New 787 RFI rebuild Running Issue

[elnook909]

For the folks who are knowledgable about these 787 RFI's, I have the 2002 model, would you be able to give me advice on troubleshooting steps?
My RFI has a rebuilt engine from reputable shop with fully rebuilt top and bottom end motor
Immediate startup out of water running on hose and in water too
new spark plugs
New Bosch OEM fuel pump and all filters inside fuel pump
cleaned tank added fresh non ethanol gas
New oil lines, filter and oil tank all replaced
Using seadoo BRP synthetic oil, set oil pump advanced for break in

What its doing

While in wake zone for 10 minutes to get to lake no issues running was able to throttle up a little with no issues
Once I gave it throttle to go fast out of wake zone it bogged down then started behaving
like it was running on one cylinder very slow and sputtering barely made it back
to the dock.
No maintenance light
Once I took it out of water I started it up with no issues
running fine again.
Any ideas where I can start troubleshooting with this? Any help would be appreciated.

 

[lavasioux]

Hmm...

I always like using a cheap spark plug tester to see if i have spark/ mpem is good.

Good luck!

 

[burtshaver2021]

I held off from replying here in hopes that someone more knowledgeable would answer but a couple of things maybe, do you know what your fuel pressure is? What it’s supposed to be? You will have to do some searching to see exactly how to do it, but might be a good idea to have a fuel pressure gauge that you can view while riding, temporarily anyways.

 

[elnook909]

Thanks thats a good idea I will find out how to check fuel pressure on the rfi

 

[tomanycars]

For the folks who are knowledgable about these 787 RFI's, I have the 2002 model, would you be able to give me advice on troubleshooting steps?
My RFI has a rebuilt engine from reputable shop with fully rebuilt top and bottom end motor
Immediate startup out of water running on hose and in water too
new spark plugs
New Bosch OEM fuel pump and all filters inside fuel pump
cleaned tank added fresh non ethanol gas
New oil lines, filter and oil tank all replaced
Using seadoo BRP synthetic oil, set oil pump advanced for break in

What its doing

While in wake zone for 10 minutes to get to lake no issues running was able to throttle up a little with no issues
Once I gave it throttle to go fast out of wake zone it bogged down then started behaving
like it was running on one cylinder very slow and sputtering barely made it back
to the dock.
No maintenance light
Once I took it out of water I started it up with no issues
running fine again.
Any ideas where I can start troubleshooting with this? Any help would be appreciated.

what kind of fuel pump did you use. You said you had the oil pump for more oil in break in,. how do the plugs look. are they real wet looking. I have the same the same skis . 2000 model rfi . rebuilt 787. I assume impeller is clear nothing got sucked up in there. battery is important they must be fully charged. throw a meter on make sure you are over 12 volts when running. 13 is good. I use the same oil and 91 octane, Have you had it out after the rebuild and it ran good or is this the first time.

 

[tomanycars]

For the folks who are knowledgable about these 787 RFI's, I have the 2002 model, would you be able to give me advice on troubleshooting steps?
My RFI has a rebuilt engine from reputable shop with fully rebuilt top and bottom end motor
Immediate startup out of water running on hose and in water too
new spark plugs
New Bosch OEM fuel pump and all filters inside fuel pump
cleaned tank added fresh non ethanol gas
New oil lines, filter and oil tank all replaced
Using seadoo BRP synthetic oil, set oil pump advanced for break in

What its doing

While in wake zone for 10 minutes to get to lake no issues running was able to throttle up a little with no issues
Once I gave it throttle to go fast out of wake zone it bogged down then started behaving
like it was running on one cylinder very slow and sputtering barely made it back
to the dock.
No maintenance light
Once I took it out of water I started it up with no issues
running fine again.
Any ideas where I can start troubleshooting with this? Any help would be appreciated.

Also you do know when running on hose to turn the hose off before turning off the engine.

 

[elnook909]

what kind of fuel pump did you use. You said you had the oil pump for more oil in break in,. how do the plugs look. are they real wet looking. I have the same the same skis . 2000 model rfi . rebuilt 787. I assume impeller is clear nothing got sucked up in there. battery is important they must be fully charged. throw a meter on make sure you are over 12 volts when running. 13 is good. I use the same oil and 91 octane, Have you had it out after the rebuild and it ran good or is this the first time.

 

[elnook909]

I purchased a new Bosch oem fuel pump. The oil pump is on the advanced notch .the impeller is clear and I am getting 13.87 v running at idle 1500 rpm the plugs are wet but light brown color. Thiis is the firstt time out after rebuild .

 

[tomanycars]

They may have those plugs for the fuel injection mixed up. the wires are color coded. what state are you in.

 

[elnook909]

They may have those plugs for the fuel injection mixed up. the wires are color coded. what state are you in.

Thanks I will double check that

 

[burtshaver2021]

Wouldn’t hurt to check the voltage regulator as well

 

[etemplet]

When I have weird problems with RFIs I throw in my spare MPEM... it has solved issues Twice.

 

[offgrididaho]

From the AI robot.

Based on your description, your 2002 Sea-Doo 787 RFI (Rotax Fuel Injection) is likely suffering from a high-speed fuel delivery issue or a RAVE valve malfunction. Since it idles fine but sputters under load, the engine is starving for fuel or air at higher RPMs.
Here is a checklist of what to check, ordered from most likely to least likely:

1. Fuel Delivery System (Most Likely)
The RFI system is very sensitive to fuel pressure. Low pressure at high RPM will cause a massive bog or sputter.

• Fuel Pump Pressure: This is the #1 cause for RFI bogging. Check that pressure is holding at 56-60 PSI (some 787 RFI models can be around 75-80, but it must be consistent and not drop when you throttle up).
• Internal Fuel Filters: Inside the fuel tank, the fuel pump assembly has two filters (a "pickup" filter and a finer filter inside the VST housing). They are likely clogged with debris or "brown sugar" buildup from old fuel.
• Fuel Injectors: The injectors may be clogged and unable to deliver enough fuel at high load.
• Grey Fuel Lines (Tempo Lines): If your Sea-Doo still has the original grey fuel lines, they decompose from the inside out and clog injectors and filters.
  YouTube +4

2. Electrical Issues

• Battery Condition: Even if it starts fine, a battery with low voltage or low "State of Health" (SOH) can make the ECU/fuel pump behave erratically at high RPM.
• Voltage Regulator/Rectifier: A failing rectifier can put out too much voltage (noise) and confuse the RFI computer (MPEM), leading to high-speed misfires.
• Spark Plugs: Check for fouled plugs. They might work at low speed but fail to fire under high cylinder pressure.

3. Engine Management & Performance

• RAVE Valves: Clean the RAVE valves. If they are stuck in the "down" position, the engine will run fine at low speed but won't be able to breathe (sputter) at high RPM.
• Throttle Position Sensor (TPS): The TPS might be faulty, dirty, or uncalibrated, telling the computer to give it less fuel than needed, causing a lean condition.
• Exhaust Water Regulator: A stuck regulator can let too much water into the exhaust at high speeds, killing power.

4. Other Potential Issues

• Intake Grate/Impeller: Check for debris in the intake grate (rope, seaweed). Sometimes it acts fine at low speed but cannot move water efficiently at high speeds.
• Compression: Ensure the engine still has healthy compression.

First Actions to Take:

1. Check fuel pressure.
2. Clean the RAVE valves.
3. Replace spark plugs and check for grey fuel lines.