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Thread: Permatrims

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    Default Permatrims

    Anybody have experience with permatrims? Just got a 25 foot tomcat and have heard a lot of other cat owners using them. Just wondering if they really do make a difference.

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    Member spoiled one's Avatar
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    Quote Originally Posted by griff View Post
    Anybody have experience with permatrims? Just got a 25 foot tomcat and have heard a lot of other cat owners using them. Just wondering if they really do make a difference.
    No personal experience here, Griff, but this may help you out. I am considering trying a pair on my GC. Anything to gain some MPG!

    http://www.thehulltruth.com/forums/f...iew.asp?fid=12
    Spending my kids' inheritance with them, one adventure at a time.

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    Member DMan's Avatar
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    Quote Originally Posted by spoiled one View Post
    No personal experience here, Griff, but this may help you out. I am considering trying a pair on my GC. Anything to gain some MPG!

    http://www.thehulltruth.com/forums/f...iew.asp?fid=12
    I would think these would help with twins as well to keep from cavatation in hard turns. Then motor hight wouldn't matter as much.
    ... aboard the 'Memory Maker' Making Memories one Wave at a Time!

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    Member spoiled one's Avatar
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    Quote Originally Posted by DMan View Post
    I would think these would help with twins as well to keep from cavatation in hard turns. Then motor hight wouldn't matter as much.
    From what I can gather, if you are using permatrims, you can run your motors up at least one hole and sometimes two. Less motor in the water = better MPG...right?
    Spending my kids' inheritance with them, one adventure at a time.

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    Member DMan's Avatar
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    Quote Originally Posted by spoiled one View Post
    From what I can gather, if you are using permatrims, you can run your motors up at least one hole and sometimes two. Less motor in the water = better MPG...right?
    S.O. Makes since to me! Maybe if it works for you I will just have mine installed at normal height and install these to begin with.

    Griff, sorry for the hijack, I haven't seen many OB with these but I seem to recall allot of out drives with them. Might be worth talking to some people at the launches.
    ... aboard the 'Memory Maker' Making Memories one Wave at a Time!

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    Member Rod in Wasilla's Avatar
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    Thumbs up Sure worked for me

    Ok, so it's not exactly apples and apples, but I installed a Permatrim on the 90hp Johnson 2-stroke hanging off my 17-foot Arima Sea Ranger. It's a short, wide, stern-heavy boat that weighs in at about 3400# fully loaded for a typical weekend trip (scaled two weeks ago, including the trailer). I have a Navman fuel flow meter tied into the GPS and noticed a fairly significant increase in MPG at our typical 24-27 MPH cruise after the Permatrim install (from 3.2 to 3.6 = 12.5% increase) without moving the motor up any. The boat also rides smoother in all conditions without porpoising, and the available low speed cruise has dropped 3-4 MPH (can go slower without falling off plane). On the top end, I lost 1-2 MPH, but I never run on the top end anyway except for an occasional short burst.

    Hope that helps.
    -Rod

    *Note: For the sake of full disclosure, I should mention that my unit is not Permatrim brand. I fabbed one up in my shop using Permatrim dimensions.
    Quote Originally Posted by northwestalska
    ... you canít tell stories about the adventures you wished you had done!

  7. #7

    Smile My experience

    Quote Originally Posted by Rod in Wasilla View Post
    Ok, so it's not exactly apples and apples, but I installed a Permatrim on the 90hp Johnson 2-stroke hanging off my 17-foot Arima Sea Ranger. It's a short, wide, stern-heavy boat that weighs in at about 3400# fully loaded for a typical weekend trip (scaled two weeks ago, including the trailer). I have a Navman fuel flow meter tied into the GPS and noticed a fairly significant increase in MPG at our typical 24-27 MPH cruise after the Permatrim install (from 3.2 to 3.6 = 12.5% increase) without moving the motor up any. The boat also rides smoother in all conditions without porpoising, and the available low speed cruise has dropped 3-4 MPH (can go slower without falling off plane). On the top end, I lost 1-2 MPH, but I never run on the top end anyway except for an occasional short burst.

    Hope that helps.
    -Rod

    *Note: For the sake of full disclosure, I should mention that my unit is not Permatrim brand. I fabbed one up in my shop using Permatrim dimensions.

    Rod and Griff,

    I have had a similar experience with my C-Dory 22. I love them dearly and putting them on for better fuel economy may sound good in theory, but in practice the opposite of what you think should happen, happens - meaning more fuel is used, not less. This is especially true on a fuel flow meter in given situations at a given speed. Griff, you should really be asking this question on the C-Brat Site. You will likely get an answer from someone with a boat just like yours.

    For those of you that are wondering why, the biggest culprit is the fact that when you trim the bow of the boat down with outboards without permatrims, there is only so much bite available to force the bow down. With permatrims, there is significantly more bite available, proportionally more leverage, and they push the bow down very, very aggressively. In my boat, because it is a flat bottom boat, this really helps the boat's ride in steep, heavy chop. I can go faster, it doesn't pound nearly as much, and the boat is seemingly more stable unless in a crossing sea. In this situation, the boat burns more fuel than it did before, however, the boat is traveling faster than it could even dream of comfortably going before. It is a trade off.

    In normal situations, without steep heavy chop, the trim of the boat is not nearly as aggressive, and I can honestly say that I have no noticeable difference in fuel economy at all with permatrims installed. Top speed does not seems to be effected much, if at all either. But, if you trim the bow of the boat full down, fuel economy certainly is impacted and it is a substantial amount.

    In my humble opinion, the slight bit of extra fuel that is sometimes used when using permatrims when considering all the very large positives: better ride, better hole shots, more stable boat, and better boat performance when fully loaded (the boat, not you ) is well spent.

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