Cavitation issue

[BigT51]

Had an issue for the first time this past weekend when pulling my son on his wakeboard. When getting him up (he's only about 130 lbs), one of the impellers would cavitate as I accelerated to planing speed - it didn't happen immediately but after I was accelerating for a couple seconds. This hasn't happened before but we also haven't tried wakeboarding with 9 people onboard - 8 in the boat including two small children plus 3/4 tank of gas. I'm assuming the additional weight is what was creating the issue but I didn't experience the cavitation at any other time and it seems to be only on one impeller, I believe the port one. No changes to top speed or any other performance issues. Anyone have any ideas? I need to check the intake thoroughly for missing silicone - couldn't see any missing but I didn't get under the boat and look hard at it. Just thought I'd put this out there and see if anyone has seen this before.

 

[Scottintexas]

I wouldn't be to concerned about it yet, you had a boat full of people and you were still able to wakeboard,

it could have been trash in the pump and next time out it won't happen,
or it could be a impeller ding or silicone issue, either way continue to enjoy the boat until it causes a performance issue,

when i had my missing sealant issue I was able to "nurse" it through a rpm zone and then it would go away until I was able to fix it correctly,

pull the impellers and it will be very easy to see everything,

 

[Chewiem16]

I just started having a similar issue on my SX240. Starboard side hits 6200, and then bounces back and forth to 6500. as the port side climbs to 7100 (max rpm, I have solas impellers). If just started happening out of nowhere and the are clear.

Is this what's happening to yours too?

checkout the video:
SX240 Engine Surge

 

[BigT51]

I just started having a similar issue on my SX240. Starboard side hits 6200, and then bounces back and forth to 6500. as the port side climbs to 7100 (max rpm, I have solas impellers). If just started happening out of nowhere and the are clear.

Is this what's happening to yours too?

checkout the video:
SX240 Engine Surge

Mine doesn't pulsate, I've not seen that type of behavior before. It reminds me of running in waves and the rpms jump when the impeller comes out of the water then drops back in. My boat was accelerating to planing speed while pulling my son out of the water on his wakeboard and as he got about half way up, the port engine rpms would jump up briefly until the boat was on plane. You could hear and feel the impeller cavitating, there wasn't any pulsating. It didn't cavitate any other time, not even pulling a tube with three people on it. It has to be something with the flow of water to the impeller under the heavily loaded situation - the wakeboard provides a lot of resistance until it gets on top of the water, plus there were 8 people onboard and the gas tank was past 3/4 full. Your situation is different, and I've not seen it before. I'll be anxious to hear what others think it might be. The fact that they're solas is interesting, were the pitches different - were they marked port and starboard when you installed them? My understanding is the Yamaha impellers have different pitches.

 

[Chewiem16]

Yes they are 2 different pitches. I’ve had them on for 2 seasons now without any issues. This is the first time this started happening. Im leaning towards something electronic

 

[Murf'n'surf]

Try to replicate the cavitation on a less loaded boat and see what happens. Probably a weight/weight distribution issue. Have you looked at the impeller to pump housing tolerance? Should be a slight gap and no large chunks taken off of the impeller leading edges.