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renegade1
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Discussion Starter · #1 ·
:) Hello, I am new to this board, and Jet boats. It looks to me, that it is full of helpful advise. Like any other boater, I am looking into upgrades for speed. I have a 2002 21ft Renegade with a 385 hp marine power. I have been looking into what it would take to increase HP and improve my jet performance. I have been told aluminum heads and a cam will increase hp, and a nozzel extension and impeller will help with the jet performance. Has anyone had success with those upgrades? The big question is, will I have to sell a kidney to pay for them? Thanks
 

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"Try it Now!"
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:) Hello, I am new to this board, and Jet boats. It looks to me, that it is full of helpful advise. Like any other boater, I am looking into upgrades for speed. I have a 2002 21ft Renegade with a 385 hp marine power. I have been looking into what it would take to increase HP and improve my jet performance. I have been told aluminum heads and a cam will increase hp, and a nozzel extension and impeller will help with the jet performance. Has anyone had success with those upgrades? The big question is, will I have to sell a kidney to pay for them? Thanks
Nice boat! leave it stock and have fun with it is my advice ;) :)hand
 

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How much of a performance increase are you looking for and where? (low down acceleration or top speed?)
Just the heads being aluminum wont increase performance, the idea is getting some high perf heads that flow better...but that depends upon what you have already...
What speeds and rpm are you attaining now? These can help pinpoint any issues, such as a worn out pump...

So far, it looks like you have a pretty nice boat :D
 

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The more you trick it out the more tinkering you will do with it at the lake/river.

Just a heads up HP costs money, how fast can you afford to go? Those boats do pretty good in stock configuration, would take a lot of power and a lot of money to get a marginal gain considering what the hull was intended for.

~Brian
 

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renegade1
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18 Posts
Discussion Starter · #5 ·
It runs 55-60 depending on load now. Not bad,but I was hoping to get it to run around 70. I only want to spend 2-3 thousand on it right now. I was just wondering if there was some decent upgrades to consider. I do not even know where to start. I am happy with it now, but I am bad at leaving well enough alone.
 

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1 of 3 Stoojz
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Renegade, I have done everything to which you have referred (your quote "I have been told aluminum heads and a cam will increase hp, and a nozzel extension and impeller will help with the jet performance"), at least twice, in the 18 years that I have owned my barge. If you are looking to benchmark against a similar hull, see my previous thread below regarding my 20.5' 1988 Caribbean hull, with pictures.

http://www.performanceboats.com//showthread.php?t=34938&highlight=caribbean20

Happy to share more details, but if there is one general rule in my experience, airing out the hull is the only time I have spent money on a performance upgrade that actually exceeded expectations. In my case, it was a ride plate, shoe and droop. I already had the Place Diverter, and that should be the first place you should start, if not already done so.

I estimate the ride plate, shoe and droop probably gave me a 3 - 5 mph increase on the top end. The hull airs out a bunch more, and its like shifting to overdrive when you trim it out. I did get a bit of porpoise in the ride, but you can trim your way through it.

In closing, if you are paying the normal shop rate of about $90/hr, which is what I paid, you WILL have to sell a kidney for any of this stuff. I never came away for less than $4 yards when paying for a shop to do it, and unfortunately, I always paid a shop to do it. More money than time.
 

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renegade1
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Discussion Starter · #9 ·
Thanks for the info so far guys. I do have a place diverter already, but the droop and ride plate sound interesting. I could probably do that myself if I can find the parts. Is the droop different than a nozzel extention? Sorry, like I said, I am new to the jets.
 

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Thanks for the info so far guys. I do have a place diverter already, but the droop and ride plate sound interesting. I could probably do that myself if I can find the parts. Is the droop different than a nozzel extention? Sorry, like I said, I am new to the jets.

You will have to have your intake machined for a shoe and rideplate in some (most) cases.

10 to15 MPH is big money on any jet boat IMHO leave it be, and find yourself 5000.00 performance boat to play with and enjoy your family boat. As stated above you will all way be fussing with it and you can drop 5000.00 easy trying to get 70 mph out of it. good luck:)devil:)devil:)devil
 

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renegade1
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Discussion Starter · #11 ·
Another boat huh. I like the way you think. With all of this new information, I am starting to lean toward leaving it alone myself.
 

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2nd boat

Another boat huh. I like the way you think. With all of this new information, I am starting to lean toward leaving it alone myself.


IMO you would be money ahead and much happier. 70 mph in 18 ft low profile boat is fairly easy and if it set up right it can very reliable and fairly safe. 70 in your boat will be very hard on it as far as pushing it.:)devil:)devil:)devil
 

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Sit N' Spin
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1,423 Posts
I would say before you worry about trick hardware, focus on the powerplant and drive first. You want that running efficiently before you get into all the hull tuning hardware.

The first thing you may wanna do is place a straightedge on the bottom from the transom to about a foot or two in front of it. If you see a gap between the straightedge and the bottom, this means the bottom has a "hook" in it. Depending on how much hook the bottom has, boats running at high speed wih a hook will tend to bury the nose of the boat no matter what you do and you'll end up having a hard time trying to lift the boat off the water at speed. The boat would ride much more efficiently with less hardware headaches without the hook in the bottom if there is one, so if it were my boat I'd gut it and send it to a good shop that knows boat bottoms to have the hook taken out of it.

You can use hardware to correct for it, but IMHO this would be merely a band-aid for a problem that can be corrected by the above mentioned procedure.

Also, if you have a bow mounted fuel tank, I would advise ditching it and going with side tanks in the rear. This will redistribute the fuel weight fro the front to the back and also make it easier to get the boat to "air out".

Have the pump (pump is slang for jet drive, since it is merely a high pressure water pump) rebuilt with tighter clearances. This will make the pump more efficient (move more water with less RPM due to minimizing pressure losses within the pump). However this will also pose a greater load on the engine so on the flipside of that, you'll wanna increase horsepower to be able to turn the extra load to a decent RPM (around 5000 RPM).

If you plan on running 70, I highly advise you replace the rock grate with a loader grate. My pump guy is Jim Coffee at Performance Jet, and according to him pumps traveling through water over 55mph cannot load properly without one and you will experience high speed cavitation at that speed. He makes and sells the White Lightning loaders which is what I'm currently running. My 18' is pulling an A cut impeller to 5200RPM and the boat is topping out at 77mph with 450-500hp.

Hope this helps.
 
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