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  1. #1

    Join Date
    May 2009
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    San Bernard River, Texas
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    Ouch... Melted Intake Manifold - 2005 RXT

    I recently bought this 20 hour 05 RXT (kind of a fishy deal, but a deal nonetheless) and took it out this weekend to do an oil change and change the spark plugs.

    Background on the ski: It was a never titled demo that sat outside for 3 years without maintenance (supposedly). Seat is messed up and the gelcoat was dull... but I am replacing the seat with a RIVA cover and I've polished the hull back to a shine.

    It didn't run very good when I first took it for a ride after I bought it, but after running some fresh gas through it... and I had it up to about 68MPH. The following weekend I took it out and I was starting to lose RPMs and it was idling at about 3600 RPMs. I was hoping some regular maintenance would solve these issues.

    This past weekend, I took it out of the water (I store it on a lift on a river) to change the oil. I hooked it up to the water hose and it started idling at about 6000 RPMs. No bueno.

    Start pulling stuff off to look down into the engine bay and notice the intake manifold is melted. Pictures attached... ouch!

    I take the plugs out and notice one plug looks like it has been crushed/melted. The side electrode is touching the center electrode. I start thinking the worse and expect to see a ding on the piston.

    I ended up pulling the intake off and eventually got the head off. One of the intake valves on the cylinder that melted was discolored and wasn't seating right. Put a flashlight behind it and you can tell the valve itself (not the stem) is warped and not sealing. The rest of the head looks fine... not warped and the valve walls look just fine.

    I looked at the pistons and they do not look like they touched anything and the cylinder walls look fine. I was pleasantly surprised. I think the bottom end made it through without harm.

    I dropped the head off with the local SeaDoo dealer and he is going to replace the valve that is obviously warped and look at the rest of the valves in that cylinder to see if they need to be replaced to. Since the ski has such low hours... the tech and I agreed replacing all the head components while we have it off is a bit overkill.

    His theory on what happened was air got into the intake manifold via a crack or bad gasket on the fuel injector, leaned the motor out and heated up that cylinder and when that valve cooled... it warped.

    Anyone ever seen anything like this on a 4tec? Thoughts? Opinions? Things I should check while I have the motor this far apart?


    Sorry to ramble on my first post. I've been reading this site for a while and it has been very helpful thus far.
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  2. #2
    Vern's Avatar
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    May 2005
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    Well BRP upgraded the valves in '06-up skis and the 04-05 valves occasionally fail. Pulling the head off is a bit of work so my two cents is that NOW is the time to consider what mods you may want to do in the future. If you ever want to go with a higher rev limit aftermarket ECU now would be the time to do the Riva valvespring upgrade. At the very least I would strongly consider putting in all new upgraded Sea-Doo valves or Ferrea valves. If you are 100% sure you will never mod the engine much, I still would think about replacing all the valves ... one less thing to fail on your ski. Another item to consider for reliability is replacing the flywheel bolts too (in the PTO cover) ... they were also upgraded and the newer ones are stronger. I would carefully check the head to make sure it is 100% flat, and consider decking it ... especially since one cylinder got hot, there is a chance your head is slightly warped.

    I am assuming you already replaced the ceramic washers in the SC with Riva metal washers too? That is the number one thing to do to prevent expensive future problems ...

  3. #3
    HOSS's Avatar
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    Exhaust valve seat and burnt valve. Valve could even be bent.

  4. #4
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    May 2008
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    I took it seriously

    when I was told a proper winterize of a 4-tec required pulling the intake manifolds and fogging directly onto the valve stems. Leaky intake valve may have let hot exhaust gas melt the manifold. I'll certainly keep this in mind when I'm looking at similar "deals"

  5. #5

    Join Date
    May 2009
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    San Bernard River, Texas
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    Quote Originally Posted by Vern View Post
    Well BRP upgraded the valves in '06-up skis and the 04-05 valves occasionally fail. Pulling the head off is a bit of work so my two cents is that NOW is the time to consider what mods you may want to do in the future. If you ever want to go with a higher rev limit aftermarket ECU now would be the time to do the Riva valvespring upgrade. At the very least I would strongly consider putting in all new upgraded Sea-Doo valves or Ferrea valves. If you are 100% sure you will never mod the engine much, I still would think about replacing all the valves ... one less thing to fail on your ski. Another item to consider for reliability is replacing the flywheel bolts too (in the PTO cover) ... they were also upgraded and the newer ones are stronger. I would carefully check the head to make sure it is 100% flat, and consider decking it ... especially since one cylinder got hot, there is a chance your head is slightly warped.

    I am assuming you already replaced the ceramic washers in the SC with Riva metal washers too? That is the number one thing to do to prevent expensive future problems ...
    Thanks for the reply. I don't plan on doing much work to these skis... otherwise I definitely would swap valvesprings etc.

    I worried about the head being warped as well. The head gasket looks good and I didn't see any blow-by. I've checked it with a straight edge briefly, but I am going to have the SeaDoo tech check it to specs. The head (besides the warped valve) looked good... but you're right, it's worth checking.

    I haven't changed the washers out, but I've read about the importance and probably need to do so soon... $220 is a lot for four metal washers though.

  6. #6
    Ride Hard! aha's Avatar
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    The washers are 100 bucks in Jerry's store.

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