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Old 07 September 2010, 08:57   #11
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Country: Australia
Town: Cairns
Boat name: KAHUNAS
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Engine: 30 Tohatsu
MMSI: wft is a dsc mmsi ?
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I would further inpsect your motor for damage, as i know for sure that a 40 hp on a Zapcat, will plane with no issues, whether it be 1, or 2 up, and pretty much regardless of sea conditions. The fact that you cannot plane with a 40 hp and factory prop, would imply that the issue lies elsewhere. I can't see how a change in prop will cure this.
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Old 07 September 2010, 14:34   #12
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Country: UK - Wales
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Boat name: zapcat 74
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Engine: tohatsu 50
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Yes, i agree. Sounds like a problem elsewhere. I've used an aluminium prop on a zapcat, and it doesn't cause the problems you are describing.
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Old 08 September 2010, 00:25   #13
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Country: Canada
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I would only consider a stainless steel prop if I were boating in an area that I was certain was clear of reefs & submerged rocks. While an alloy prop is not as efficient as SS, it can be a (relatively) inexpensive sacrificial component that might save the more pricey components (gears) if a rock is struck by the proper. Always carry at least one spare prop with you.
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Old 26 September 2010, 16:34   #14
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Country: UK - England
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Make: Avon SR4
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replaced prop with 14p powertech - boat now handles like a missile, no problems with cavitation. engine fully inspected - no problems elsewhere. must have been a purely prop based problem after all and is now sorted - Im one very happy man!

only drama of the day was when the engine wouldnt start - checked everything, still couldnt see the problem. finally friends girlfriend noted my kill cord was attached to me somehow at both ends. durr! i suppose it doesnt really get safer than that - i wasnt going anywhere!

thanks for the advice chaps and chapettes!
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Old 27 September 2010, 15:12   #15
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Country: UK - Wales
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Boat name: zapcat 74
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glad you got it sorted. Really surprised that the tohatsu prop caused you so much
grief. As I said, used one on my old boat and it was fine. Strange
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Old 27 September 2010, 15:45   #16
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Quote:
Originally Posted by deeyup View Post
glad you got it sorted. Really surprised that the tohatsu prop caused you so much
grief. As I said, used one on my old boat and it was fine. Strange
Wasn't it a Yam prop originally fitted?
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Old 29 September 2010, 12:00   #17
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Quote:
Originally Posted by rik_elliott View Post
replaced prop with 14p powertech - boat now handles like a missile, no problems with cavitation. engine fully inspected - no problems elsewhere. must have been a purely prop based problem after all and is now sorted - Im one very happy man!

only drama of the day was when the engine wouldnt start - checked everything, still couldnt see the problem. finally friends girlfriend noted my kill cord was attached to me somehow at both ends. durr! i suppose it doesnt really get safer than that - i wasnt going anywhere!

thanks for the advice chaps and chapettes!
Great news Rik! I'm not sure why so many others are baffled that this was a prop issue. Occam's razor at work here - the first thing to suspect based on what you described in the original post, would be a spun prop hub, which is what it turned out to be. It doesn't matter all what the material or pitch of the prop is if the hub is spun, you will only get thrust from the prop while at minimal throttle.
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Old 30 September 2010, 02:58   #18
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Country: Australia
Town: Cairns
Boat name: KAHUNAS
Make: Zodiac
Length: under 3m
Engine: 30 Tohatsu
MMSI: wft is a dsc mmsi ?
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Posts: 82
Quote:
Originally Posted by prairie tuber View Post
Great news Rik! I'm not sure why so many others are baffled that this was a prop issue. Occam's razor at work here
Still baffled myself, because as Deeyup and myself mentioned, have run around in 4.1's with 40's, 50's, both standard and aftermarket props, and never experienced any of the issue's that the OP did.

If the hub was sorted in the original prop i'd put money on it there would be no planing issues

Anyways glad you have it sorted, and that you are finally enjoying yourself.
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Old 01 October 2010, 09:25   #19
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Country: UK - England
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Make: Avon SR4
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as point of comparison:

Original prop - bubbles, high revs start on coming up to planing angle. very rarely got on the plane and when it did went well.
New bunny prop (with new hub) - as above.
New semi cleaver (with new hub) - planes an absolute treat - muuuuuch faster than my old avon (no gps speed yet). gets up on the plane without any real slip reliably every time.

I wonder if its because I have a cat sib made locally rather than one of the more established (read: better) brands - my prop does sit about level with the centre of the highjackers with the engine as low as it can go which i understand is a level most people have to raise their engines to hit? maybe the transom is a bit poorly designed or the tubes oversized? I guess it was just running too shallow as soon as it tried to get up on the plane, so a surface breaking prop tolerated that better?

not that it really matters - it works now and i couldnt be happier!

I meant to say prairie tuber - that boat of yours looks excellent. I read (somewhere) you had it custom built with hypalon - how much did it set you back?
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Old 04 October 2010, 10:45   #20
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Country: UK - Wales
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Boat name: zapcat 74
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Posts: 16
That could the answer??

I thought you were running a Gemini zapcat. So maybe your generic cat has the top of the transom too high. You can't get your motor low enough?

As you say, the semi cleaver being surface piercing is made to work the way you are set up.

Glad you are on the move now
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