Cleaned Rave valves now stuck below 4,000 RPM

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Hello experts! First time post and you all have given me a lot of useful info so far and hope you can help me again.

I have a 1996 Challenger with the single 787 engine. I cleaned the rave valves yesterday and took it out on the water today for a test run.

It appeared that the valves have not been out since the boat was new. Initially, the boat accelerated much better than before, and was getting much faster than before. After bringing the throttle back to idle, I tried to accelerate again, and it will only get to 4,000RPM and about 10 mph.

I pulled the boat out of the water and tested it on the trailer where it got up to a quick max RPM. I put her back in the water and the same thing. Idle out, accelerate very well, idle, and stuck below 4k.

Possible cause, but not sure. My rebuild kits are a few days out, so I just cleaned and put everything back together.



BTW, I used the search function and was unable to find this issue. This is my first PWC so highly possible ignorance on my side.

Back story on the boat. I just got it from a relative where is sat for 2 years. First run basically stuck at idle. After replacing all the fuel lines, cleaning all the fuel filters and carbs, draining and replacing gas, replacing plugs, and running sea foam it ran well. Would only top out about 28mph, but started, idled, and ran well.

Thanks for any ideas, and again, thanks for all then info I have used on this forum to get the boat back on the water.

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It's pretty easy to get a gasket rub on the rave valve. That will stop them from moving freely, not opening fully or not closing. Also it is not uncommon for an engine that hasn't been run in a while to develop issues after the first couple of hours of operation. Usually the carbs. All the funk in the lines gets loose and plugs things up.
 
You really need to go through and rebuild those carbs. Rebuild the raves when the parts come in and see what it does, but I think you’re going to have to dig further into the carbs to get it running right... Use only genuine Mikuni carb kits and follow the carb rebuild sticky to the letter...
 
Just found my issue. When I put the rave valves back together, I didn't seat the bellows in the assembly. Just took the boat out for an hour and ran great.

Glad it was an easy and free fix.

It could still use a carb rebuild, but for now, all is great.
 
Well I’m going to put this out there. If you “think” you still need a carb rebuild, you do. That’s the number one cause for fried pistons in these things. People know there is a carb issue and ride it anyway right until the motor seizes...
 
Well I’m going to put this out there. If you “think” you still need a carb rebuild, you do. That’s the number one cause for fried pistons in these things. People know there is a carb issue and ride it anyway right until the motor seizes...


I guess I would be in the “ride it till it dies” group with out this chat. It idles great, and top end is running smooth, just a little choppy in the midrange.

Thanks for the heads up.
 
I guess I would be in the “ride it till it dies” group with out this chat. It idles great, and top end is running smooth, just a little choppy in the midrange.

Thanks for the heads up.
To each, his own...but I echo what JeremyD615 has suggested.....get into those carbs as soon as possible, follow the sticky post....the boat will reward you with even better performance (in all likelihood :thumbs-up::innocent:)
 
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Well, I rebuilt the carbs with genuine mikuni kits, and not the boat runs fine on the trailer, but under load in the water it can't pass 2,000 rpm without bogging down and dying.

I was able to nurse it up to 5,500 once.

Spent a couple hours trying to adjust the low speed valves, but no luck.

Any ideas?

I followed the guide on this forum, kept the original springs.
 
All the cables are hooked up and adjusted correctly? What was your pop-off setting?
You may need to make an auxiliary fuel bottle (feed) and run the boat disconnected from the fuel system.

I check my fuel systems by pressurizing from the carb to the fuel tank. I test both sides of the fuel valve and it's function. If I have a leak I break out the soap solution and look for bubbles. This still did not reveal a problem at had at the fuel baffle connection. I had a bad clamp that tightened up the hose but locked up and made me think it was "home." I'll find out about this next time I run the ski. LOL

Sounds to me like you have a carb issue. Did you replace your rectifier? What's your battery voltage while running?
 
All the cables are hooked up and adjusted correctly? What was your pop-off setting?
You may need to make an auxiliary fuel bottle (feed) and run the boat disconnected from the fuel system.

I check my fuel systems by pressurizing from the carb to the fuel tank. I test both sides of the fuel valve and it's function. If I have a leak I break out the soap solution and look for bubbles. This still did not reveal a problem at had at the fuel baffle connection. I had a bad clamp that tightened up the hose but locked up and made me think it was "home." I'll find out about this next time I run the ski. LOL

Sounds to me like you have a carb issue. Did you replace your rectifier? What's your battery voltage while running?


I agree that it's likely a carb issue. I haven't checked or replaced the rectifier.

I'm gonna tear it down and check the pop off after I do a cylinder pressure test.

I haven't searched for a fuel leak yet, but not a bad idea since I've replaced all the hoses and clamps.

With these boats, do the fuel lines pressurize as soon as power is applied or do I need to start the engine?

Also, anyone have a way to clean the fuel tank out? After replacing everything and cleaning all the lines, I still had a good amount of gunk in all the filters.

Thanks as always. I appreciate the help these forums provide.
 
Just got my equipment in to test pressure. Cylinders are both just under 110 so from the looks of it, a rebuild is in my near future.

Pop off was about 23 and 30 on the other so a little low on one. Adjusted and will see if I can get it going.
 
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