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  1. #1

    WARNING to all people running a RAD4 driveshaft seal. Please read.

    My disclaimer:

    PLEASE NOTE: I am posting this ONLY to share my experience with the other members of Greenhulk. It is not my intention to flame the manufacturer of the RAD4 driveshaft seal, anyone who works for or sells RAD4 driveshaft seals, or anyone who likes and/or endorses them.

    I recently had a leaky carbon ring and decided to go with a RAD4 driveshaft seal to replace it. I thought that the RAD4 would be a good replacement because it fixed that issue along with eliminating cavitation.

    THREE HOURS after installing and greasing the RAD4, it failed. I was launching in the Connecticut River and when I tried to start my ski it was locked up. I tried again to start it and the ski started up and then reved up, but went nowhere and there was a terrible vibration throughout the hull.
    I immediately brought it back to the ramp and put it back on the trailer and water started gushing out of the bottom of the ski. Immediately, I knew what had happened. I lifted the seat and once the water drained out, I could see that the RAD4 was blown to pieces.

    On the drive home, I began to think about what had gone wrong and figured that the bearing inside must have seized which is why the driveshaft was locked up. When it did spin, it spun the boot and tore it to pieces leaving a 2" gaping hole in the bottom of my ski. I was DAMN lucky to be right at the ramp when this happened, needless to say.

    After the blowout, Beerdart and I decided to take it apart and inspect the seal to see the damage and evaluate the seal itself. Upon further inspection, we were shocked to find that the quality of the RAD4's materials is highly questionable and that there are some legitimate safety concerns as a result.

    This is what we found out:

    1) NOTHING inside of the RAD4 is made of stainless steel. NOTHING.
    This includes the bearing itself as well as the seal-spring. The spring sits directly in the water so I have absolutely no idea why this part isnt stainless steel. I do not know how long this part is expected to last. This type of seal has been around for years and it always uses brass or stainless bushings or bearings inside.

    2) The coupling is made of silicone and is thin. The RAD4 uses petroleum grease whcih will eat away at the coupling and ruin it or soften it causing it to pop off. It should have a beefy rubber boot instead.

    3) The coupling is not rated for vacuum.

    4) There really should be some sort of bracket to hold this thing in place in addition to just the ring clamps because there is a heavy load on this coupling under acceleration. Unfortunatley, there is nothing around it to mount a bracket to.

    5) The ring clamps provided are also not stainless steel.

    In conclusion, it is really disappointing that a part that is not only expensive, but also intended to be used in ocean riding and on such high performance machines uses such cheap materials. I do not see one of these lasting for any length of time due to any or all of the aforementioned items. The biggest issue being item #1 above. It would not have cost the manufacturer THAT much more to use stainless steel materials.

    My assessment of the product is that while it may be a 'race proven' product, it is not a good product for the recreational rider. It appears that it needs to be greased and monitored constantly and is still questionable at best due to the inferior parts that it is composed of.
    If the RAD4 had a brass bushing inside it, it could go 50hrs before re-greasing. Instead, mine lasted three and blew out before greasing it a second time. In the end, Im sure that I am at fault for not greasing it after the first ride although [arguably] it should not have mattered after only three hours.

    I am very disappointed and would not recommend this product to anyone.

    The carbon ring may not hold up as well as wed like it to on a ski with a bigger supercharger and etc BUT if a carbon ring fails, it will likely just leak, not blow out completely and sink your boat. A bilge pump can save you from a carbon ring failure but if a RAD4 fails and you arent near shore, you are in BIG trouble.

    I hope this information is helpful.

    Again, I am posting this only to share my experience and to show what we found when we inspected the RAD4 after the blowout. I encourage people to post up and share their experiences, however, please avoid making superficial judgments and/or harsh judgments without having any experience with or knowledge of the product.
    Last edited by caliburst; 10-26-2009 at 06:34 PM.

  2. #2
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    James brought his Ski over tonight so we could pull the pump and the failed Rad 4 out. I must say that the materials used in this thing is all wrong.

    1) Silicone hose the is not vacuum rated
    2) Silicone hose that is not compatible with petroleum grease.
    3) Seal garter springs made from carbon steel.
    4) Needle bearing made from carbon steel.

    Our plan is to replace the hose with one that is vacuum rated and petroleum compatible.

    Replace the seals with ones that have a SS garter.

    Replace the needle bearing with a brass bushing or a SS bearing.

    This bearing and seal only have 3 hours of run time.

    Here are some pics of the removed parts.

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  3. #3
    Nonstop, all day, everyday. 01xdime's Avatar
    Join Date
    Aug 2005
    Pasadena, MD
    Hey Twelves bro i'm not saying the RAD4 seal is good or bad or anything and i run a carbon seal myself BUT. Carbon seals can completely disapear! I know someone who broke a motor mount and his carbon seal broke and was sucked right trough the pump and he went down like a rock. Bottom line is no matter what we put in there no matter how good it is if it the engine isn't lined up good, the driveshaft isn't straight, or if it isn't taken care of it will sink you. I'm not saying this was your case. Now as far as the materials the seal was made from i'm kind of shocked myself.

  4. #4
    Well of course, nothing is fail-proof but I like my chances with a carbon ring a LOT better than with the RAD4. 9/10 times, a carbon ring leaks and doesnt blow out completely.

  5. #5
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas
    Good information to post. so, is RAD going to make it right?
    also, this is a good documentation where RAD can use this information to improve upon their product as this has been put to real life use....right?....products are tested and feedback is given to the manufacturer on how it performs.

    How long has this seal been out?
    How many others have had this happen?
    Is there an alternative seal that does the same w/o any machining of the driveshaft?

    How are the other seals of this similar setup designed?

  6. #6
    No Billie. Unfortunately, Ive taken a huge loss on this deal.

    I was initially promised a refund by SkiMD but he later retracted the refund offer because he was upset over my posting this thread and I got nothing. I lost somewhere in the ballpark of $500 when all was said and done
    Last edited by caliburst; 11-06-2009 at 02:10 PM.

  7. #7

    Join Date
    Mar 2007
    Perth, Western Australia
    Ive had my RAD-4 seal in for 30hrs.. The shaft has to be machined to 28mm, not 28.05 or 27.09mm if the maching isnt bang on it will cause problems.. If you walk into a machine shop and ask for your shaft to be machined, and tell em what its for SOME machinists MIGHT think phuck it its only a jestski do the job in one cut and thats that.. You should then check it yourself with a MICROMETER not a cheap digital vernier caliper. Check the shaft on four points and that its bang on 28mm, you wont be able to do it properly with a cheap vernier caliper.. DONT take the shops word for it, check it yourself.. I dont like reading about these failures or supercharger failures, but its good to compare information and prevent more failures..I WILL KEEP GREASING MINE AND HOPE FOR THE BEST, at 50hrs i will rebiuld it, also have a 1100gph bilge installed I HOPE I NEVER HAVE TO USE IT..

  8. #8
    RXP 260 X Short Course Veteran RXP244's Avatar
    Join Date
    May 2007
    Auckland, New Zealand, New Zealand
    OK. Understand. But I also have been running one of these seals for many hours. I will admit that perhaps I didn't grease mine quite as frequently as I should have. But I put 35hrs on my first bearing before i renewed it. And only because I could. I was putting a new driveshaft in. I could have done many more hours on it and it looked like the day i put it in. And another thing is I have never had any thing that even looked like rust in my bearing.

    I am struggling to understand how you had such a spectacular failure.

  9. #9
    ok, I have never installed the RAD4 driveshaft seal kit in any of our customers ski's, because the factory carbon ring holds up just fine, if it is checked after hard riding!! But I will tell you Sea Doo used this style of coupler assembly from 1988-1995 on every ski they made! I have to replace tons of them a year because of not being greased, seal failure, or just worn out. The Carbon ring setup is much more user friendly and maintence free. The old seal carrier needs constant maintance, and must be greased often!! but even if you do, it will still fail sometimes!! the outer seal sits in water all the time and has constant pressure on it!! I will also say that we have installed many aftermarket seal kits over the years and they never hold up!! they will usually last about 20-40 hours of riding before they fail, The aftermarket ones that we installed were not made of stainless steel and the outer seal would fail. I know if the old seal carrier set up was better Sea Doo would still be using it!! not the carbon ring

  10. #10
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
    Join Date
    Aug 2007
    Tampa Bay, FL
    Quote Originally Posted by WMFwatercraft View Post
    I know if the old seal carrier set up was better Sea Doo would still be using it!! not the carbon ring
    +1... The carbon seal design has been around since 96 and for a good reason! Less maintenance and less cause for failure. If you have good motor alignment, check for broken motor mounts every now and then, and replace the accordion boot every 100 hours... you can pretty much not worry about it causing any issues!

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