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3 Posts
Discussion Starter · #1 · (Edited)
I have a Rotax 787 in a 96 SeaDoo. I have a very difficult issue and I'm trying everything. I can get the boat in water, take my time parking the car and such. Then with the boat sitting in water cold I can start it easily. No issue. I run the boat for any amount of time and it runs awesome. I'm getting 45MPH on choppy water and wind with a full tank of gas.

However, when I get to the dock and shut it off. I can turn it on within a few minutes no problem. But, if I wait too long it will not start under any condition no matter what I do. It is literally sitting there cooling off and it will never start. I inspect the plugs and they never get fouled no matter how long I try to start it. I have a few small bubbled in the return lines, with seemingly no entry points because the fuels system was pressure tested, and when I'm trying to start it those bubble barely move at all. Like fuel is not being pumped.

I've been over this so many times. Here's what I have done;
  • Replaced decrepit pulse hose with brand new reinforced fuel line hose
  • Carbs fully rebuilt with genuine Mikuni parts.
  • Pop off set to 35PSI in both MAG and PTO <- In Spec
  • High Jet to 0 and low jet to 1 full turn out
  • Idle set to 1500 RPM in water
  • Fuel lines all new, no green goop
  • Fuel filter brand new OEM
  • Fuel vent, selector and baffle inspected and perfectly clean
  • Fuel system pressure tested at 5 PSI for 15 minutes
  • Starter is good and using the 8 tooth gear (per seadoo) for more torque
  • Battery is brand new and fully charged with a smart charger. Grounding is also good
  • Compression at 140 PSI in both cylinders
  • Rotary Valve removed and inspected. Using solder method, per the book, I have clearance of .0125 when I measure the thickness of the solder <- In Spec. However there are lines in the valve, not deep but they are there. Nothing to catch my nail on. Does the valve look ok in the photos or is this blatantly bad even though the clearance is good?
  • I have spark on both plugs as tested with an inline spark tester
  • Spark plugs are a perfect brown so not fuel starved and not flooded
  • I've added a little fuel to the intake, as well as the cylinders themselves and it will not fire
I'll try anything else at this point. Take away is I have good spark, good carbs, seemingly a good rotary valve, good compression and a clean fuel system. I am totally at a loss as to why this is still happening.

Note: I don't know if this is normal, but I clearly hear a constant dribbling of water into the exhaust. It's as though it's coming in through the water valve or the exhaust box. But the exhaust pipe on the outside of the hull is angled upward so I think it would be tough for water to get in there. Regardless, I hear this constant dribbling like a faucet left on low and dribbling into a pan. Is this normal? Should water be dribbling into the exhaust when the boat sits in water? This seems off to me since it would be only a matter of time before the exhaust tank the tuned pipe connects to fills with enough water to bog out the exhaust.

Please help and thank you so much in advance!!

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3 Posts
Discussion Starter · #2 ·
Yesterday I got stuck at the dock due to a boat blocking me in. I had to shut it off and since I couldn't start it again I was stuck there waiting.

So I took the time to track down why I was hearing dribbling only after running. It seems that the water regulator valve is leaking water into the resonator after the boat has been running. Enough that I can hear it actively dribbling in there.

So, I was like screw it and I used my hose punchers to pinch off the hoses on the water regulator as well as the main water line from the pump to the engine. For the heck of it I tried to start it and IT FIRED UP!!!!

This tells me definitively that water is getting into the exhaust at a high amount while the boat sits in the water and I can see anything that would cause this. That is why it won't fire up and once I pinch those lines off, it starts perfect. I did it again this morning to test it out and it works every time.

So, now that I know why the boat won't start due to the water likely filling the exhaust, I need to figure out why this is happening.

As mentioned, water is actively dribbling into the lower canister of the exhaust that's connected to the tuned pipe. And unless I pinch that off, as well as the main water line form the pump, I have no way to start it. Once I pinch them off, it start perfectly every time. There is absolutely an issue with the water getting in.

Any advice on what to check would be great. And is water supposed to pour into the exhaust from the water regulator?

3 Posts
Discussion Starter · #3 ·
The starting issue is fixed!!!! All this time it was because the inlet hoses were not tied up in a high loop! I tested it out today and it starts on water when hot without issue now! I’m free to go anywhere on the lake and dock it. I’m so stoked you have no idea.
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