1997 challenger stuttering off the start

[red dragon]

hello, my wife and i test drove a 97 challenger. for the most part it seemed to run fine. however i notied one issue that bothered me, and the guy who owns the boat isnt very bright and has no clue what it is. so here is my best description of what its doing and hopefully one of you can help me out befor i buy this thing and its a money pit. when you first take off and give it a good amount of throttle it stutters until right befor it planes out. now if you back off the throttle as your headed to plane it stops stuttering. as i got more comfortbale with the test drive i got it up to about 25 mph and then whipped it around hard and when the back of boat dug in it stuttered again until back on plane. its hard for me to say really if its something hitting under there, but i kinda sounds like its bouncing off a rev limiter, but it isnt at full throttle yet. i know a good bit about boats. however this is my first venture into the jet boat world so im not 100% on things yet. is this a normal thing, or is this a sign of something bad to come, or is this something easy to fix. im not a pro mechanic by any means but im good with a wrench, i do all my own maintance of my other toys and installed my own lift kit of my truck so i can possibly do some work this as well. aside from the initial stuttering it ran well, it would run about 43 mph with 3 people in the boat, turned on a dime, its just that stuttering off that start that has my bothered. thanks in advance for any information......Mark

 

[craigy]

Do a compression check,should be above 140lbs [each cylinder] on a well used engine. Also stuttering might be a lean running low speed jet.

 

[red dragon]

ok ill see if that guy can check the compression, i dont think he will tho, hes not very bright, it isnt local either its about 70 miles one way drive, so it might be a while befor im back up that way... thanks for the info...

 

[scski]

Sounds like a fuel delivery problem, possible carbs need cleaning/adjustment. Fuel valve may be clogged, etc.

If the engine is revving up and it takes a while to plane, like a car's clutch slipping, then you have cavitation. Probably the carbon seal, or impeller wear ring or both.

If you are shopping for a boat/ski, invest the 30-40 bucks in a compression gauge and test the engine yourself when you look at a boat. On a cold engine, ground the plug wires to the grounding posts, pull both plugs, throttle wide open and crank over for a few seconds until you get your highest reading. Repeat twice for each cylinder to make sure you're getting a good reading. 150 psi is healthy on the 787, anything below 140 is questionable.

When you water test the boat, see how much water is in the bilge. If it's more than an inch or two, enough to start climbing up the bilge pump, you may have a carbon seal or other leak. See if the water is hot, if so the engine may be leaking from the cooling system. Look at the jugs (cylinders) for cracks. It helps to have a small mirror to see the bottom side where they usually crack.

 

[Dr Honda]

Do a compression check,should be above 140lbs [each cylinder] on a well used engine. Also stuttering might be a lean running low speed jet.

Nooooo......


150 psi is a good engine... 135 and it's getting close to time for a rebuild. Also... a lean run wont' make a "Stuttering" sound. A rich mix can do that... but what I'm guessing is that the boat is experiencing a little cavitation. Basically... if the pump clearance is high... or there is an air leak... the pumps can't make full pressure... and you are bouncing off the rev-limiter. Most seadoo's with a little time on the pumps will do that. At this point... the damage could be minimal, or it could be huge... but with what you are describing... I'm going to say that the carbon seals are leaking a little, and under a high load (Full throttle/low speed) You are sucking air past them.

As long as you are good with your hands... it's not a big deal. Regardless... you can use that as a bargaining chip since you will have to put a little $$$ into it, to make it perfect.

 

[Dr Honda]

Before you get too crazy with worrying about the little problems... how is it cosmetically? and... how much $$$$ is it?

If the price is low... grab it. If the price is high... pass.

 

[red dragon]

He is asking 2500, im not gonna give him anymore than 2000 if that, my firtst offer will be 1500 and after that ill probley walk away. Its ok cosmeticly. The seats need work but its not a huge deal, the graphics are faded but ill peel them off and just leave it white

 

[carl1269]

I think the "shuddering you are describing is the jet impeller cavitaiing. Try "sneaking" up on to a plane rather than hitting it hard. Generally it is the wear ring, and not a big deal. However it could be more involved as described by some of the others above.

 

[cbogacz]

I'm dealing with what I think is a serious cavitation issue with my 96 sporster. Same deal takes time to hit plane even though engine revs up. If replaced the carbon ring ( kit was 70ish) and also installed a new wear ring and refurbed impeller. All fairly easy to do and shouldn't cost you more than a couple hundred dollars. I just wish all that had solved my problem. Good luck, 2k would be a great deal as that's what I paid for my sporster last month.