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Thread: Permatrims

  1. #1
    Full of shit Ryan_Songhurst's Avatar
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    Permatrims

    Thinking of putting a permatrim on my outboard. It's a 25hp Mariner and pushes a 3.8m Zodiac inflatable. Outboard goes really well on this size boat, problem being that it's very happy in the front and keeping it down with only a couple of people and gear on board is a bit of an art , when on the plane it's fine and nice and stable and goes like a rocketship it's just that coming on and off the plane it likes to put the front up. Am I right in thinking that a permatrim would go a long way towards correcting this behaviour and possibly even allow planing at a much lower speed?
    270 is a harmonic divisor number[1]
    270 is the fourth number that is divisible by its average integer divisor[2]
    270 is a practical number, by the second definition
    The sum of the coprime counts for the first 29 integers is 270
    270 is a sparsely totient number, the largest integer with 72 as its totient
    Given 6 elements, there are 270 square permutations[3]
    10! has 270 divisors
    270 is the smallest positive integer that has divisors ending by digits 1, 2, , 9.

  2. #2
    Almost literate. veitnamcam's Avatar
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    Yes.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

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    Yes it will. You may find once fitted that you need to ring the leg a notch lower.
    Summer grass
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  4. #4
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    I've had one on a couple of boats I've owned, although not rubber boats but yes it let's you plane at lower speeds and can help you keep the nose down.

    Sent from my CPH1903 using Tapatalk

  5. #5
    Almost literate. veitnamcam's Avatar
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    Quote Originally Posted by Woody View Post
    Yes it will. You may find once fitted that you need to ring the leg a notch lower.
    I have found the opposite, with the plate above the prop preventing ventilation I went up a hole improving speed and economy.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

  6. #6
    MB
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    My mate had one put on his Fyran. It went from an appalling ride to just a bad ride, so yes, I think it will do what you want.

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    Quote Originally Posted by veitnamcam View Post
    I have found the opposite, with the plate above the prop preventing ventilation I went up a hole improving speed and economy.
    Same deal here. Raised the engine until there was barely a few mm running across the top of the permatrim when planing.
    No issues with cavitation. Same configuration for the last 10 years, and still happy with it.

  8. #8
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    Quote Originally Posted by Woody View Post
    Yes it will. You may find once fitted that you need to ring the leg a notch lower.
    I am referring to trim angle, not depth of cavitation plate.
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    Then you find another school of thought. Some will say that these devices cover up inherent flaws in the boat design or use.

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    MB
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    Quote Originally Posted by outlander View Post
    Then you find another school of thought. Some will say that these devices cover up inherent flaws in the boat design or use.
    That's my understanding too, but if you've fiddled with everything else and can't get it right, then go for a permatrim.
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  11. #11
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    i look at it as extending the planing speed as speedboats are designed to work at certain speed range but when conditions dictate travelling slower thus the permatrim helps extend the lower end of this otherwise get a flatter hull and sacrifice higher speed.

  12. #12
    Almost literate. veitnamcam's Avatar
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    Quote Originally Posted by outlander View Post
    Then you find another school of thought. Some will say that these devices cover up inherent flaws in the boat design or use.
    People who say that usually give advice like get a bigger boat.
    I think virtually all small boats would benifit from having one fitted.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

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    Yes a permatrim will help keep the nose down
    but on lightly loaded small boats eg driver only they can lift too much of the boat out of the water making them a bit squirrelly

    your other option is going for a prop with more lift ie a 4 blade but propping isnt an exact science either
    what prop is it running at the moment?


    permatrims can also apply excessive pressure to the leg of the outboard think big lever with most of the weight of the boat on it


    have just re propped and removed se300 hydrofoil on current 4.5m boat and have gained 6kph and planing ability hasnt changed
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  14. #14
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    Works well on my 18hp tohatsu pushing 12ft parkercraft

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    I have an alloy one on a 30 on a 4m alloy pontoon boat. I had heard that in a following sea on a surf break they can shunt you around a bit in a small boat but I have not experienced this myself. The sturdy alloy ones like mine are are handy for getting in and out of the boat as you can stand on them if you are not too hefty. I think they are also supposed shave a bit of top speed off?

 

 

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