Jazz 120xr Sport Jet Slow out of the hole

darius

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Jul 31, 2010
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4
I recently purchased a '96 Jazz boat that is very slow out of the hole. I would like to be able to pull at least a tube or skiier, but that is currently not possible. Engine seems to run well and coming out of the hole it bumps up to about 4500rpm with the throttle wide open, top cruising speed is about 32mph(gps) at 4600rpm. Seems to take about 10-12 seconds to get on plane with just myself and a small child (230lbs Combined) in the boat. If I have any load at all, a hard turn seems to drop me right off plane also. I've inspected the impeller and wear ring, and the clearance is .010 with no significant damage to the impeller or ring. When in forward gear, the cover over the jet has about 1/4" clearance above the jet. I see other jet boats with much more speed on takeoff and maneuverability on turns. Suggestions on what I might be missing here or how to improve?
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

Sounds about right although top end should be 3-4 mph higher , These are slow out of the hole and take forever to plane , A set of Nauticus smart tabs will help ALOT !! call greg at 800-223-0194 and he will give you the proper part number for your boat . I would check the carb adjustments , are all the throttle butterflies opening at the same time , at WOT are they flat or are they able to go past flat ? If you have a butterfly that is not opening properly you will see the performance loss you are getting .
Also check engine timing .
 

darius

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Re: Jazz 120xr Sport Jet Slow out of the hole

Thanks for the reply kend301!

I talked to Greg at Nauticus and he says that because of the limited mounting space it uses a custom kit that he puts together rather than an off the shelf version. Do you, or other users have pictures of Smart Tabs currently installed on your Jazz or similar boat so I can see how you solved the mounting solution?

I plan on taking a look at the carbs tonight and I'll get back to you with the results.
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

Yes I have pics , here they are , kinda simple , you will use a shorter piston , pre assemble tabs then see how far out you can mount then based on the top mount and still have the proper angle and adjustments .
 

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darius

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Jul 31, 2010
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Re: Jazz 120xr Sport Jet Slow out of the hole

Thanks for the smart tab pics Kend301. Nice to finally see what others are describing.

I was also able to check the carbs tonight, and the upper carb is exactly horizontal at WOT, while the lower carb goes past horizontal by what looks like to be 10-15 degrees. That seems to make some sense now, as I recall when being on the water, if I backed off of WOT by an 1/8th of an inch on the stick I would gain and additional 500 rpms, but by going full WOT it was very sluggish.

Carbs are not really my thing, but I am assuming they should both be aligned identically, and from your earlier post they should not go past horizontal. I see the set screw and linkage that appears to tie the upper to the lower so I'm going to adjust them tonight and if I am way off base give me a shout.
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

You are doing the right thing here , gets the carbs set and you will have a higher top end !
 

Billy 123

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Aug 14, 2010
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Re: Jazz 120xr Sport Jet Slow out of the hole

i have a 96 jazz that was sitting fro six years and never run in those six years i cleaned carbs changed plugs and ahd to free steering cable i put in the water today it ran great didnt miss a beat it planed out at 37mph but slow getting up does the trim tabs make a noticable difference.
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

Yes they help A LOT , call greg at nauticus for the proper application for your boat . 800 223 0194.
 

wilmar

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Aug 19, 2010
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Re: Jazz 120xr Sport Jet Slow out of the hole

Hi, I have a Jazz 120xr and when i am alone it pops out of the hole right away when given WOT and on GPS it runs about 43 mph on calm water. I have smarttabs sx mounted and ajusted them on the lightest resistanthole. When we are on a family trip (2 adults, 4 kids and a big pile of stuff (ski's, vests, suits, food, drinks and more food) is takes about 8 seconds to plane but once in plane it runs like stung by a bee again.. Maybe european water is thinner...
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

Shows what a properly tuned and adjusted boat can do .. 43 mph is perfect for a 120 !
 

wilmar

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Aug 19, 2010
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Re: Jazz 120xr Sport Jet Slow out of the hole

Yep, I am very happy with the Jazz. Just one thing that?s really annoying... waterplants... As long as the waterintake is clean it runs great, but if the water becomes shallow and sucked in waterplants are covering the intake by only like 10 or 20% it immediately becomes astmatic. The engine is revving powerlessly and thrust is gone. Sometimes switching off the engine make the junk go away but most of the time somone has to get in the water and clean the intake by hand (yuk.. one thing the wife doesn?t do).
 

kend301

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Jul 4, 2009
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Re: Jazz 120xr Sport Jet Slow out of the hole

I just throw my 12 yr old daughter overboard and will not let her back on the boat until she cleans the great . It is "tough love" but it works well :D
 

wilmar

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Aug 19, 2010
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Re: Jazz 120xr Sport Jet Slow out of the hole

Ha, d##n right... as previously said, we have 4 kids, so I usually appoint a volunteer.. our 9 yo daughter got lucky and won the jackpot.. a 3 pound dead fish with no head..:eek::eek: covered in a sort of rotten seagrass and a plastic bag.. Should have caught that on camera... She planed out of the hole even faster than the Jazz...;):D
 

kend301

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Jul 4, 2009
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1,005
Re: Jazz 120xr Sport Jet Slow out of the hole

Glad to see someone else using my fix with good results :D:D
 
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