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Thread: Zodiac / Jet / Cavitation?

  1. #1
    Member MaxBaglimit's Avatar
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    Default Zodiac / Jet / Cavitation?

    Ok guys, help me out here. I have a couple questions. I just bought a used 16 Zodiac with 30 hp Johnson prop. My intention is to get a jet lower unit for it and run up the Sag / Ivishak next year. Not looking to go real far up river, just to 6-10 miles from the road to hunt with rifles for caribou.

    Is this an adequate rig for these rivers?

    I have heard about cavitation issues when using a jet with inflatables. What is the best way to solve the cavitation problem? Any other issues I should be aware of?

    Thanks

  2. #2
    Member Alasken's Avatar
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    IMO, you'll be under-powered with that jet set up. I've run a 16' zodiak with a 55 w/jet and 14' with a 40 w/jet. Both those worked well. From my experience with inflatables and jet outboards is the jet foot has to be a little lower than setting it up on an aluminum boat. It creates more drag, but eliminates cavitation.
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  3. #3
    Member Bullelkklr's Avatar
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    From what I have researched and talked to people on this forum - the best way to avoid cavitation while running a jet on a zodiac is to cut the Vee off of the bottom of the transom, re-work the hypalon, stretching it tight and then re-glueing it. This will eliminate the bubbling created by the Vee.

    Running your zodiac on a shallow river is recipe for zodiac ruin. Imagine that hypalon covered wood transom engaging with multiple river rocks. Now imagine pulling out a smooth grand to have the transom rebuilt.

    I have a 1986 MKIII Grand Raid - so your mileage may vary if you have a newer boat with the speed rails.

    I had AKR&K rebuild my transom on my 15-5" zodiac. They had to do it twice to get it right. It cost me money and patience - lots of both. I now have a professionally built, sturdy, solid, nice looking transom that I don't want to get banged up. No way I would take mine on the sag. I have not been on the sag in the area where you want to go.

    Also - I have taken my zodiac down from Deshka Landing to the Deshka for kings and silvers several times. I have also had her on the little su - up to 10 miles up from the mouth. She doesn't like to go back upstream and even when pumped up hard - basketball thump a watermellon kind of hard - she cavitates several times. That is the nature of the beast in a zodiac. Takes some getting used to, and a feathering of the throttle. This is with a 40hp 2 stroke zuki prop that will run 28mph on the salt in the right conditions with 2 people, dog, and camp gear. Empty, my little zodiac is like a corvette - fun and sporty and quick....okay - I might exaggerate a little sometimes.

    If you are loaded for bou or bear, that 30hp with a Jet on it will probably not make much headway going upstream on the sag or the Su. I would try it on the Su with a light load before you attempt the drive up North. You won't like the upstream performance.

    My uncle has a 18' smoker craft kodiak -- aluminum boat. He is running a 50hp effinrude. With the prop we can go all day long on the ocean at 27mph - sipping fuel. Put the jet foot on it, on the su, and 3 people, a dog, tent, cooler, and a couple Kings - and it takes a long while to get back to Deshka landing in it.

    I have done a lot with my zodiac, not as much as some, but more than others and I just wouldn't take it on the sag or any other shallow river.
    Last edited by Bullelkklr; 10-05-2012 at 09:33. Reason: spelling

  4. #4
    Member MaxBaglimit's Avatar
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    Quote Originally Posted by Bullelkklr View Post
    From what I have researched and talked to people on this forum - the best way to avoid cavitation while running a jet on a zodiac is to cut the Vee off of the bottom of the transom, re-work the hypalon, stretching it tight and then re-glueing it. This will eliminate the bubbling created by the Vee.

    Running your zodiac on a shallow river is recipe for zodiac ruin. Imagine that hypalon covered wood transom engaging with multiple river rocks. Now imagine pulling out a smooth grand to have the transom rebuilt.

    I have a 1986 MKIII Grand Raid - so your mileage may vary if you have a newer boat with the speed rails.

    I had AKR&K rebuild my transom on my 15-5" zodiac. They had to do it twice to get it right. It cost me money and patience - lots of both. I now have a professionally built, sturdy, solid, nice looking transom that I don't want to get banged up. No way I would take mine on the sag. I have not been on the sag in the area where you want to go.

    Also - I have taken my zodiac down from Deshka Landing to the Deshka for kings and silvers several times. I have also had her on the little su - up to 10 miles up from the mouth. She doesn't like to go back upstream and even when pumped up hard - basketball thump a watermellon kind of hard - she cavitates several times. That is the nature of the beast in a zodiac. Takes some getting used to, and a feathering of the throttle. This is with a 40hp 2 stroke zuki prop that will run 28mph on the salt in the right conditions with 2 people, dog, and camp gear. Empty, my little zodiac is like a corvette - fun and sporty and quick....okay - I might exaggerate a little sometimes.

    If you are loaded for bou or bear, that 30hp with a Jet on it will probably not make much headway going upstream on the sag or the Su. I would try it on the Su with a light load before you attempt the drive up North. You won't like the upstream performance.

    My uncle has a 18' smoker craft kodiak -- aluminum boat. He is running a 50hp effinrude. With the prop we can go all day long on the ocean at 27mph - sipping fuel. Put the jet foot on it, on the su, and 3 people, a dog, tent, cooler, and a couple Kings - and it takes a long while to get back to Deshka landing in it.

    I have done a lot with my zodiac, not as much as some, but more than others and I just wouldn't take it on the sag or any other shallow river.
    Wow, thanks for the detailed response. Just the kind of things I needed to know. I guess my Zodiac will be more of a local fishing rig, which is fine.

  5. #5
    Member Bullelkklr's Avatar
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    You really can do a lot with a zodiac. It does almost nothing with lots of comfort, but it is an all utility kind of boat that plain gets the job done.

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