Z20 Porpoising at midrange

[Atrain89]

So got to spend some time out with my father on his 2016 Z20 with 200 Pro XS. He had a Croxton Razor 4XL on it that had great holeshot and handling. But I noticed every time it would slow down to around 4K rpm the boat would start to porpoise badly. My father said the boat has done this since he bought it. So knowing that is not a good thing I decided to swap the 24 Tempest Plus on and lower the jackplate 1". The boat then ran great on top end and had better bow lift. When I slowed to around 4K rpm it didn't porpoise but with boat waves it wanted to start to. Any suggestions as to what I could try to adjust to eliminate it from porpoising so easily. I have experienced porpoising on my Z9 but only when I'm ready to drop down off plane, not at midrange..

[hekistner]

Use the power trim to compensate for the porpoising when you slow down..

[Atrain89]

Yes but the boat shouldn't have to be trimmed all the way in at midrange speed.. that's what I had to do and it still wanted to porpoise

[Fishysam]

All the way down your saying?

[ChuckHannaford]

lower your motor on jack plate.

[Atrain89]

All the way down your saying?

yes I had trim all the way down to eliminate the porpoise

[jpalik83]

What speed are you calling midrange? I had a nitro 911 cdc that would want to porpoise at anywhere from 28-33 mph because it was wanting to fall off pad. Big ole heavy boat!

[Atrain89]

Around 40-45mph

[OldTimer57]

About the only way I know you can cause this is by poor balance. A way stern-heavy boat will do exactly this. Could be too much set-back. Some water-logged foam in the back. Too much jack plate offset. And, of course, a pad that is not flat, if such would make it past inspection at the factory which seems like a stretch to me.

[ChuckHannaford]

lower your motor on jack plate.

Not trim down, motor needs to be lowered on jack plate so prop gets better bite.

[Fishysam]

Not trim down, motor needs to be lowered on jack plate so prop gets better bite.

Need the trim as low as it goes, and I used to plane at 17mph I raised the motor 1 inch and now I can't plane lower than 27 without porpoise

[Keith6628]

I spent some time in a Z20 and was going to order one then at the last minute I went with a Z21. I noticed immediately in the Z20 that it would porpoise very easily. My Z21 will also porpoise if I don't trim it down when running at a lower speed. I have a hydraulic jack plate and what I do if I am going to be moving around at lower speeds is move my plate all the way down to "0". I think this hull's weakness is the tendency to porpoise.
I think with the flatness of the hull, very little "V" on hull lends it self to porpoising. For me personally the benefits of handling and speed just the way this Z hull runs, way out weighs the negative of the porpoise.
Ive got about 140 hours in my boat now and I never even think about a porpoise anymore. I just drive it and muscle memory takes over and does the adjustments automatically. I have no information or data that proves
these hulls have a porpoising weakness its simply my thoughts from driving them for a while now. All boat brands have some kind of weakness. The deeper "V" hulls drive and ride great but fish like crap cause they lean over so much when your fishing. You have to give to receive when it comes to boat hulls and this may be the "Z" hulls weakness. Just my thoughts

[L.Roberts]

After reading many posts about boat handling on this site ( all brands of boats), I am fully convinced that a lot of people just dont know how to drive their boat.

[Atrain89]

After reading many posts about boat handling on this site ( all brands of boats), I am fully convinced that a lot of people just dont know how to drive their boat.

well that is helpful..

[BMCD]

I agree the hull on the z20 and 21 does want to porpoise more then the z9/8. Its controllable. But at the same time the hull lifts better and rides better. I could not imagine a trophy on the z hull.

[Jig_Man]

Atrain89 I have a Z20 with a 250 Verado on it along with 4 batteries and power poles. It is very stern heavy. It has a nasty habit of wanting to porpoise. I can't even use my trim until I get over 40 mph and have to be very careful when hitting boat wakes or windy areas as like you say it will start to bounce. I have tried several settings on the jack plate and added a hole shot plate (which helped a little). I don't know of anything that will solve this problem.

[squarebilljunkie]

I drove one at dealer meeting last week and noticed a little porpoising at about half/two thirds throttle. I trimmed down some and stopped it. I don't know any bass boat immune to it at certain speeds and loads. Honestly, I don't drive them less than WOT range unless I absolutely have to. No porpoising. BTW, the Z20 was my favorite out of all the series.

[HawgSnatchin]

Anyone considered a bailey foil to help?
@squarebill-curious why you like the 20 more than 21

[5dinkbass]

Every boat will porpoise if you trim up at a lower speed.

[Wisfarmer]

If you can't run 5000 rpms it's gonna purpoise my z21 is the same way there's two ways to stop it trim down or raise jackplate otherwise it's gonna do it