The trim limits either are defective or not set properly. They have two limits. One limits the height for trim while running; the other is for the max up for trailering.
You should have a rocker switch that is labled "trailer".
That should bring drive all the way up. Also could be defective switch.
If your boat is a salt water boat. You will experience niggly electrical things.
Cheers
Stew

Thanks Stew! Tried to call the other day but the signal was busy. Waiting on the prop guy to tell me what they look like and hoping get a fix.

Ok. Does your phone number end in 9740? If so I'll call you tomorrow.
A few years ago I bought a complete dash panel from Donzi direct because you can't buy the style of Livorsi gauges anymore.
If you need anything let me know

No sir, my number 437-1733 in the seven O four area code. Im thinking about replacing the gauges with vesselview or something similar.

Big blocks were supposededly tested by the factory and sucked. Weight was the issue. Whipples will fix the power issue on small blocks.

Our boats have a pad in the back so chine walk shouldn't be an issue with the right props.

Mirage plus are the fastest but pretty bad for planing and cruising.

Thank you. I've heard that about the big blocks but haven't been able to verify it. I don't know if it's folk lore or truth. The difference in weight is 600lb total. About the weight of four adults across the back seat. I can't imagine it would make that much difference.
I had a Z29 I put 502 with bravos in. It's a very light boat and was quite the weapon. But handled the power.
Do you have much experience with whipples?

I don't have personal experience with whipples but I know they have been used on the 28 hull successfully. There is a whippled scorpion running low 100's. For our boats I'd personally prefer a centrifugal setup (i.e. procharger) because we really don't need the area under the curve increased that much down low. However based upon what everyone and their brother is stating for the last few years procharger's packaging doesn't hold a candle to Whipple. Everyone has told me to go whipple hands down. The Scorpion boat that was whippled had a reported power of 550 per side, the 6.2 mpi goes up to 500 per side because of the lower compression. The 350 Mag gets up to 450 which is pretty respectable.

I think the weight issue with the big blocks is just a straw on the camel's back issue. The 28 hull, from the rub rail down, is the same as the 27 ZX hull. It was built for a single big block and there are a few 27's out there with big power running very well. So it went from an engine in the 1200 pound range to a pair at 1700 ish pounds. Bump that again to 2400 pounds and the bottom gets too far out of balance.

I would highly recommend the whipples if you have extra $$$ around and need to stay in a 28' boat, but if you're looking to make your 28zx run 90+, spend your money on a bigger boat. I don't think I'm the only owner of a whippled scorpion, but I can tell you that pushing the 28zx (twin step) over 80 becomes a handful and not something easily done. The claim that the 377's whippled can break 100, not sure who threw it out there, but I have only been able to push mine to 84 with 5psi of boost. I'm sure I could get a few more mph out of her but there's never calm enough water with long enough runs to get her there. And I'm sure a tune could help get more power too, but again, it comes back to the hull and IMO a 28'zx isn't made to go above 80. She can run all day in the mid 70's, but if you want 80+...look at the 35ZR. That's where I am at now.

Thank you all for your reply. Goal is to run high 70's comfortably. The 28 is the perfect size for where I boat. As much as I aspire to a 35ZR I have too much going on to warrant the expense with a lousy Cdn dollar.
My buddy had a 28 with Holley blowers. His sun races in F1 He's a great driver. and could hardly hang on to the 28 at 80+ as you've said.
Im assuming you've had a good experience with the whipple chargers??
i just want a little more go. Wife says it's fine. She has two engineering degrees and still doesn't get the hp thing.
Again. Thank you all for your input. Much appreciated.

I bought mine in the winter of 2015, had to replace a blower in 2016, but no other issues....yet. That expense was enough for a few years if you ask me.