Need advice on engine loss of power

[Scubadave16]

Hello

I have a 1996 Sea Doo Challenger which was running fine until yesterday.

When I accellerate, I only get about 5500 Rpm out of the motor and it just bogs down. I had my buddy sit way in front and i managed to get it on plane and then the rpm went up to maybe 6300. Max speed about 30. last week it was much faster and ran about 6800 rpm.
I also notice a slightly different sound in the engine, maybe a bit more throaty and rumbly for lack of a better description.

so what changed? I filled up the gas tank. the gas came from the marina and I always fuel up there.

so what have I done?
I checked the plugs- OK, not fouled.
I checked the fuel filter- clean
a buddy suggested I check the RAI? valves on top of the cylinders. they move freely.
plug wires are connected and clean.
another buddy says I should change spark plugs, but i doubt that is the problem.

In addition, I notice that the gasket around my exhaust pipe through the hull is cut and water pours in when 2 big guys are leaning over the engine compartment. this seems unrelated, but thought I would mention it.

Another oddity, after testing it i heard a trickling sound coming from the muffler area. not sure what that was about. no water was leaking into the boat so it must be inside the muffler.

I am open to suggestions as to what might be going wrong and what I should try next.

Thanks a lot in advance for any help.

Dave

 

[Waterluvr]

The 787 needs a few things to be in good order to see WOT operation, Rave valve blades need to be clean and the bellows and o-rings doing their job so the exhaust ports are fully opening.

On the backside of that is another limiting factor that will restrict rpm's to the range you're experiencing, if you look on the resonator there's a water pressure regulator that's bellows operated if it continues to add water at WOT without closing the valve you won't see max rpm's there's a lower pinch clamp on the bellows that will put a small hole in it and cause the problem you're experiencing.

Fix the exhaust boot before the boat sinks! A roofing gasket can be substituted for the NLA one, while not exactly easy to work with one can be made to seal the leak. I might be able to find an original gasket seal part for you if you're ever in the neighborhood.

 

[2UCS]

Ido have 2 gasket's for the exhaust that i had on ebay if your interested. Its for 1996 Seadoo Challenger

 

[Scubadave16]

are they currently listed? I might be interested

 

[Scubadave16]

Thanks for the info.

I am kinda new to working on this boat. Is what you described above something a reasonably competent guy can do without special training/tools?
I would happily have a pro do it, but there is usually a 4-6 week backlog at this time of year and that pretty much uses up the rest of summer!

 

[Waterluvr]

Thanks for the info.

I am kinda new to working on this boat. Is what you described above something a reasonably competent guy can do without special training/tools?
I would happily have a pro do it, but there is usually a 4-6 week backlog at this time of year and that pretty much uses up the rest of summer!

It will take about an hour and a half including the learning curve for your first time to remove and clean the raves, replace the water valve bellows and head to the ramp for a water test I'm booked out until the end of summer but if you want to bring the boat by and turn your own wrench with some pointers and help your welcome to come by it's a piece of cake to do the work.

I have the OEM exhaust gaskets for your boat, that's a pain to change but if you want to spend a few more hours it's just a matter of needing an extra pair of hands at the right time as it goes faster with someone in the boat to get on the backside of the nuts and someone out to run them with a power tool so your not stuck in there forever.

My main shop is closed on Monday and I'm usually at my home shop that's "DIY" day and there's always a couple ski's and jet boats stopping by for pointers your welcome to join us launch ramp is less than five minutes away for a water test.

 

[Scubadave16]

Thanks a lot for the info! I am planning on getting into the repair this weekend I hope. Since I don't have the through hull exhaust gasket handy at the moment, is there any problem wiht just slathering on a lot of silicone caulk around the exhaust pipe bellows until I can get the real part later?
Also, I don't see any parts on the schematics for the "rear" RAVE valve, just the 2 front ones. Is the bellows the same on all 3? Do they recommend changing the bellows and o rings on a regular basis? My local shop didn't have any parts in stock and would only order them if paid for them in advance non refundable, non returnable.

 

[2UCS]

Thanks a lot for the info! I am planning on getting into the repair this weekend I hope. Since I don't have the through hull exhaust gasket handy at the moment, is there any problem wiht just slathering on a lot of silicone caulk around the exhaust pipe bellows until I can get the real part later?
Also, I don't see any parts on the schematics for the "rear" RAVE valve, just the 2 front ones. Is the bellows the same on all 3? Do they recommend changing the bellows and o rings on a regular basis? My local shop didn't have any parts in stock and would only order them if paid for them in advance non refundable, non returnable.

Are you interested in purchasing the Boot i have 2 but might only have 1 left by tonight.

 

[Scubadave16]

OK friends. I pulled the 2 engine rave valves and they were quite grungy, but no real problems with holes in boots or sticking or anything. I cleaned them up and reinstalled them. On advice of a buddy, I cranked them way down supposedly to get more low end torque while sacrificing top end speed.
I looked at the rave valve on the resonator and it seemed OK. no visible holes in the boot and it seemed to move freely.

when I put the boat back in the water it seemed to run OK, but still seems low on power.
When I give it full throttle, I get a MOMENTARY burst of maybe 7000 rpm for maybe 2 seconds, then it quickly drops down to the upper 5000s and then slowly as the boat gets on plane, it gets up to 6200 RPM. The GPS on my phone showed 34mph at full throttle. Maybe every 5th time I accelerate, I get a real bogging down and only get about 6000rpm at initial start up. it seems if i put in reverse and rev up the motor and THEN put it in forward and give it wide open throttle, it does better. BTW, there are no weeds or stuff where I am running the boat.

I don't have hard numbers but it seemed to be much faster earlier in the season.

so the question is what next?

I have ordered E3 spark plugs and I will change them out next weekend.
any other ideas?
Thanks again

 

[Dr Honda]

I wouldn't bother with any non-conventional spark plugs. 2-strokes eat plugs... so just use normal NGK's.

Anyway... start with the basics.

1) Compression. Check it. If it's low... you will be loosing power.

2) Rotary valve. If the clearance is high... you will loose power.

3) Flame arrestor. Clean it.

4) Carbs... clean them.

 

[Scubadave16]

Well, the plot thickens on my Challenger as of this weekend. I had pretty much decided to just run it as it is for the rest of the season since no one is really able to work on them this year (at least not around here). But today I nearly had to be towed in. I took the boat out. It accellerated somewhat choppily up to 6100 rpm. I was able to get it to 34mph. At each accelleration, however, it seemed to get slower and slower on the start. If I put it in reverse and got the rpm up to 7000 rpm then put it in forward, it ran better for one startup, but quickly bogged down. I still wasnt getting blinding speed, but was able to run the thing. Then when leaving the beach today, it just wouldnt start. I choked it, then put in full throttle and finally got it to fire up. But it hardly ran. It backfired, it stumbled, it made popping sounds. it seemed to run at idle OK except for the backfires and pops. But it wouldn't go over 3000 rpm and it sounded like hell. it had plenty of gas and oil. no odd smells or anything. just doesnt run worth a crap either in reverse, neutral, or forward. I barely made it into the harbor at just a few mph. back at the ranch I pulled the plugs, they look normal. I checked the plug wires and they were on solidly and not wet. in fact the engine compartment was pretty dry. the fuel filter was clear. the battery connections were solid. The only thing I didn't get into were the carbs cause I didn't have my allen tools. Now the boat is not useable. I am pretty disgusted. my buddy has the identical boat and I noticed earlier that his engine is about half as loud as mine at idle. not sure if it is an exhaust issue or something else or totally unrelated. If anyone knows how to fix this and is willing to work on it and is near me I will be willing to have a pro work on it.

 

[irishlad]

Has anyone tried threading the top part of the valve and securing it to the housing in the open position? Ive tossed this idea around since I keep melting away the caps even after I have replaced entire rave assembly to include valve and housing.

 

[Scubadave16]

Back to the saga of my Challenger. I looked at the carbs today. From what little I can see, they look clean. I shot gumout in both with no change. The engine starts right up, but misses and pops. Both plugs have an equal amount of trace carbon on them. If I give the engine gas, I get about 3400 RPM, but it sounds terrible and pops and backfires. I traced and jiggled the plug wires- nothing seems loose. There didn't seem to be anything else I can test. I DID notice the battery was a bit low, but I had been cranking it a lot and we had a TON of rain so maybe the pump was running. not sure if a related electrical problem.

The fuel is the same as in my other boat which runs fine. All purchased from the same pump at the marina.

I THINK I am looking at an ignition problem, but I really have no way to test this with only simple hand tools and a fluke meter.

I think I have 2 problems, though, I also had the loss of power/RPM issue which never was resolved. from what I have read on here it might be the water regulator in the resonator, but that valve looks fine. not sure how to test it and no real point when the engine won't run smoothly.

So this weekend, I am going to pull the boat out for the season since it is a big paperweight now. I will start calling around for repair shops that will take a look at it unless anyone has any great ideas.

Thanks
Dave

 

[Fat Tony]

Looking down the throat of the carb really does nothing as its the internal passages that get clogged up. You need to clean the internal jet passages to get all the crud out, just shooting a bit of gumout down the throat isnt going to cut it if the carbs are gummed up.... they have to come apart. But it could be one of several things. Dirty carbs, clogged fuel selector, wear on the rotary valve...

 

[Scubadave16]

Just to add info the compression on the cylinders is 147 and 152.