challenger wont pass 30mph

[cadsii]

ok so i've been working on this boat for quite a bit, go her out on the water this weekend but still cant make her pass 30mph,

takes about 20 seconds to get to 15mph then it will plane and go upto 30mph but still nothing past that, with 1,2 or 3 people...

any idea ?

also my rpms are showing as 10000rpm at full throttle...

 

[kustomkarl]

It sounds like the wear ring in the jet pump is bad, and needs replacement. If the gap between the impeller and the wearing is larger than say a piece of paper it will need replacement. If the space is too large it causes no enough thrust from the jet pump.

Karl

 

[cadsii]

thanks any quick way i can check that to confirm ?

 

[kustomkarl]

Use a feeler Guage and check the clearance of the impeller and the wear ring from the nozzle opening. Check the clearance in the middle of the blade. It should be .40 or less.

Karl

 

[cadsii]

finally stopped raining today i might have a chance to do it, i looked in the back and saw like no gap at all between, i will take some pics today, im suppose to look from the back correct ?

 

[cadsii]

ok so i changed the bumpers on the driveshaft, changed the wear ring, resleaed the pump, changed the oil in the pump, changed the plugs and wires. changed exhause coupler, took her out on the water and was able to barely pull it upto 40mph by myself, better take off then before but still not what it should be, i noticed still i have a leak in my hull. So finally sitting in the engine bay while my buddy gives it around the lake i notice that at full throttle i have a leak from what appears to be my head.

i took off the valve cover to notice where the leak was coming from, its cracked around the head.

here are some pics, i still have 150psi compression on the cylinders, anyway i could fix this without replacing the motor ? will JB weld work? i know there is not as much pressure as in the cylinders... or coiuld i have it welded ? or do they sell just that part of the head ?

 

[cadsii]

i am guessing this is from the dumb ass running it his driveway without water, the crack is 1" deep, and is on the cooling chamber around the cylinder...

 

[glenwhitt]

10000rpm at full throttle...

wow! 10K really?

 

[cadsii]

wow! 10K really?

yea i think the rpm gauge is fked up ... its showing 6-7k right away so as i start moving with a little throttle

 

[pincusa]

Well, I wouldn't say that the JB Weld would be ideal, but it might be a cheap enough fix to try. You got nothing to lose since that cylinder is toast.

I'd take a small grinder and cut a V groove into the crack to give the JB Weld someplace to bond to and fill. The cooling system is low pressure, but the thermal expansion might be what keeps the fix from working.

How did the jet pump look? This leak shouldn't be what's keeping the boat from not going above 30MPH. It sounds more like a pump issue

 

[cadsii]

pump looked great, checked all bearings, everything nice and stiff with no play, changed gear oil with syntethic 75grade, new wear ring installed, why else would i be not able to pass 35mph

 

[cadsii]

guessing this is what i need ?

link

 

[pincusa]

Yeah, a new cylinder would be the right way to go. And while you're in there, replace the rings and hone them before installing them. Personally, since I'm cheap, I'd try the JBWeld first. It very well could work.

But like I said, this isn't why the boat isn't going over 30MPH if you're making 150PSI in both cylinders. I'd look at your tach and wonder if your engine is really reving all the way up to full throttle. It could be that you're only getting 4K RPM (delta between 6K idle and 10K WOT) which would put my boat somewhere around 30MPH just as it's working on the plane.
Are you really getting WOT? Are the butterflies going straight when you push it all the way open?

 

[cadsii]

yes they are opening all the way, i do notice that on the last 20% of the throttle it makes like no difference, at the last part to full throttle, i do see the butterflies moving so i dunno.

i am cheap too so i will try jbweld first, will make videos tomorrow when i take it out again

 

[glenwhitt]

tach screwed up

With the tach screwed up it will be hard to base anything off of that. You may want to get a Tiny Tach. I have one and it gives me an hour meter also. They are pretty nice.

You may just have to go by ear. With it only going 30 but, the rrpm being up, then I would say something with the pump/impeller/wear ring/seal, etc... is the problem.

Maybe the reason you get nothing on the last 20% of throttle is because its bumbing the rev limiter. Pretty easy to do when the pump is not creating any force.

 

[cadsii]

that would make sense. but i sealed the pump with the right stuff, changed the wear ring, and made sure the carbon ring and ring carrier are aligned right, still feels like its cavitating when i give it WOT from start. i checked the impeller when i had it out had a couple nicks nothing major, i filled them down, its a staktrak 17/22 ? is this the stock impeller?

 

[cadsii]

well i am going to JB weld the cylinder today and then take it out tomorrow to see how it does, still dont know why i cant pass 30-35MPH

inspected pump,
changed wear ring
changed pump oil
resealed pump with right stuff
changed both driveshaft bumpers
changed resonator 2" 75mm couple as mine has a hole in it
changed spark plugs
cut wires down
charged battery fully
cleaned all connectors

 

[Dr Honda]

If you can find someone local to you with a TIG welder…. You could have the cylinder welded, and save it.

As far as the impeller… no a scat-trak is not a stock part. The stock part will say Sea-Doo right on it. But as I recall… a 17/22 is probably more prop than that boat will like. The high pitch may be causing your cavitation and speed problems, although… once up to speed, the extra velocity should help, but even with a modified motor… you can only get so much water out the pump nozzle, and the housing will only take so much pressure.

 

[Dr Honda]

Just checked Skat-Trak’s web site… a 17/22 is the recommended “Speed” prop for your boat. So you should be OK there. Just for an FYI… the 14.5/22.5 swirl is the recommended bottom end prop. (for acceleration)

Just looking over your list… did you change your carbon seal? Mine looked good… but once it was out, I could see that one edge was warn from the inside, leaving a very small sealing surface. Also… the boot on my carbon seal had gotten soft, and wasn’t keeping enough pressure on it to seal it properly. A new boot, seal, and stainless ring may take care of your prob.

 

[cadsii]

carbon ring looked fine, i bought another one and was able to return it since it looked identical, seems like the JB weld is holding up great no leaks that i can see right now, still cant break 35MPH,

dunno what else it could be, seems like its still cavitating at take off.

would you recommend resealing the ride shoe ? maybe air getting in there allowing it to cavitate ?

 

[cadsii]

really banging my head agains the wall here,

someone can you explain the carbon ring / ring carrier alignment to me..

the ring carrier spins with the drive shaft correct? and this presses against the carbon ring by suction from the jetpump correct? there is nothing between the carbon ring and ring carrier correct?

 

[Dr Honda]

really banging my head agains the wall here,

someone can you explain the carbon ring / ring carrier alignment to me..

the ring carrier spins with the drive shaft correct? and this presses against the carbon ring by suction from the jetpump correct? there is nothing between the carbon ring and ring carrier correct?

Almost…

The stainless steel ring spins with the drive shaft. The carbon ring is held onto the stainless ring with pressure from the rubber boot. If the either of the rings are warn, or the boot is getting soft… the suction from the pump will pull air past the carbon ring, causing your cavitation problem. And finally… no, there is nothing between the carbon and stainless ring, other than a thin film of water to keep it cool.

 

[vilord]

really banging my head agains the wall here

I thought of something reading through your thread... what if the MPEM thinks it is revving that fast too?
I know that when in neutral it has a rev limiter of 3500rpm, what is the limiter for WOT in forward?

A little cavitation at launch is normal, but it should plane in about 4 to 6 seconds.

I would suggest resealing the ride shoe, air can get in there. There was a post a while back from a dude who did that to his, and from what I remember it cut his launch/plane time in half.

 

[GemRock]

Had a very similar problem - cavitation at speeds up to 25 mph with a top speed of 30 mph. Had propulsion components checked - all good. Eventually found it was the cables leading to the reverse gate ... seems these had stretched and were not lifting the gate fully when in forward - led to the apparent 'cavitation' and the loss of speed. Had the cables adjusted today, now hitting 46 mph in choppy water.

Any chance this could be your problem too?