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  1. #1

    Riva RPM Kit Failures

    I installed the full Riva RPM kit minus impeller and sponsons, air filter, rideplate, primary waterbox mod, removed secondary muffler. On a75degree day I could only pull 62 on the speedo, the same as before the kit. Three bars past 7,000 on the rpms. On hot days, I sometimes only get one bar or no bars past 7,000 rpms. Running with 1/3rd tank of fuel, however it was last years fuel. I have GPS'd my ski last year and found that the speedo is 1-2 mph faster than the GPS speed, so I am maybe topping out at 60mph. This is what a stock ski should pull. I am stumped and I hope to hell I haven't wasted almost $1000. Ski has only 56 hours on it.


  2. #2
    madtown_chris's Avatar
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    you need to have gps speeds for any help to be beneficial....60-62 stock is accurate

    I'll say if you want this kit to be the most beneficial, you have to be patient and do your homework...

    *chk oil level, a lot of machines are over-filled
    *is rideplate flush, smooth with intake grate, no excess silicone
    *if rideplate is all good you probably want to fill the holes

    stick around there's lots of people that will help and get you into the mid 60's

  3. #3
    Just a H-20 HO....Need I say More! Mykull's Avatar
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    Quote Originally Posted by madtown_chris View Post
    you need to have gps speeds for any help to be beneficial....60-62 stock is accurate

    I'll say if you want this kit to be the most beneficial, you have to be patient and do your homework...

    *chk oil level, a lot of machines are over-filled
    *is rideplate flush, smooth with intake grate, no excess silicone
    *if rideplate is all good you probably want to fill the holes

    stick around there's lots of people that will help and get you into the mid 60's
    60-62 stock?? That isnt normal...if thats what your runnin i can stomp the hell outta your ski with my honda. Both of you need to start checkin over your skiis to findout whats leakin/loose or oil soaked. I ran 68.4(gps) ,5 minutes after i did my 5hr breakin...stock.

    Toby, Im runnin easy 71s without the RPM kit, Have you checked your oil level? Or your intercooler? Plugs? One of the things the Ultra loves is fresh air, so get some air into the hull. Do a forum search, we addressed alot of this stuff along time ago.

  4. #4
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    I think he has a 15f, stock is @61 mph...........

    You need to istall the impellar to get the most benefit from that kit, did you install the intake grate also?, if you did that will also slow you down........put the imlellar in and you should see an increase in speed.....

    I did the Rideplate, home made air intake and Rivas free flow exhaust , I ran a 65.3 on GPS, but it seemed to bounce more than my liking in chop or when riding 2 up, so I shimmed the back of the ride plate down a little to smooth it out, now I run a consistent 64.5 mph GPS........with very little or no bounce.......

  5. #5
    inchadeboca's Avatar
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    there are alot of things to check as all of these guys are correct as far as what has been mentioned. oil level is imperative. if your motor is drowning in oil, then there will be a perf loss indeed. go over EVERYTHING check for exhaust leaks at the coupler areas of the free flow where it meets the exhaust outlet and on top at the h2o box. a slight leak will cause a loss inperformance.... also, not specific to the 15F, but some aftermarket rideplate angles lead to speedos to misread and thats not much to say as far as speedo readings, b/c they are never accurate to begin with. DO not go by speedo readings, just b/c your speedo said 60-62 before and now it only reads 60, doesnt mean u lost performance = Borrow a GPS from someone or buy a one !!!. now if you feel a seat of your pants performance loss, which most of us who know our boats well can tell, its a different story.
    most importantly did you seal up the rideplate, shoe, grate area well with silicone. did u use cheap silicone? use some 3M 5200 if not = bad cavitation.

    also did u opt for the rd grate or stocker ??

    holy geezus , i just read u did not put in the prop. your motor is breathing alot easier now, i really dont think the stock prop is gonna do well with that. u need a solas concord. i can bet my bolas that the prop has something to do with this

  6. #6
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    5200? I guess you dont plan on taking your ride plate off ever do you? lol

  7. #7
    inchadeboca's Avatar
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    it dries harder than silicone i agree but sticks much better, but i have always used that stuff on all my skis and yes its a bit of a pita to take off, but it can be done.
    gee i wonder why riva recommends it ?
    Last edited by inchadeboca; 06-05-2008 at 02:06 PM.

  8. #8
    madtown_chris's Avatar
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    Quote Originally Posted by Mykull View Post
    60-62 stock?? That isnt normal...if thats what your runnin i can stomp the hell outta your ski with my honda. Both of you need to start checkin over your skiis to findout whats leakin/loose or oil soaked. I ran 68.4(gps) ,5 minutes after i did my 5hr breakin...stock.

    Toby, Im runnin easy 71s without the RPM kit, Have you checked your oil level? Or your intercooler? Plugs? One of the things the Ultra loves is fresh air, so get some air into the hull. Do a forum search, we addressed alot of this stuff along time ago.

  9. #9
    Having Fun jp1300r's Avatar
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    Usually just changing ride plate will get you past 63 even with a full gas tank. If you still have stock prop and did everthing else, you should be at 5-6 bars over 7K. And spinning prop out of the hole. You have some kind of installer problem is my guess. Is your plate hanging down in the front? Sometimes you have to massage it a little to fit good. Leave those two rubber pieces out and use silicone marine RTV. The plate should be flush at the front. Did you do waterline mod? Did you do waterbox internal mod? I think you did just checking. Check coupler at exhaust manifold and waterbox. Burn thru, leaking. Stock speedo is 2-3mph high up to 70mph.

    Toby you didn't waste your money. You just need to figure out were you went wrong with the install.

    I reread your 1st post again. If the install looks good to you, you need to look at your fuel, fuel pump, fuel filter, injectors. Your ski is not running right and you could damage it by continuing to run it. Stock ski should pull 3 bars in the 100degree heat. Also, check and see if you are getting full throttle at the TB. Oil level of course, too.

    Good Luck, JP

  10. #10
    madtown_chris's Avatar
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    Harry, JP, It doesn't seem like his rpms are high enough to warrant the prop change yet, looks to have different issues...

    Toby any feedback?

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