Surging rpm’s after cavitation issue repaired by dealer 2015 AR190

[stevefarfar1]

Hi there. 2015 AR190. Had some corrosion issues on the jet pump, leading to major cavitation earlier this year. Dealer rebuilt a lot of the jet pump. About 5 weeks and $2k later, put the boat back in the water. Works pretty well overall, but now I’m seeing rpm oscillation (feels like surging) at constant throttle.

Oil and spark plugs are new 6 weeks ago. Fuel is treated at every fill up. I pulled the plug and couldn’t feel anything in the intake or impeller.

Seems like maybe it’s still a cavitation issue and the dealer missed something? Would love any ideas to check or if anyone has had a similar issue or there are other things to consider! Thanks

Link to video you can see rpm’s moving and hear the engine surging…

 

[sunbyrned]

Have you tried it on the trailer? I don’t know if you can idle wide open like that on the trailer for any good period of time. Just curious though if it’s caused by water resistance from going over waves rather than fuel supply. Just a thought.

 

[JBehrens]

I had the same issue on my boat and it turned out to be the ignition coil on the #4 cylinder that was bad, this was figured out by a noticeable difference in the #4 spark plug, the #4 was not firing. If you can check the coils/plugs and see if anything looks off. Wrong spark plugs? / Spark plugs burned