What now

[lmntguy]

97 challenger 787 10 hrs on rebuild OEM carb rebuild new rave and water valve bellows last year. Everything is adjusted to service manual specs. WOT 6500 rpm used to be 7200 have to yo-yo the throttle to get it to jump after planing out around 5000 rpm. Plugs are a light chocolate brown rave valves move freely and are turned all the way in water valve out to factory spec 3 1/2 turns out I believe. Idles and starts fine, 1500 rpm in water Engine dies if you pull choke out underway so it's not too lean. Seems like rave valves sticking but they are slotted and all free. Ideas?

 

[etemplet]

I had the exact same problem but at a lower RPM. It's like it can't get over the hump. What's your Pop-Off Pressure ?? Did you replace the needle and seat and/or spring. My issues got better as I increased the pop off pressure. When I purchased Genuine Mikuni Needles and Seat and went with the Mikuni "black" spring my pop off pressure went to 38psi and the ski performed much better. After I slotted the rave valves it made a huge difference. Make sure those three little holes in the carb barrel are flowing very well.

 

[lmntguy]

Carbs were just rebuilt and set up by an authorized SeaDoo repair facility and it it has slotted valves already. I going to replace the o rings on rave valves because all I can figure is they are hanging up at times. hoping it's that or the seat is worn because I notice a little oil seeping out the PTO rave valve.

 

[etemplet]

When my ski did that it was the carbs and that would be the first thing I'd check.

Unless the raves are really dirty I can't see them being the issue but it is a good idea to check and eliminate them. I'm not that adept at which bellows is good or bad besides OEM being the one you want but some are definitely thicker and may be preventing the valve from functioning properly. That O-ring isn't going to make the raves hang up that will let hot gas into the bellows area and melt stuff. On the oil seepage that is not uncommon.

A leaking water control valve can definitely account for the drop in RPM up high.

Question is... why did the engine go to the shop in the first place? Was it running fine and then "not" when you got it back?

 

[lmntguy]

The engine went back because it ate a ring in the PTO cylinder it is the 3 rd rebuild 1st 2 my fault I believe. Water valve is not leaking except maybe a little and I mean very little seepage around threads, water valve bellows replaced. My son took it out tubing this weekend and said it ran pretty good in the morning even seemed to hit 7000 RPM for a while. Then in the afternoon he said it would be ripping along and then suddenly cut back to 4 or 5000 rpm for a bit then he could take it back up. Didn't seem to be overheating plugs looked fine. I'm just snakebit with this boat, I've had it 4 years and have yet to get a full season out of it...

 

[etemplet]

Yep... strange. I can see why you suspect the rave valves. These engines are "sneaky" and difficult to diagnose. Check your spark plug wires. Maybe snip that lil 1/4" off and replace with a ty-wrap. I'm chasing my 787 once again. LOL Rave valve issues.. Good Luck Sir !! Post up on your progress.