Impeller, maybe?

[crmsnrider]

I've had good luck all summer with my challenger(after correcting a few carb issues in the spring). But something strange happened today. It started to accel very slowly(like 20 seconds to 15 mph @ 7000rpm). Then it would accel very quickly(like normal). Then very slowly again. The left motor seems to be the problem(again). Could it be a coolant system prob? Wear ring jamming the impeller? Impeller drive mechanism slipping? All of the above? Is there something I could take apart and clean? The motors rev up and sound strong, just lost its 'get up and go'. I'm a dummy with this sort of stuff so please use simple vocab.

For the record, I'm very careful to not suck up sand, grass, etc..

Thanks

ps. How much would i expect to spend if I have to replace the impeller/wear ring? Should I just do 'em both if only one needs it?

Sorry for all the question marks

 

[kustomkarl]

I would replace the spark plugs first, and gap them properly. It sounds like a fouled plug. Use NGK BR8ES Gaped to .021"-.024"

Karl

 

[crmsnrider]

Plugs are a couple months old. I can replace them, but would bad plugs cause the boat to go nowhere while revving to 7500? I'm confused.

 

[timmyboy76]

recheck the intake grate, for obstructin. Then if nuth'n there, check the clearance onthe wear rring..:cheers:

 

[kustomkarl]

Maybe I misunderstood your post...is it poor erratic performance, or is it just getting to top rpm's is the problem all the time?

 

[crmsnrider]

Sometimes, as in this past weekend, never before. We got out to the lake and it cranked right up. Accelleration was normal and everything went fine for an hour or so. I shut the motors down and floated around a bit. When I cranked back up and got ready to go, the boat wouldn't go anywhere. As if the impeller(port side) either was not sucking up water or just not spinning. Eventually I shut the motor down and floated a bit while I checked for anything obviously out of place around the motor. I cranked back up and everything went fine for a minute. After a few laps it suddenly slowed to a crawl. Though the engines stayed at 7000-8000 rpm. We called it day at that point and crept back to the ramp.

Poster above says to check the intake grate. How do I remove it?

Sorry for the confusion as I'm new to boating and need to learn the lingo a little better.

Thanks for the replies.

 

[kustomkarl]

The intake grate is where the water enters the Jet Pump. It is possible that the Wear ring is damaged. It is plastic and surrounds the impeller, or something might be in the jet pump assy. Give it a look to see if the space around the impeller and the wear ring is equal all around the impeller and is .040" Clearance around the impeller. It should look about as thick as a piece of paper.

It also might be a jet pump shaft problem...is it loose?

Karl

 

[crmsnrider]

Thank you. Will take a look as soon as work gives me enough of a break.

 

[seadoosnipe]

Impeller....

The impeller is always the likely source of a problem in acceleration from a stand still. Like you can push the throttles, get 7k rpm on your engine but not move anywhere.....

Well, you got one problem that kida eleminates the wearing ring. You state you can stop the motor and start it back up, increase slowly and the boat will actually run. The point, if the impeller wearing ring is shot, the performance problems are always the same. There is no sometimes it runs, sometimes it does'nt.

I think your sucking air, cavitating. When you finally push the air out of the impeller, your thrust picks back up. There is such a huge list of why this can happen. The thru hull seal, pulling air from your engine bay is a very likely source. Your impeller and stator vanes can be dinged up pretty bad, creating turbulence. If you had the pump off recently, the seal against the hull is not making full contact. I use silicone to make sure I get a good seal. I also let it dry for 24 hours before putting it out on the water.

Last, if your beginning to have problems with your drive shaft, it will begin to spin the impeller. Once you reach a certain degree of torque, the splines will begin to roll over in the hub of the PTO or impeller. Running on one motor, you might be able to hear this.

Where ever you stand, you'll need to remove the pump and go over ever possible scenerio that I've stated above. And they are not all the possibilities. There may be more...........so, let us know what you find out. Use the "manage attachments" link below to send us pix..........:cheers:

 

[crmsnrider]

I checked the intake grate and it looked clean. Took the boat out today, and it ran great. I'm not sure why it was acting funny last week. This boat has a mind of it's own and an owner that knows little (but learning fast) about boats, inboards in particular. As far as sucking air in, that could explain why it works fine most of the time but acted up that one spell. Not sure what the thru hull seal is(self explanatory I'm sure). Not sure what stator vanes are. If I wanted to get to my impellers and remove to replace with afetrmarket ones, I'm not sure how to do that. I have been considering doing that this winter b/c I'm sure it would make an improvement. 01 model, probably has originals on it.

Any suggestions on the type(pitch,thrust,brand) of impellers I should go with?

Thanks everyone for helping!!

 

[saintjon]

I have a similar problem and have spent a lot of money trying to get it fixed. My problem, when it runs, it runs great. When it runs bad, it runs real bad. Won't rev. and just boggs down. I check the inlet and no weeds. What I have noticed is when it runs bad, like steam is coming out the back. I opened the engine cover when it was running bad and noticed at the back of the engine, drive shaft I think, water was gushing in around that area. Stop it for a bit and it takes off and will run great. When it runs great, no water comes in. Any ideas?

 

[timmyboy76]

new thread..

I have a similar problem and have spent a lot of money trying to get it fixed. My problem, when it runs, it runs great. When it runs bad, it runs real bad. Won't rev. and just boggs down. I check the inlet and no weeds. What I have noticed is when it runs bad, like steam is coming out the back. I opened the engine cover when it was running bad and noticed at the back of the engine, drive shaft I think, water was gushing in around that area. Stop it for a bit and it takes off and will run great. When it runs great, no water comes in. Any ideas?

should've started a "new thread", boss...but anyway, sounds like you need a new carbon ring and accordian boot. Along with the steel collar (which you can lap on a wet/dry sandpaper), those parts are what hold back water, if bad then you'll allow water in, and the pump assy is pulling air thru the jet system and not water, causing you to go nowhere..

 

[saintjon]

Is that an expensive project?