97 Challenger - A Couple of Questions

[Biffitis]

Hi all.

Recently purchased a 97 Challenger (single engine) and after a little work on the RAVE Valves it's running nicely. However, I don't seem to have the top speed that most are getting or that the spec's claim I should be able to achieve. On a calm freshwater lake full-out I can only get about 65-70 KPH (42 MPH) on my GPS. Won't go much over about 6200 RPM.

What should the RPM top out at? Engine runs strong so I'm wondering if cavitation caused by a worn wear ring could account for this?

Also, should water in the passenger area be allowed to drain into the center (hull) well? There's a seal there but I'm not sure if that should actually be keeping the water out completely.

 

[Seadoobuddy]

I'm not a jet boat guy but a worn wear ring will play havoc with top speed in boats and skis. What's the condition of your ring/impeller?

I would think the the center hull will drain into the bilge to be sucked out by the balers or pump. Wait for more correct answers to this question.

 

[Biffitis]

Any water that drains into the hull well will run back and end up being expelled by the bilge. But, should water be running in around the hull well door in the first place? If the boat is left out in heavy rain the bilge would be working constantly to keep up with the water entering the center well. I would have thought (and correct me if I'm wrong) that the water should run back and exit the passenger area through the scupper valve drain.

I'm not sure what kind of shape the ring/impeller are in. It's pretty difficult to get a good view up there. I'm going to pull the jet drive apart this fall/winter to service the oil so I'll have a closer look then.
Just wondering if cavitation would; a) affect the top speed b) prevent the engine from reaching top RPM.

 

[John in Valley Forge]

The lip around my ski locker hatch always collects water and dirt too. I find it annoying. Water in the locker is no big deal. When I am in the driveway at home, I will lower the front of the trailer as low as it goes to get all the water to drain forward out of the hatch (I dont know why they do not have a drain hole at the lowest point like in the other storage areas). Then raise it up as high as I can to let is all drain out the back.

As far as speed, you probably may hear from some other owners that have your model, but you may well be getting as much out of it as it gives. The twin 717s in my Sportster 1800 max out at 38mph with RPMs somewhere between 6,000 and 7,000. I just read a review from a 1997 boat magazine that indicated a Challenger 1800 (with twin 787s) topped out at 48.7mph.

I think measuring the wear ring clearance is a good idea to check.

 

[LSaupe]

Your speed sounds about right, maybe a touch low. I do mid 40's at 6800 RPM with the same rig.

I had a bad wear ring as well a while back. It manifested itself mostly with a bad hole shot and mid range perf. I was still able to make RPM's even with a bad ring. Top speed wasnt too bad except when the boat had a full load of people, at that point the boat could barely stay on plane.

Could be a faulty tach and well as throttle plates not fully open. When I got mine they would only open 3/4 of the way at the full throttle lever position.

Other key items to look at are exhaust leaks, especially at the large pipe clamp mid way down the expansion chamber and also the seal between the exhaust header, white "Y" pipe and the purple inlet of the exhaust pipe. I had low and wandering RPM at full throttle until I got both of these areas sealed up. Both places were also dumping water into the bildge (warm water). Watch both areas while under way.

 

[LSaupe]

Your pasicatedsenger area will (should) drain from the hole beneath the driver out through dedicated tubing to a scupper.

 

[Biffitis]

Alright, so somewhere between 6-7K RPM is about norm. So I'm only missing a few rev's if any. It is going WOT (wide open throttle) as I checked this after adjusting the slack out of the throttle cable. Exhaust is sound front to back. No signs of black, fumes or water leaking.

I suspect that there is some cavitation happening since the "hole shot" isn't quite as strong as I think it should be. Engine RPM climbs right away but the vessel is a little sluggish to get up and go. Back to the wear ring, and possibly the carbon ring pulling air in?

Since there's a seal around the hull well hatch I'm going to assume that it should be keeping the water out, forcing any collected water rearward to drain out the scupper, not into the engine well for the bilge to deal with. I might try adding some closed-cell foam around the hatch to see if that helps with sealing.

Appreciate the feedback. More input is always welcome...

 

[RFoster130]

It took me till now in this thread to figure out what you meant about the water issue. The ski locker im guessing is what you are talking about. Any water that makes it into there will just dump into the bilge area and into the engine compartment. It will be picked up by the pump or drained when you pull the plugs.

 

[Biffitis]

Ok. I guess you seasoned Seadoo guys call it a ski locker.
I realize that any water that gets in will run back and the bilge will pump it out. But, that's my point - if it rains for a week that bilge is going to be working O/T and would likely run the battery down, no? Is the seal around the hatch not supposed to keep the water from getting in there in the first place? Any accumulated deck water should drain through the scupper valve, not the ski locker/bilge. If I'm out of sorts please enlighten me. It's knowledge I crave... :coolgleam:

 

[LSaupe]

Dont forget to check your engine compression numbers. Should be around 150.

 

[bigJake]

Any water that drains into the hull well will run back and end up being expelled by the bilge. But, should water be running in around the hull well door in the first place? If the boat is left out in heavy rain the bilge would be working constantly to keep up with the water entering the center well. I would have thought (and correct me if I'm wrong) that the water should run back and exit the passenger area through the scupper valve drain.

I'm not sure what kind of shape the ring/impeller are in. It's pretty difficult to get a good view up there. I'm going to pull the jet drive apart this fall/winter to service the oil so I'll have a closer look then.
Just wondering if cavitation would; a) affect the top speed b) prevent the engine from reaching top RPM.

cavitation will affect speed but not rpm, you would just get high rpm without gaining speed

 

[Cid6.7]

If your boat sits for any period of time when raining just pull the plug water will drain out it instead of the bilge pump having to pick it up..(on the trailer of course)

Water going from cabin "should" drain out the scupper valve but any water that goes into the ski locker will drain out the bilge while running the boat or sitting in the lake or out the drain hole when towing/storage..

I leave my plug out any time the boat is not in the water..

 

[RFoster130]

Ok. I guess you seasoned Seadoo guys call it a ski locker.
I realize that any water that gets in will run back and the bilge will pump it out. But, that's my point - if it rains for a week that bilge is going to be working O/T and would likely run the battery down, no? Is the seal around the hatch not supposed to keep the water from getting in there in the first place? Any accumulated deck water should drain through the scupper valve, not the ski locker/bilge. If I'm out of sorts please enlighten me. It's knowledge I crave... :coolgleam:

It shouldnt be a problem. If its parked somewhere on land leave the plug out and all the water drains. If you have it on the water, that is a whole separate problem. These boats are not built to be left in water for long periods. The ski locker does have a seal around it, it might leak but you really shouldnt be getting that much water from the passenger area down into the bilge area.

 

[John in Valley Forge]

Ok. I guess you seasoned Seadoo guys call it a ski locker.

Or a Weapons Locker if I got the 12 gauge.

 

[cjb1985]

I think you'll find the hole shot speed on these boats is never what anyone expects.
Whilst it sounds like your top speed is about spot on.

The fact that the Jet pump needs to load with pressure and water causes a delay off the mark.
If I had 4 heavish guys in the boat, would struggle to get on the plane without shifting some weight forward or take a fair amount of time.

Best investment ever is an impeller upgrade.
Skat trak swirl shouldn't sacrifice much, if any top end. But my time to get out of the hole/on the plane I would say is better than halved.
I've never timed it, but substantially improved to the point you notice.
Also carrying loads seems to have less of an effect.