New to jet boats. Bought an 08 180SE with 30 hours. Fun boat but just used it for water skiing and not that impressed. With my old I/O I just put the throttle down and go. When I put the throttle down now it goes to 8K RPM but it is like "spinning its wheels" and not going anywhere. If I feather the throttle there isn't the issue but water skiers do not appreciate the slow pickup. Something wrong with the boat or my technique? Remedies??
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Water Skiing with Challenger 180 issue
- Thread starter steveo3
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You have a cavitation issue.
One of three places to look.
1). Something wrapped around the impeller if the drive shaft. But I doubt this is your issue as you didn't mention a vibration
2). Wear ring concern. The gap from the impeller to the ring should be NO MORE than the width if a dime.
3). Bad carbon seal / boot issue. It sucks air from inside the hull and puts air right where the impeller is.
I'm betting number 3 is the issue.
You can place two wire ties around the bellow and tighten them a but. This puts additional pressure against the carbon seal. If nothing else this is a great test to do. If it works you know what your winter project is. Replace the seal and all of it components.
One of three places to look.
1). Something wrapped around the impeller if the drive shaft. But I doubt this is your issue as you didn't mention a vibration
2). Wear ring concern. The gap from the impeller to the ring should be NO MORE than the width if a dime.
3). Bad carbon seal / boot issue. It sucks air from inside the hull and puts air right where the impeller is.
I'm betting number 3 is the issue.
You can place two wire ties around the bellow and tighten them a but. This puts additional pressure against the carbon seal. If nothing else this is a great test to do. If it works you know what your winter project is. Replace the seal and all of it components.
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Thanks for the info. Good to know there are solutions.While searching through the internet I found some postings where people say that cavitation is a problem in these boats and you cant do much about it.While new to jet boats I generally do my own maintenance/minor repairs. Where can I get a service manual to guide me through procedures like the ones mentioned above?
Did a visual inspection today. To my inexperienced eye the impeller looks fine. Fit is close to the outer ring and it looks like the outer part of the impeller is actually slightly touching the ring and has made a light scratch on it. There are a few strands of grass between the impeller and ring but I assume that is a common occurrence. As far as the carbon seal I am not sure how to check . If I loosen the bellows and check that area will I be able to visually indicate an issue?
If you are seeing grass in there I would suggest taking a better look. You may have stuff wrapped around the shaft/impeller. If so, that is all it takes fro cavitation...
Update-brought into dealer. After tear down it looks like a carbon seal issue as Coastie Joe predicted. They hooked up a computer and the only code was overheated exhaust at idle which probably goes along with the carbon seal issue. The mechanic said running out of water too long can destroy the seal. Four days for parts to arrive.
It literally sucks air right out if the hull and feeds the impeller air.
Since we are not working with planes, air and impellers don't mix.
I think they are on the right track.
Let us know,,,?
Boat is back from the shop. Carbon seal turned out to be OK. The pump seal had a tear 1/2 way through and the bolts were loose. Tried it out and still a major cavitation issue if you hit the throttle hard. A bit better when moderately accelerating. $200 to take apart and replace the seal and one small O ring which I figure is reasonable. Probably will try a new impeller next season to see if it reduces cavitation.
Sportster-2001-951C-Stock
Well-Known Member
Yes, and there are some subtle differences between cavitation and ventilation:
"As a shape passes through water at an increasing speed, the pressure that holds the water to the sides and back of the shape is lowered. Depending upon water temperature, when the pressure reaches a sufficiently low level, boiling (the formation of water vapor) will begin, The collapsing action, or implosion, of the bubbles releases energy that chips away at the blades, causing "cavitation burn" or erosion of the metal.
The initial cause of the low pressure may be nicks in the leading edge of the impeller resulting from debris passing through. Massive cavitation by itself is rare, and it is usually caused by an impeller that is severely bent or has had its blade tips broken off resulting in an impeller far too small in diameter for the engine.
Ventilation, often mistaken for cavitation, occurs when air from the water's surface or gases from the exhaust outlet are drawn into the impeller blades through the jet intake. The normal water load is reduced and the impeller over-revs, losing much of its thrust. This action most often occurs when turning, particularly in conventional aluminum jet boat hulls (not using a reverse chine). Ventilation can also be caused by aerated water from extruded chine hulls and simulated reverse chines by welding 1?x3? angles along extrusions. Thunder Jet's Exclusive Reverse Chine Hull allows for less impeller ventilation than these conventional hulls."
http://www.thunderjet.com/thunderjet_us_frequently_asked_questions.html
We of course aren't running aluminum hulls, this passage attempts to plug the benefits of a manufacturers hull design unfortunately confuses the issue somewhat so try to read between the lines on that if you don't mind...
"As a shape passes through water at an increasing speed, the pressure that holds the water to the sides and back of the shape is lowered. Depending upon water temperature, when the pressure reaches a sufficiently low level, boiling (the formation of water vapor) will begin, The collapsing action, or implosion, of the bubbles releases energy that chips away at the blades, causing "cavitation burn" or erosion of the metal.
The initial cause of the low pressure may be nicks in the leading edge of the impeller resulting from debris passing through. Massive cavitation by itself is rare, and it is usually caused by an impeller that is severely bent or has had its blade tips broken off resulting in an impeller far too small in diameter for the engine.
Ventilation, often mistaken for cavitation, occurs when air from the water's surface or gases from the exhaust outlet are drawn into the impeller blades through the jet intake. The normal water load is reduced and the impeller over-revs, losing much of its thrust. This action most often occurs when turning, particularly in conventional aluminum jet boat hulls (not using a reverse chine). Ventilation can also be caused by aerated water from extruded chine hulls and simulated reverse chines by welding 1?x3? angles along extrusions. Thunder Jet's Exclusive Reverse Chine Hull allows for less impeller ventilation than these conventional hulls."
http://www.thunderjet.com/thunderjet_us_frequently_asked_questions.html
We of course aren't running aluminum hulls, this passage attempts to plug the benefits of a manufacturers hull design unfortunately confuses the issue somewhat so try to read between the lines on that if you don't mind...
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Not sure whether it is ventilation or cavitation but for sure it is annoying to have the the reving without the power. There is a great deal of discussion on the internet about this issue and Challenger 180's. Others , however,have said they can slam the throttle down and have no issues. I did notice that the wake behind the boat has more of a "rooster tail" since getting it back from the shop??
Sportster-2001-951C-Stock
Well-Known Member
I also have this issue with my Sportster, but I slalom and that's the one I think is most demanding. Heck, I can even make a sterndrive work if I try, by leaning back and making it pull me up but the stermdrive always wins, where I can accidentally give this seadoo a hernia and I can't lean back and just let the boat do the work like it should be. I think it's actually cavitating because it seems like steam and I don't think it's hitting the rev limiter but I'm still working with my driver to try figuring it out and she's not really helping much.
It all started once I got the engine running right, and the prop does have small nicks in it, but I have doubts my hole shot will improve with a better one, more like the driver will have to go slow into the throttle, which does work but you're right, it dragging the skier but it's the only way I've found, it's barely enough for me on my single O'Brien that I've skied for ages behind all kinds of boats.
And I agree with you, a sterndrive beats the snot out of these boats with the toy impeller(mine's 155mm, single screw)
It's just barely enough to get me up, and the driver actually has to have some skill, not to just nail it like it should be.
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