Almost there but not quite (rpm problems)

[n7188u]

Hi Seadoo gang.

After three months of very intensive rebuilding of my '99 Challenger, I am almost there.

What seems to be the last issue with the engines in this otherwise nice boat is that when I get to about 5500 RPM on the right engine it bogs down to about 5100-5200 RPM and stays there even at full throttle. The right engine goes up to 7000+ RPM with no problem. I did notice a little bit of surging on the left engine (about 100 rpm up and down but hard to tell). Sometimes, as the boat picks up speed, the left engine RPM will slowly go up and then at times hit the higher rpms (I think about 6000-6500 rpm but could be more). But this increase is slow and only as the boat picks up speed.

As the left engine sits at the low rpms, it seems to run smooth except for the very slight surge. Another thing, when running in this state I tried pulling the choke and no rpm increase, it just bogs down further.

Things I have taken care of:

- New rave valves, housing and bellows.
- Rebuilt carbs and actually pulled them out again last week and rechecked all including pop-off. Changed main jets on both carbs to those specified in manual (145 and 142.5 I think).
- New plugs
- Swaped water regulators
- Compression on both cylinders (150)
- All new fuel lines, impulse lines to fuel pumps and fuel filters
- Rebuilt jet pumps (all bearings and seals)
- Impellers are Solas SF-CD-15/23 ), Solas recommends SD-CD-15/23 but I don't know if this is an issue).

Things I haven't done:
- Swap fuel pumps
- Check ignition timing
- Check rotary valve
- Check for seal leaks
- Is there quick way to verify enough pulsing to fuel pump?

I recently bought this boat so I have no idea what previous owner may have done to it that I don't know about.

Since the engine runs so strong and smooth up to 5500 RPM, even with throttle at full, I just don't know what else to try. My next attempt at fixing this will be swapped fuel pumps.

Any ideas?
Chris

 

[voodoo]

Sounds like you did everything I would have, with the pulse line is there a kink that may have it restricted? A way to prevent this and have it follow the original funky curl is to push a 10AWG copper wire inside, once you fold it into shape it stays there rather than get into the throttle arms.

 

[n7188u]

Thanks a lot for the reply voodoo.

What I will do this weekend is check fuel delivery. I am going to rebuild the fuel pump and take a close look at the impulse line and fuel feed lines.

Chris

 

[n7188u]

I was just told by my local Seadoo parts supplier that there is no rebuild kit for the fuel pumps in the 99 Challenger 1800.

Are these pumps serviceable and what options are out there to replace the pumps besides OEM?

Chris

 

[seadooya]

Did you rebuild the motors, or just "service" them, whats bolted to them? If "rebuilt", check the rv timing, 147/65 degrees. When read'n the thread, i'd say, swap the water regulators, cause yuoe rpm max, sounds like a bad W.R., but the bad motor, then should've performed correctly, with the known good one.

If timings right, swap out the entire muffler with w.r. assy, see what happens. Also, check the output ofthe rectifier, at the battery, while motr is run'n.

 

[n7188u]

Thanks Seadooya,

I did swap the WR but not the mufflers. Still low RPM.

I bought the boat 3 months so I really don't know the history of these engines. I didn't rebuild, just did a bunch of work to ensure things would be OK (change oil lines, rebuild carbs, removed and cleaned repainted exhaust pipes, counterbalance shaft lubrication, etc). Rave valves required a lot of attention because the threads in the valves were worn and kept destroying the plastic pistons so they all got replaced.

Is there a way to do a quick check of the RV timing to see if it is in the ballpark? For some reason I have my doubts it is the RV because the increase in RPM is very strong and smooth (no backfiring) and then it hits 5500 and you see the increase stop and drop a little. Almost as if something switched on. But if all else is exhausted I will check this too.

Chris

 

[seadooya]

yeah, wouldnt waste time with RV. Try the muffler thing, the rectifer test first, hows compression, whats the plugs look like...

 

[n7188u]

Rectifier: I tested last weekend outside of water and it was OK. Under 14. But I have to admit that at one time I placed a multimeter in the system in water and I did record over 15 at one time. Just brief. It was under 14 most of the time. However, I do own an oscilloscope so I will check to see how noisy the output is.

Compression is good (150) but that was with engine warm, not hot (hard to get the engine really warm when ran briefly outside of the water).

Plugs are a dark brown to a little dark. May be a bit rich I think but hsa are closed so I don't think I can go leaner without jet change.

I swapped the fuel pumps this afternoon. I will water test this Saturday. Will report.

Gosh, I cant wait to see this engine running good. The boat is not that bad now, but I have a feeling it will be great when I get this issue fixed

Chris

 

[n7188u]

I just wanted to provide feedback on my engine problem. I think it is a good idea to explain how the problem was solved for other members to benefit.

So I hate to admit it but the problem was not the engine (it was working fine all the time) it was one of the tachometers.

As I accelerated, the right engine would hit 7000 RPM (or so I thought) and I would not advance that throttle further while pushing the left throttle to full. Right engine would indicate 7000 RPM and left would just sit at 5500 RPM. I thought there was a problem with the left engine never reaching full RPM. The problem was that the right tach was indicating about 2000 RPM high and for some reason did not make the connection until a couple of weeks ago. In hindsight I should have noticed the right throttle was sitting half way up but it just didn't click.

I bought a TinyTach as a reference and sure enough the right tach is at fault. I now I allow the right engine to come up even past 7000 RPM indicated, which is really 2K lower, then left engine will come up nicely and both engines will reach max RPM. SWEET!!!

So after 4 months of work, I can say that my boat is all working as it should.

My next project will be to see if I can somehow fix the tach without spending a fortune.

Chris