97 Challenger Cavatation Question

[enut]

Before spring comes I would like to get a question answered. I noticed that when I had the boat on the water towards the end of the season in choppy water, the boat could barely move. I opened the weedless gate and made sure that no weeds were in there, but it could barely move. The engine was working fine, it made rpm's. The waves could not have been more than a foot or so.

Then after that I went to another lake where the water was very calm and the boat ran fine. I was able to get up to speed about 35-40 easy. Is it normal for these boats to not run well in choppy water? Could this be a sign of a needed carbon seal or wear ring replacement?

 

[bigtexan99]

I used to have a 96 challenger and it had issues getting on plane. It turns out it was the stainless steel ring, and the carbon seal not having enough pressure to 'stick together' and they were slipping. If your driveshaft is original, I would look into a rebuild kit which includes the new C clip, 2 new o-rings, stainless steel piece, and a carbon ring. You can also check your bellows to make sure it is stiff enough.

When your boat is in the water, reach down (engine off) and pull the carbon ring away from the stainless steel piece. How hard is it to do that? Does water come in? Driveshaft rebuild in order.

Tonight, go out to your boat and put the gear selector in F to raise the jet pump cover. Stick a flashlight in there. Then, get on your back under the boat and look into the weedless gate at the impeller...how much light is coming thru between the impeller blades and the wear ring?

To answer your question though, yes, it is normal to have a little extra effort to get on plane in very choppy conditions.. but what you describe as not being able to move points to another problem.

 

[bigJake]

When your boat is in the water, reach down (engine off) and pull the carbon ring away from the stainless steel piece. How hard is it to do that? Does water come in? Driveshaft rebuild in order.

Not sure what you are saying here - if you pull the carbon ring away from the SS ring water will come in regardless of condition. Won't it?

 

[bigtexan99]

Yes indeed, water will come in if you pull away. I wanted him to gauge the effort required to pull the ring away as an indicator that he might have 'slop' in the driveshaft.

 

[bigJake]

That is what I thought you were indicating, just a little ambiguous and I didn't want anyone to misinterpret that water coming in when pulling the carbon ring back in and of itself meant that it needed replaced. I know it should be pretty difficult to pull back, but mine is not very difficult but I have very little cavitation. I don't really know if this is an approved test or not but I usually suggest testing with a little waterproof grease on the carbon ring to see if it creates a better seal and causes it to run better.

 

[enut]

I attached some pics of my pump. I can't get to the boat right now very easily to check the carbon seal since it is in storage. I am sorry for the pics, I am no photographer. Let me know what you guys think.

 

[Seadoobuddy]

How is the clearance between the impeller and wear ring? .040 is the max

 

[howie099]

Some driveshafts have more than 1 grove to tighten up seal. Waterproof grease is the best test, but just for the year of the boat it wouldn't hurt to replace the carbon seal assembly unless you know it has been replaced at one time. Also some styles of aftermarket impellers can help with the boat hooking up in rough water. The wear ring is easy to check with a feeler gauge or by looks if it all gouged up.

Usually with a bad carbon seal assemlby or wornout one you would have the same issue even in calm water. Usually RMP's shoot up and you go nowhere. I would look at the impeller and wear ring first. To replace the carbon ring is 10 times easier than cutting and prying out that stuipd wear ring.

 

[bigtexan99]

Your impeller itself looks good. The clearance between the edge of the impeller and the wear ring also looks good, but the best way to be sure is to measure the gap as noted above.

I would focus on the carbon seal / driveshaft as the source of your cavitation first.

 

[enut]

In the spring I will measure the impeller/wear ring clearance. But I am curious if other people noticed a difference in choppy water verses calm water. Do the boats and skis have a hard time getting going in choppy/rougher water verses calm water? I would like to know if what I have seen is normal?

 

[bigtexan99]

To answer your question though, yes, it is normal to have a little extra effort to get on plane in very choppy conditions.. but what you describe as not being able to move points to another problem.

Perhaps you missed this?

 

[howie099]

It is harder on choppy water to get on the plane faster than calm water. All planing boats or crafts will have more issues planing on rougher water since that is the design of the hull. Implellers and intake grates can help if you are mostly in choppy water.

 

[enut]

Thanks guys for the help, in the spring I will measure the wear ring clearance and check the carbon seal.