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Mac 360 Porpoising

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Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2019 at 4:41am
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Titanium
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Joined: 04 Jul 2014
Location: Manukau Harbour
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I had same motor and boat couldn't get it right at all speeds ended up fitting a power trim and adjusting at different speeds. This hull is sensitive to trim, manual trim adjust till you find sweet spot for speed conditions and load on day. With trim in fast level holeshot but hairy at speed but trim out as speed came up and all good. Powered trim is expensive to retrofit.
Good fishing trip nothing breaks, great trip catch fish.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2019 at 10:50am
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Titanium
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Read thru older posts..
 Check engine is correct height.. WITHOUT the permatrim total waste time doing anything if that is wrong.
 Once correct height.
 Then look at correct prop.. if still porpoising when correctly trimmed at each speed...
 Different speeds require different trim.. faster you go the more trim.
 If still have issues, then look at a 4 blade prop with more rake... blades lean back more. This levers the stern up and bow down.

 Get and know height is right 1st.
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Post Options Post Options   Likes (0) Likes(0)   Quote changnxf Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 2019 at 7:43am
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Thanks Slapper 61
Prior to the electric start Tohatsu 30, I also had a Merc 30 (same short shaft motor) with the Hydrofoil.  Also with tank at front - under front bench seat - had no issues with porpoising at all.  Fixed trim was set to 2nd to last hole.  Admittedly hardly ever on my own in it, always at least someone on front seat.  
Unfortunately I haven't had a chance to resolve the current porpoising problem, but I am definitely going to relocate the motor up a few centimeters.
I will post any results.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 2019 at 5:09pm
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Titanium
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If motor correct height, and porpoising, then reduction in trim is required if the balance loading of the boat is the same.
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Post Options Post Options   Likes (0) Likes(0)   Quote Snappa Geoff Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 2019 at 4:56am
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Just a thought Changnxf, have you taken measurements on the later model 360 with high transom with same outboard on as yours? Replicate height of outboard from where shaft sits at bottom of hull with a mark on shaft then line up mark with the bottom of your hull and that will give you your mounting height. I have later model 360. Used both long shaft merc 30 and have Yammy 30 on now, never had any problems, even beach launching on my own. Beer
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Post Options Post Options   Likes (0) Likes(0)   Quote changnxf Quote  Post ReplyReply Direct Link To This Post Posted: 02 Oct 2019 at 10:20pm
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Thanks Gents
I'll be able to get on to it soon.  All Advice is appreciated.
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Post Options Post Options   Likes (0) Likes(0)   Quote changnxf Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2019 at 11:26pm
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Gents 
Thanks for all the advice.  An update:
I raised the Panther tilt so that it was in line with the top of the transom, lifted by about 60mm, and the anti-cavitation plate is now above the bottom of the hull.  Trimmed right down, lot less bow up on getting up to plane, and with 1 light person and a bucket of sand up front, was able to find a comfortable speed without porpoising.  With two people up front, there was no sign of porpoising at all.  Outboard is now at more acceptable height and not looking like being immersed in the water.  Lot less spray from the motor as well.
Not planning any more adjustments.  Thanks again to all.
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Post Options Post Options   Likes (0) Likes(0)   Quote MacSkipper Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2019 at 6:10am
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Titanium
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Originally posted by changnxf changnxf wrote:

Gents 
Thanks for all the advice.  An update:
I raised the Panther tilt so that it was in line with the top of the transom, lifted by about 60mm, and the anti-cavitation plate is now above the bottom of the hull.  Trimmed right down, lot less bow up on getting up to plane, and with 1 light person and a bucket of sand up front, was able to find a comfortable speed without porpoising.  With two people up front, there was no sign of porpoising at all.  Outboard is now at more acceptable height and not looking like being immersed in the water.  Lot less spray from the motor as well.
Not planning any more adjustments.  Thanks again to all.
Thanks for posting outcome great to hear!
Good fishing trip nothing breaks, great trip catch fish.
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