Rotax 215 surge

[martinryk]

soo, I’ve got a mini jet boat with a Rotax 215 in it either 04-06 not too sure, anyways… I have this weird surge at 6500 RPM always happens at that RPM, I can power through it and it’ll be fine in higher RPM’s but right at that 6500 mark it always does it, wondering if anyone else has experienced this or might have any idea on what to look for, I did the quick finger check on the super charger and it was fine, will check it properly later this week, but I will post a video clip of it surging. I do have the candoo diagnostic tool, no active codes, in the last month or 2 it’s gotten a new impeller 13/18, already had a stainless wear ring in it and I’ve also put on a new pump seal when I did the impeller.

Thanks

 

[MacSeaDoo]

My thoughts:

1.. How old are the plugs? I replace the plugs each season...period. They are cheap and these machines are high strung with high piston pressures.
2.. Did you pressure test the Intercooler? I had surging and it was a leak in the IC. I am in brackish water so could actually see evidence on the plugs. I replaced the IC, surging went away.
3.. I also had a stumble at specific RPM. It was a bad coil. Coils are expensive, so I bought 1 and rotated it through the 3 and found the culprit.

Lastly, check the MAP sensor as well to make sure it is clean.

 

[martinryk]

Plugs were done in June, purchased from dealership, I did pressure test the intercooler the day after I made this post, I had an external leak, where the hoses go onto it, was kinda thinking of that may be an issue? While I wait for one to come in it did just JB weld the top and then took it for a test, still doing same thing, but doesn’t seem to be leaking anymore, coils are next my list of things to buy. I will have to check the map sensor when I get home .

 

[mkov608]

Check for an exhaust leak; the easiest way to do that is to get a can of Sea-Foam spray, follow the instructions on the can. When you run the engine after treatment, it will smoke like crazy; if you have an exhaust leak, you'll find it.

One of my '02s was surging like yours and it was a bad j-pipe. Exhaust gas was filling the bilge and getting sucked into the engine intake.