1998 Seadoo Challenger 1800 Won’t rev above 5k rpms

[CadeZ]

Hi guys. I’ve had several different threads dealing with this boat but I’m gonna sum everything up and hopefully this will be the last time!



First of all, this is what we’ve done to it.

• Cleaned and replaced all carburetor parts with Mikuni oem. As well as 4 new 80 gram arm springs. Set the pop off pressure as well.
• All fuel lines and oil lines were not the originals and looked very open.
• Cleaned all 4 rave valves
• Replaced all spark plugs and trimmed the wires.
• Brand new battery
• Replaced one of the solenoids that went bad. Both are working and in good condition now.

Okay so I’m going to start on a couple weeks ago when we took it to the lake. The boat was running awesome almost the whole time, both engines running at 7k rpms like they should. Until the way back to the boat ramp. It started dying and wouldn’t stay running for very long.

Just decided to bring it back home and take a look.



Got it home and nothing seemed wrong, we took the carbs apart and checked everything. Looked alright. Fine tuned the pop off pressure and re installed.



Next weekend. We took it out on the water to test it and different symptoms occurred. First, the boat ran fine at 7k rpms for maybe a minute or two until the drivers side engine died (like a loss of electrical power) Started it back up and then neither engine would go above 5k rpms.



Ran around for a little bit and then the drivers side died and wouldn’t go above 3k rpms.



Headed back to the boat ramp and then the drivers side kept dying/wouldn’t stay running for longer than 5 seconds.



We limped our way back onto the trailer.



The whole day we were testing to see if we was running lean by pulling the choke, just died every time- so it wasnt running lean. Also, throughout the day there was intermittent dying on the drivers side-like loss of power.



(I have videos of all of these symptoms except it running at 7k)



Got it back home and did some research, replaced all 4 spark plugs and trimmed all the wires down.



Decided to take it out again and see what’s up.

First, boat ran good like it usually does- 7k rpms.

Next, the drivers side engine died like a loss of power. Then neither engine would go above 5k.



We drove around for a decent amount and they stayed at about 5k unless we hit a turn or wake just perfect then maybe one engine would fire up and run 7k but not every time.



We have been and I still am thinking this is an electrical issue. The reason I believe so is because it runs good until the engine dies-like a loss of electrical power. And then it just won’t run above 5k rpms again.



But, when we did hit a wake or turn just right it would go above- which wouldn’t be electrical I would think. But who knows.



Any help is greatly appreciated. Sorry this thread is so long! Lol



Thanks!

 

[Dr Honda]

Sounds like the fuel system is lightly plugged up... or the engines are overheating. By any chance, did you pull the choke to see if the RPM's would jump back up?

Regardless... when you have issues like this... check the compression to make sure there isn't damage.

 

[CadeZ]

Yes I did pull the choke. Everytime I’ve pulled it, the engines just die. So that would mean it’s not running lean?
Second, there are overheat sensors on each motor- it runs the same whether they are plugged in or not.
The compression checked out in specs for all 4 cylinders. I can’t remember the exact psi but they were all above 130.

 

[Dr Honda]

Yes... pull the choke... dies.... it is not lean. So that rules out the plugged fuel system. (since it will restart and run after it sits)


The over temp sensors on that boat have nothing to do with putting it into a limp mode. BUT... if the engines are actually overheating... they get tight, and start to loose power. SO... you should make sure they sensors are working, and that the buzzer in the helm works. So... take the wire off the sensor, and ground it. listen for a constant beep. To test the sender, hook it to a meter. It should be open. then, put it into a pot of boiling water, and it should go closed. It's just a thermal switch, and they are known to go bad. Not to mention, they can build corrosion, and simply loose their ground. ( It closes around 200 degrees F) But, be carful. They are brass, and the body is thin, with a pipe tapper. When putting them back in... do not over tighten them. I've seen way too many of them snapped off in the head shell.


Since you don't know your compression numbers, I'll assume that it's old numbers, and you aren't doing what I'm looking for. If there is an overheating issue... there could be new damage. I'm looking for current numbers... not a test that was run before. The main reason I'm asking for new numbers is... if there is damage... we will then know why it's not running right, and won't chase our tails looking for any other issues. If you think about it... it would be like you going to the doctor when you are not well... and saying... "I took my temp last week so I can't be sick."

 

[Sandman251]

Check your battery voltages. I had a Speedster that acted up like this and it ended up being a rectifier. Real Gremlin type stuff. Cutting In & Out, and low WOT RPMs. The system requires a minimum voltage to run properly. if your rectifier is not returning voltage to the battery the battery will discharge and can cause problems like this. You should be seeing at least
14 volts at the battery when the RPMs are over 4K.

 

[CadeZ]

Okay so we took in consideration of all your guys help.

We checked compression just to make sure - Passenger side was 140 psi, Drivers side was 150 psi

Within a couple psi of each other on each engine.



Second, I researched some more and really came to the conclusion that it was the rectifiers, or atleast that was one of the problems.



So we ordered 2 new ones and installed them.



We took the boat out today and the symptoms were-



Before getting out of the no wake zone, the drivers side engine died (like loss of power)



But then. We floored it and they were “stuck” at 5k rpms. UNTIL the boat planed out across the water and became level. Then they both roared up and went to 6.5k rpms or so.



The rest of the day on the water the engine never died (like loss of power). And it would always rev up to 5k until planed out on the water and then it would run awesome



Not sure if this is carb settings or what?
Pop off pressure psi set too high?

I know that both engines are running a little on the richer side just from looking at the spark plugs.



I have a video of the boat running like it did today as well.



Thanks for your help! And any suggestions are greatly appreciated. Thank you.

 

[Dr Honda]

Since it dies when the choke was pulled for a second... I would say you are rich. It could be from a low pop-off... but you could also try to close the high screws just a little. (1/8th of a turn)

 

[Tudorc]

I have similar issues with a single engine 97 Challenger. Have you had any luck?

 

[CadeZ]

Okay, so we took the boat out again. It ran pretty good for the most part (same symptoms as last time)



But, we now noticed a bog in the drivers side engine. After it has been ran for a decent amount of time, shut off for a little, and started back up. It has a bog at about 3k that will kill the engine. The only way to get around it is to let the engine run for a while before giving it more gas.

The bog is only there after it has been ran, shut off, and then started again.



So out next option is to take off the carbs again and adjust pop off pressure to maybe a higher psi?



Oh. And we adjusted the high speed adjustment screw from 1/2 to 1/4 to 0 and it didn’t seem to help or change anything.



Any other things we should look for or change? Thanks.

 

[Dr Honda]

Nope. At this point... remove the carbs, make sure they are 100% clean inside, and that all the parts are OEM... and that they are the correct parts. Set them exactly to OEM spec... and it will run.

Oh... I guess there is one thing else to check... make sure the return hose isn't clogged.

 

[CadeZ]

Okay, we have removed the carbs several times for adjustment and what not (I think 3 or 4 to be exact)
We rebuilt everything with oem and replaced the arm spring with an oem 80 gram as well. Not sure what else to change other than the pop off pressure. Which to my knowledge stock is around 24-43 psi or around there. And all 4 carbs are in that range.
Another forum member noted that I didn’t have accelerator pumps on my carbs. Could that be a problem?

 

[Dr Honda]

Nope. The accelerator pumps are a pain in the butt, and aren't needed with a 800 or smaller Rotax engine. When my shop was open... any time a toy would come in with accelerator pumps that weren't working... I would just remove them. (and normally re-jet the pilot jet)

There are several very small ports in the carb. Make sure they are perfectly clean. Most of the time, when I would get carbs to clean... 2 of the 3 "Bypass" ports would be plugged up. Also.. with the bog issue... it's a sign of pop-off that is high, or a high speed check valve that is leaking back. (carb runs out of fuel when vacuum is in transient between idle and high circuits)

With your comment about pop-off.... did you actually check it? Or did you just put the recommended spring in?

 

[Dr Honda]

One last thing...... Do you have the factory air boxes on the engine?

 

[CadeZ]

Okay. But yes we flushed wd-40 through the by pass ports and they were not plugged. Second, yes we did check the pop off. We set all of them around 30-32 psi.

Yes I do have the stock air boxes installed.

My other question I’m confused out. You mentioned that a high or low pop off pressure could cause this? Which one- high or low? Thank you.

Second, we replaced all the check valves along with the rubber grommets.

I don’t believe the pilot jet is rejetted for not having the accelerator pumps. The previous owner took them off and he had aftermarket carb parts in.

So would that cause this? The passenger carb is working fine with the pilot jet that is in.

Thanks for your help.

 

[Dr Honda]

Um...... why WD40? I would be using carb cleaner, and compressed air to verify. I guess it's a mild solvent. (just curious)

OK... we may have found your issue. If the pumps were removed... and it wasn't re-jetted to add the mid fuel needed to transition... then it would have a mid bog.

I just want to verify... you have 800 engines, with twin 40 mikunis... right? (2 on each engine)

 

[CadeZ]

WD-40 because that is what was suggested to perform the pop off pressure test. Just decided to use it to make sure the airways were open.
Second, yes, I don’t believe it was rejetted-maybe it was idk. But what’s pilot jet should I order? Where to order?

Yes I have twin 787 engines. I was told I had stock carbs on a post thread that I sent a picture in. Here’s a picture.

So pilot jet needs to be rejetted to what size approx.?

Pop off pressure could be too low or too high?

Thanks for you help.

 

[Dr Honda]

Without the accell pump... I would put in a 70 pilot, and probably set the low needles around 1 to 1-1/4.

 

[CadeZ]

Okay so I haven’t been in town the past week so I’ve just been researching and thinking. I believe I will change out the jets.
But, I have read many posts on here about the raves not opening up, or opening late. I cleaned all 4 and they all seemed okay with the slots in them. But, I had no idea they even had adjustments. So I cannot tell if they are out of adjustment.

Would the RAVE’s be causing this? Maybe not opening up/ or opening at the right time?
Thanks again.

 

[CadeZ]

Does anyone have any info on the RAVE’s? Adjustments? If this could be the issue as well?
Thanks

 

[Dr Honda]

Nope... RAVE valves don't change peak RPM much, it just shifts the HP curve. If they hang open... you lose torque in the lower RPM's... and if they don't open you lose upper "Punch".

 

[CadeZ]

It’s not that the boat isn’t hitting peak rpms at 7k. It’s that there’s a hesitation before it gets on plane. Do you think that the raves are not shifting the HP curve early or late enough? I’ve been seeing so many posts about these boats having these rpm problems. With only one posting a solution, which was adjusting the rave valves. Which I have adjusted all the way down through all the way up. Which didn’t help.

And I’ve been thinking about the pilot jet being a wrong size. If it was the wrong size, then wouldn’t it never let the engines get above 5k? And it wouldn’t cause a “hang up” in the rpms? It’s not that it can’t get up to 7k. It’s that there’s a good hesitation before it gets on plane. To me, that doesn’t sound like a wrong pilot jet-but what do I know. These boats have put me through my ropes. I’ve messed with this and researched for so long I’m about to sink it!
Anyways, thanks for all your help. Any suggestions?

 

[GilDevil]

Hi Cadez

1) It seems you say that replacing the rectifier with a new one improves your RPM, that it allows you to reach 7000, is that right ?

2) Looking back at your Jun 8 2018 # 12 post I am surprised by your fuel line, it seems fuel gets in the carbs from the rear of the boat, traveling through yellow silicon hoses and plastic Ys. My carbs are fed from the passenger seats, they don't use silicon hoses nor Ys, moreover your carbs inlets are different from mine; I have just bought a replacement carb and am struggling because the inlet is not like in my original carb, it is a simple elbow instead of a T so to recover a T I will use a Y and a very flexible hose, maybe a silicon one ... so maybe some of or all your carbs are not original ones ... and fuel doesn't flow in steadily or with the pressure expected by the factory setting ... this is something I am afraid of for my future own fix ...

 

[CadeZ]

Well yes and no. Replacing the rectifier did allow it to go above 7,000 rpms. BUT, only sometimes and only after the boat gets on plane.

Second, I am sure my carbs are the originals, except for the oil injection is blocked off and the accelerator pumps were removed. But I know the fuel lines are not original. And I know the last owner was the one who replaced those. But this boat has ran almost perfect with those exact fuel lines and nothing has changed.

 

[GilDevil]

Thanks for clarifying about the rectifier

Do you confirm your fuel hoses turn around the carbs block and enter it from the rear of the boat ? How long are these 2 extra loops ? 0.5 m < < 1m ? Confirm also that they are silicon made ? That the Ys are plastic made ?

Maybe a too long U loop, a slight squeeze in the aging silicon turn and cracks in the aging plastic Ys cause a weak feed. This circuit is not the factory setting, I believe. The 20 years old fuel pump could also be not powerful enough to efficiently push the fuel through the loop, a job it was not supposed to do originally.

Concerning my own problem I suppose it comes from a high speed screw that is seized, "sealed" to the carb, I cannot move it at all, and after reading the shop manual I believe the screw is way too open, which could explain why my engine is capped at 5000 while consuming much more than the other engine running at 6500.

 

[CadeZ]

Well no I haven’t confirmed your questions about the fuel lines. I haven’t messed with it since. But, I know it was all working correctly a month ago and there was no problem at all. So I doubt the routing of the lines is the problem. Plus, I know it’s getting gas because if I pull the choke out when it’s “stuck” at 5k. The motor instantly dies. So it’s definitely getting enough gas.
Second, on your problem. The high speed screw could cause your problem, it definitely isn’t mine. You can take yours high speed screw out without even taking the carbs off to check if it’s stuck. Mine was not stuck and we put brand new o rings on all 4 of them when I did the carb rebuilds.