Old j30mk2 porpoising

[wairoacoastie]

I?d better put some pic up , but anyway I?d picked up a neglected old j30 mk2  , rubbed it back resprayed everything , gave the whole thing a big birthday , and it?s looking mint . Chucked it in the local for a test run and it porpoises like a epileptic dolphin .  It?s still got the old gates on it , and yea I know they a dog , but woul be nice to keep it original as , I did put some bog on the top of the gates to try trim it down , no joy. ( but the gates aren?t very ?trim friendly?.  Should I just chuck a noz  on it n wedge it , is a ride plate under the unit a better idea or just a compromise ?   I?m just gonna sell the whole thing on but I won?t sell off  unless it all goes mint. 
A clue is someone a long time ago has put a few extra layers of glass on the bottom. Not block perfect flat but reasonable to the eye and looks good. Everything is factory bog standard with Essex v6 and 2 stage of. Original layout.
Suggestions ?  Forget the gates n box it ? Grind down the bottom edge of tail pipe to trim down? Cheers j

[Paul]

Get a pile of chain/ batteries/ water tanks, and place them around the boat front to rear, to find out if the weight needs to go forwards or backwards.  Even just moving the main battery around can have a huge impact.

[wairoacoastie]

Yea never tried going weight back but threw plenty of weight forward with no real difference.  Will try weight back ( go to the back kids) n see. Cheers

[Jeff B]

It's usually a bodge repair job on planing area that causes it, the bottom needs to be flat.
Those hulls set up similar have been hooning around for 50 years without porposing.....

[wairoacoastie]

Yea that?s my gut feeling. I didn?t run a straight edge over it , but by eye I?d say 1/2mm of ripple here n there . I haven put a straight edge  on it looking for rocker would a mm or so affect it this much?

[wairoacoastie]

Hey ya Jeff yea I think your spot on. I put a straight edge on it and right in the planing pressure are have got about 8-9 mm of rocker in it. So rather than putting wedged nozzles on witch would be a bodge repair to compensate for bodge work , I think be best to whip the motor out , flip it upside down again , and sort out the hull straightness. Bugger just put all flash new 2- pack on it too!  But as u say it had to work properly from new with existing setup , so sort out where the humans Been interfering , rather than compensating for a problem.  I might stick a noz on it also anyway just because gate steering sucks , once all sorted and everything sweet will just be selling this boat not keeping it but I won?t sell it unless it?s 100% everywhere   J

[Jeff B]

Hey Jason yeah possibly your eyeometer is slightly out of calibration haha.
Yeah it doesn't take much to upset handling, on ali boats with a ride plate it doesn't take much of a dong to create a bit of rocker and porpoise.
Be wary just grinding the glass back to make flat as you might end up with a hole or previous dodgy repair that was just glassed over.....
I takes a bit to repair fiberglass boats properly.

[wairoacoastie]

Yea mate there?s been ?extra layers ? put on the bottom , at some early stage , didn?t see any unsound or bad dings in it tho , time will tell.  Got a week of rain just started , once the settles , out with the motor n flip it over (again😭)
I?m pretty good on the glass for a Wombat  , just shoulda had attention to detail in the first place. Lesson learned?.
Amazing how it doesn?t take much n it can make a boat into a circus ride! Cant get anywhere near tapped out n it?s flying outta the water!
Will take me about three solid days plus curing to sort it n try again.
Sorry no pics I?m too tech dumb to small the file size off my phone. J

[wairoacoastie]

So yea taken a while to get to things but bought a bunch of epoxy n stuff ,flipped it over , run a straight edge over it , and worked away at quite a high area in the middle (7-8mm) gave up on the sander for a bit n got out the electric planer!   As it got close , I glued a bit of 40 grit to a 3m or so length of steel 80x40 n spent several hrs blocking it down straight.  Came up really god , no significant damage under all that just standard scrape marks. This boat hasn?t seen a lot of river use.  Painted it back up with 2 pack after checking forecast and 10 hrs later it got a bit of rain on it. Ah well it?s only the bottom. Made a ride plate to go infer the unit n set level and gave it a shot in the water. Much improved. Another 10-15 mm down angle on the ride plate and it?s pretty well dialled in. Original gate steering was the worst I?ve seen in my life and realistically dangerous.  Got a good used noz off sss eng in chch, fitted it up ( had to machine out noz diameter a bit for the extra powerful ford Granada) and it steers like a go kart. Brilliant. Good wee boat now.
And am happy to put it up for sale now. Churrr

[Ross Goldsack - JBNZ Immediate Past President]

Good to hear.
Just shows what improvements a bit of love and attention to detail can achieve.