hangs at 5000 rpm

[old guy with kids boat]

Hey guys, I'm kind of stumped. 787 rev right up to 5000 hangs there for maybe 45 secs then slowly planes out. After another 5 or 10 secs it jumps to 6500 -7000 rpm have to hold it at about 3/4 throttle to get it to do this. Acts like Rave valves sticking but they are new this year and cleaned them anyway. Rave bellows replaced last year. water Rave rebuilt last year. If I pull choke it bogs the engine. Also it will repeat this over say 20 mins on water never jumping to 6500 rpm always have to feather it up. Then after the 20 min or so period it will just hang at 4800 rpm and can never get back up to 6500 again until later in day. throttle cable adjusted, low speed jets 1 turn out high speed jets at 0 acceleration pump adjusted to spec. oil pump adjusted to spec. Carbs rebuilt last spring and only have about 5 hrs on them. idles fine at 1500 rpm.

 

[racerxxx]

Are you running the slotted raves?

Like this one

 

[old guy with kids boat]

Yes they are slotted. new this year. when I pulled them they were kind of gummed up. I cleaned them and saw no change in performance.

 

[philipl]

I have the same trouble... i working on since a couple of month...

 

[old guy with kids boat]

sorted it out myself

 

[racerxxx]

Well?????????? What was it? Please post to help others in the future.

 

[old guy with kids boat]

Any number of things may have fixed it. rebuilt carbs, again. found one of the rave valve housing bolt was bottoming out before compressing the gasket so I had oil seeping out that side of housing, ground bolt down. However I suspect it was foolishly having inserted the rave valves upside down in the slides. No "top" markings on them so until I watched a video on grinding rave valves I suddenly realized they were rotated 180 deg. stupid mistake. Now I just have to sort out it stalling upon slow throttle up from idle. It starts and idles fine (a little high at 2000) and rips from 3500 - 7000 I suspect when I get idle down and accelerator pump readjusted as well as oil pump that problem will dissipate. It's a hunt and peck game for me, cause I get little input from others.

 

[racerxxx]

Your out of water idle should be 3k, that will put you at roughly 1500 in water. Do the carbs spray when you hit the accel pump? You carb test the accel pump diaphragm just hold your finger over nipple after activating it. The arm should stay, if not the diagram might be shot.

 

[racerxxx]

I know it can be rough getting answers immediately, but please remember we all have boats and skis and like to get out on them too.

 

[old guy with kids boat]

ordered a new diaphragm from OSD with carb kit when I rebuilt carbs this time.

 

[racerxxx]

Do you still have the original tubing going to the little injectors on the carbs? There is a little "restrictor" in there make sure that's clear

 

[racerxxx]

It goes one way, I believe it's a tapered hole, so pay attention

 

[old guy with kids boat]

Ok I'll check when I go to camp this weekend. Thanks

 

[Teebsa]

I'm having the same issue. I have the standard rave valves, not the slotted ones. They were cleaned out and seem to functioning as they should. The slots were just to help keep them from gumming up correct?