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  1. #1

    1998 Pro 785 Problems starting in the water

    I recently purchased a 1998 Pro 785 with 6 hours, it literally looks like it came right off the showroom floor. The ski was being sold by a local jet ski store on consignment, prior to my purchasing they did a full tune up and test of all systems and gave the ski an A+ bill of health. Fast forward two weeks, I prepare to take it out to the lake, the ski starts out of the water no problem... I take the ski to the lake for the first time and it fails to start in the water after several attempts. I take the ski home, charge the battery, check the voltage and everything checks out. After starting it several times out of the water, I decide to take it out to the lake for a second attempt. Sure enough, once again it WON'T start in the water?!

    I'm a rookie to watercraft ownership, but have ridden and been around boats and PWCs my whole life and am baffled by why this is happening. Any guidance or insight would be much appreciated!

    -Robbie


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    If the shop did not water test the machine after their tuneup, then it is possible there is a problem they did not notice.

    The first thing I would suspect is the battery. Is the battery new?

    Use a decent quality multi-meter to measure the battery voltage while cranking the engine, with the lanyard out. The engine will not start, so you can watch the battery voltage for a few seconds while it cranks (maybe 10 seconds cranking time).

    A strong battery will be able to hold the voltage well above 10.6 volts while the engine is cranking. If the voltage sags to near or below 10.6 volts then the battery is weak. Even a fully charged battery can be internally weak.

    Set the MFD display to show RPM. Crank the engine and see what RPM it shows while cranking.

  3. #3
    Hi K447-

    Thanks for the welcome and prompt reply!

    The battery is brand new and fully charged, I will run the multi-meter test this week and report back. I need to clarify with the shop whether they water tested or not.

    I appreciate the response and will report back soon!

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    Does it even fire on the water? Does it sputter a few times and die? Will it start and run if you hold the throttle in at all?

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    they can be a pain in the ass to fire in the water sometimes try choking it for a few seconds and if it doesn't fire take the choke off and hold the throttle wideopen and crank the hell out of it also do a compression check too

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    Yeah... I know on a Weber (MSX 150)... low compression will make it very hard to start in the water. But it'll fire right up on the trailer. If you tip the ski up on it's side to get the exhaust out of the water and to unload the jet pump a little... that'll usually do the trick (if your issue is caused by low compression).

    So, yeah... check compression on it too.

    Cheers!

  7. #7
    It won't fire at all on the water, it cranks and wants to fire but never turns over.

    I've tested compression, all three cylinders read 130. So I don't think it's a matter of compression.

    I've thought about firing it on the trailer prior to launching, but am nervous that it won't refire after I shut it off in the water.

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    Even if you give it throttle? Give it some throttle and get it to fire.

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by rbod01 View Post
    It won't fire at all on the water, it cranks and wants to fire but never turns over.

    I've tested compression, all three cylinders read 130. So I don't think it's a matter of compression.

    I've thought about firing it on the trailer prior to launching, but am nervous that it won't refire after I shut it off in the water.
    Until you are confident that it will start on demand while floating, keep it strapped to the trailer..

    You can back it down the launch ramp while still strapped down, front and rear, to the trailer. Back it in until the jet pump intake is fully submerged. Now you can test as needed, and if it starts you can run the engine as long as necessary since it will have full normal water cooling.

    What is the idle RPM with the engine out of the water? It should be something over 2000 RPM when running out of the water.

  10. #10
    Thanks for all of the advice, I'm planning to take the ski out to the lake this weekend to "trailer test" it. I will report back.

    By the way, battery test was all good.

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