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  1. #1
    CoastalGSD's Avatar
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    Red face Suggestions needed--starting a SL 780 that has been sitting for several years

    Greeting from a newbie!! Hoping to learn a bunch from this group of very savy folks!! I have been reading threads for the past few days, and have learned some very interesting things, so I am hoping for some suggestions for my ski.

    It is a '96 SL780 that I have owned since '97. It was fun for several years, and then life happened, and it has been sitting for a long time. It probably has less than 100 hours on it. It has not been in the water for about 10 years. I think I started it for a few minutes about 3-4 years ago. It sat in inside storage for several years, but has been outside in my yard for the past 2 years. I read some of the "stickies" about replacing fuel lines and re-building carbs due to age, and am all for that. My question is would it be safe to try and start it to see if it even turns over??? Can engines "lock up" from just sitting?

    I plan on siphoning out any gas that may still be sitting in tank (haven't looked yet), and putting fresh plugs in.

    A few other details:

    The MFD appears to be non-functional...no signs of life last time I put battery in ski.

    Ski has always been used in salt water. I was pretty OCD about washing/flushing entire ski and spraying everything with silicon and/or WD40. Engine "looks" clean and no rust or pitting.

    Ski has not had any major repairs or replacement parts put on....I think it went in once for a carb adjustment, but that was at least 15 yrs ago.

    Are there any physical things to check for before attempting to see if motor turns over??


    Any and all suggestions appreciated!! I would really like to get the ski going again and get to enjoy the water again!! Thanks in advance!!


  2. #2
    MFD problem may be caused by blown 1/4A fuse located in electrical box.

    I would put some oil down spark plug holes before tryng to start. Also premix oil in gas in case injection system isn't working right.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    The main concern is rust inside the engine. The cylinder walls are iron and the bearings in the crankcase are steel. You can either dribble some oil in it and 'hope for the best' or you can directly inspect. Inspection would involve removing the cylinder heads and the intake manifold so you can peek into the crankcase and see the cylinder walls.

    Even if you get it to start, that does not tell you much about the condition of the bearings, etc. Even a small amount of rust in the bearings can grenade within minutes when the engine is running at 6000+ RPM wide open on the water. If the bearings do fail the risk is that it further damages the engine, making engine rebuild even more expensive.

    Different guys have different approaches to resurrecting an engine that has been sitting for a long time. One method is to dribble some 2-stroke oil into each cylinder, let it soak for a while, bump the starter occasionally. Lay rags over the spark plug holes, then crank it for a bit to ensure excess oil is not present. Also dribble some oil into the crankcase or spray fogging oil in while cranking. Avoid excessive amounts as you do not want to draw liquid oil into the combustion chamber.

    Prime the engine with a teaspoon of gasoline down each carb throat or a few drops into each spark plug hole, then install spark plugs and fire it up.

    Check cylinder compression after verifying it will crank properly. Running on land can happen even if some cylinders are down on power. Compression check provides a baseline check. All spark plugs out, throttle held wide open, strong battery. Check each cylinder at least twice to confirm consistency. Write down the numbers.

    Oh yes, have a look at my signature links. Lots of useful info in there.

  4. #4
    CoastalGSD's Avatar
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    Thank you both for the suggestions! I will pick up a fuse to check the MFD, and hopefully it will come back to life. I will have to wait until this weekend to start opening up the cylinder heads to see what the inside looks like. Hoping for the best. I glanced at it tonight before it got dark, and I can see that several hoses have evidence of dry rot/cracking, so I have a felling there will be a lot of stuff to replace and check. Hoping this will be a fun project with a positive outcome. Time to start a parts list!! Time to start reading more threads...I really want to learn how this stuff works....wish I had taken the initiative years ago. Never too late to learn though!

  5. #5
    I went thru my '95 & everything I opened up was deteriorated & ready to fail. Spend the time to go thru all systems now & avoid frustration out on the water.

  6. #6
    CoastalGSD's Avatar
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    Well, I did not want to wait until this weekend, and still had a little bit of daylight after I got home, so decided to take a stab at it and removed the cylinder head covers....to my inexperienced eye, the cylinder walls do not look too bad. Front and center look smooth, and the rear has a slight bit of rust starting...

    The little oval gaskets on the intake manifold seem very brittle...no surprise. There is a bunch of corrosion on the gasket that is perpendicular to the cylinder housing by the front cylinder.

    I'm guessing that if I keep going down further into the motor to do visual inspection that I will have to get a bunch of gaskets....I am wondering if they are all dry rotted/brittle to the point of having a failure if I try to start it...again, I will defer to the experience of all you experts... I agree with your thinking...better to check first and do repairs on failing/tired parts than to risk a catastrophic failure by trying to cut corners...


    I will get a new battery this weekend, and a fuse to see if the MFD comes back to life.

    Please let me know what you think of the condition of the cylinders, and how I should proceed! Thank you again!!

    Sorry for the strange looking lighting...I was using a flashlight as it was getting a bit dark out....the second pic is showing the rust on the rear cylinder

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  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    What is that stuff that looks like crude or erosion on top of this piston?
    In particular just behind the fuzzy stud in the foreground.


  8. #8
    CoastalGSD's Avatar
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    All of the pistons have some dark black residue on the top....I have no idea what it is. It is dry and does not rub off (at least not by just scraping with my finger). So, does that mean the pistons are toast?? Should I try to hit it with a rag and carb cleaner just to see if it comes off?? (Bad analogy, but it almost looks like the residue you get when you are trying to burn off the rack on a gas grill). I did not have time to investigate as it was getting dark....just wanted to get the tops off to look, and then put them back on. Also, is there supposed to be a gasket or sealant between the cylinder housing and cap?? I apologize in advance for my lack of knowledge pertaining to the workings of the PWC....it is fascinating and I do want to learn . I am also very good at following directions and taking instructions from those who have experience!!

    I will try to get some pics on friday afternoon with the normal sunlight...I think the reflection of the flash from camera is making it look funky too. There is definately some "crud" there, just don't know what it is...

  9. #9
    BlueFishCrisis's Avatar
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    Those look pretty normal to me, especially when you look at the pic of the three together. It just looks like an overly rich MAG (Front), and somewhat lean CEN (center) and PTO (rear) settings. The black is carbon deposits from the combustion process. The "clean" areas are where fuel did not completely burn off and "washed" the piston clean. Therefore, the MAG piston is very rich which means it has been getting much more fuel than required for normal operation. There may have even been water intrusion, due to a leaky head gasket.

    Terminology for your info: Cylinders are what the pistons sit in. Heads cap off the cylinder and hold the spark plugs. The water rail is what was bolted to the top of the three heads, and carries cooling water away from the motor. Head gaskets are installed between the cylinder and heads.

    With that said, I assume the "brittle" oval gaskets you are talking about are the ones between the water rail and the heads....

    The cylinders do currently have head gaskets installed. You can see a small "fin" and some small brass rivets attached. These are steel and will likely need replaced. Some of the gaskets can be reconditioned with copper gaskets spray and reinstalled, but this does not always work.

  10. #10
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Looks good up top.

    But you still need to know if the crank is good or not.

    Quickest way might be to disconnect the exhaust header from the rear cylinder and pop the rear cylinder off. I did this on one of my skis and it was simple enough to hack a replacement header gasket to put it back together with.

    Assuming it was stored nose up the rear of the crank will be where the water was/is...and it is the easiest cylinder to remove/replace.

    Course if you're gonna do the carbs and fuel lines and all then you may just want to pop the intake manifold off when the carb rail is out and take a peek in that way.

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