2007 Challenger 180SE only going 1/2 speed?

[Oldie]

Had an interesting thing start happening with my boat. I purchased it last year, and everything ran great. Boat would go 40+ mph at top engine speed (6000-6100rpm). On the last day using the boat last year, my son the engine made a wierd sound for about 30sec, and then everything seemed fine, although the engine sounded different (He didn't actually let me know this until just recently, sigh).

Anyway, had the boat serviced earlier this year. They did the standard maintenance and had to replace the bilge pump, but said the rest checked out fine. We just put it in the water for the first time this week, and something is definately wrong... the boat won't go much past 20mph, even at top engine RPM. The engine runs fine, at least it appears to (starts right up, gets to top rpm quick as always, etc.). He didn't remember hitting anything or getting anything sucked into the grates, and the lake where we take it is clear of most debree, but I'm not really sure what the problem could be.

The boat only has 48 hours on it, could the supercharger have gone? No idea what else could be causing the low top-end speed.

Thanks
Mark

 

[Pirana]

Does the engine revs up fast (like a slipping clutch on a manual car)? Could be the pump suffering from cavitation. The impeller and the wear ring clearance might be too much either by sucking debris into the pump or too much wear in the ring. If thats the problem then simply replacing the wear ring and possibly the impeller will fix the problem.

 

[Oldie]

Thanks for the reply. I'm not even sure how I would check that. The engine revs quick but no different (at least that I can remember) from before this started.

 

[Steve_Cay]

If the engine runs properly throughout the whole RPM range, reaches max RPM, and revs quickly but the boat does not move as it did before (feeling like it suddenly goes into neutral after a certain speed), chances are the engine is ok ... but you are not getting sufficient bite into the water to pump it through: hence cavitation as Pirana states.

Once easy thing you can check (if you did not already) is get under the boat with a flashlight and check into the intake grates all the way to the impeller. Anything crap in there? Does the impeller look all banged up?

 

[pvamax]

Boat would go 40+ mph at top engine speed (6000-6100rpm).

Do you mean 8000-8100, or is it really only seeing 6000? If you are seeing only 6000 this year, your supercharger is done. That is about all the rpm they will produce when not working.

 

[chlarson23]

My super dumped the needle bearings last year and when it happened there was a very distinct sound like almost hitting a window with a hammer and having it shatter. After the initial epic fail it sounded like it was running fine although i knew that it wasn't. You could always check you’re super to eliminate that also.

Just pull the large intake hose off the super and stick your hand in an attempt to turn the fan, if it free spins there is a problem. If you can't spin it, you should be ok.

Also I attached some pics of my wear ring and impeller from when I bought my boat. If it looks anything like that you need to replace them both.

 

[Oldie]

Thanks for the replies. I haven't had much time to work on it, I'm going to pull it out of the water this weekend and check.

To pvamax, I don't ever remember it getting anything over 6k, although that could be my poor memory (i'm not getting younger). The other interesting thing about this boat is I'm not actually sure if it's a 2007 or a 2006 model. It has the dash of a 2007 (the all-digital small binocular looking gauges), the manual is a 2007, but the boat was registered and listed as a 2006.