPM starts to decline, then the engine may be losing power, and further investigation is warranted.

    And of course, visual inspection of everything else is important. Check hoses for rubbing, wear and soft spots, clamps for tightness. Check wires for rubbing and wear spots.

    Keep the hull interior clean, so you can better see what condition things are in.

    Check the jet pump area. Look for loose bolts, worn bushings, debris, etc. Look in the intake grate, not just at the back of the pump.

    Check the steering. It should be smooth operating with little play or slop. Lube the steering rod where it slides through the bushing at the jet pump. Lube the steering at the front end too.

    Keep the battery clean, and check the connections for looseness or corrosion. Keep track of how old the battery is. Make sure the protective plastic cover over the battery is in place. When you replace the battery, buy a good quality AGM type battery.

    Before you start the machine, check the battery voltage shown on the MFD. Make note of what 'normal' is for MFD voltage before starting. When the reported voltage starts to show less than usual (0.1 or 0.2 volts less), then you need to investigate. The battery may be getting weak, or the charging system may not be not working properly.

    Ride safely, know the rules, and learn as much as you can about boating safety.

    Post a few pictures of your ride, and enjoy being out on the water!

  4. #4
    Thanks again,

    Ill be printing this out for my paperwork/maintenance records and do all the items you've suggested.

    Have not been inside engine yet...Carbs etc. are very celan...No rebuild or anything according to previous owner.. He worked at a marine service place and had tech's keep up the maintenance. Compression was checked just before I bought ski, according to the owner anyway. I did not ask what compression was, figuring I need to get that done myself or with someone I trust so I have a good starting point to keep up with the progress as you stated above.

    Put ten hours or so on ski the first weekend I bought it. Top speed that weekend seemed to be around 50 mph, full of fuel and I weigh about 170 lbs. this speed was figured by comparing with my brother in law's old boat I was riding beside..Not sure how accurate that is. Plugs/wires and air filter appear to be brand new. No problems so far and trying to keep it that way with preventive maintenance.

    Can you tell me about the sealed drive shaft coupler. I've been told to use a needle type injector to lube the coupler through the thick rubber o-ring on the rear side (side closest to rear of ski), can this be done, or does the whole shaft assembly etc need to be broken down?
    Last edited by wjstewart; 08-13-2008 at 12:40 PM.

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by wjstewart View Post
    ...Carbs etc. are very clean...

    ...Put ten hours or so on ski the first weekend I bought it. Top speed that weekend seemed to be around 50 mph, full of fuel and I weigh about 170 lbs. this speed was figured by comparing with my brother in law's old boat I was riding beside..Not sure how accurate that is.

    Plugs/wires and air filter appear to be brand new. No problems so far and trying to keep it that way with preventive maintenance.

    Can you tell me about the sealed drive shaft coupler. I've been told to use a needle type injector to lube the coupler through the thick rubber o-ring on the rear side (side closest to rear of ski), can this be done, or does the whole shaft assembly etc need to be broken down?
    Have you downloaded the 1992-1998 Polaris Service Manual?

    Only accurate way to measure speed is to strap a hand held GPS to the machine, and go for a ride on smooth water. The SLT780 has a fair amount of power, not sure what the GPS speed should be - something in the mid-50s...?

    There is no air filter. There is a flame arrestor, which will last the life of the machine. Occasional cleaning is all it needs - not much dust out on the water!

    The main concern with the carbs is the internal accumulation of sludge and gum over time, which clogs the tiny fuel passages inside.

    These 2-stroke engines will produce great power, even if they are running lean in one cylinder, with too little fuel flow. A piston can literally burn a hole through the top from lean operation, and the rider can be unaware of any problem until the piston is destroyed.

    That is why there is a consistent emphasis on here to ensure the carbs and fuel system are 100% good.

    You can ensure that the carbs are clean by taking them apart, and cleaning them internally. Not that hard to do, be sure to use genuine Mikuni parts or rebuild kits. If you prefer, there are services that will do the whole job for you - cost about $50 per carb, plus parts and shipping.

  6. #6
    Obviuosly I am not familiar with all of the terminology yet. But thanks for all the great information and tips.

    Yes, I have downlaoded the manual from beerdart

  7. #7
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Quote Originally Posted by wjstewart View Post
    Now for two more questions! Can anyone tell me can the sealed drive shaft coupler be lubricated without tearing ski apart?..I have been told that a needle nozzle on a gease gun can be pushed in the rubber o-ring to lubricate this.
    There is a plug in the side of it if it's the solid steel couple,you can replace it with a regular zerk fitting, They do make a cone shape adapter for grease withthe one in there now.

  8. #8
    96 slt 780...there is no hole plug or otherwise that I can see..I have spun it around..It is sealed with a large rubber o-ring on the back that seals around the shaft..no place for anyhting but a grease needle to poke through the rubber o-ring that I can see..Again excuse the ignorance!

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by wjstewart View Post
    96 slt 780...there is no hole plug or otherwise that I can see..I have spun it around..
    It is sealed with a large rubber o-ring on the back that seals around the shaft..no place for anything but a grease needle to poke through the rubber o-ring that I can see..Again excuse the ignorance!
    If the coupler is about 3 inches in diameter, then it is the bonded rubber type, which has no grease fitting.

    The only ways to grease it are to pull the drive shaft out (which means pulling the jet pump off), or using a needle shaped tip to squirt grease in beside the splines.

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