Gentlemen, I have a brand new red 2020 Donzi 22 Classic. Been lurking for a long time and probably reopening a 22 Classic issue.

My 1973 Corsican was point to shoot. This 22 is a bronco. It has the X Drive and 430 HP 8.2L HO MAG with cats. The manifolds weigh 125 each side so I am sure to have an aft CG compared to the earlier boats. In 2021, I tried a Rev 4 26P from BBlades and it was worse than my Bravo 26P. Flying/driving with tabs was the trick. However, this was the last time I went out in the boat as I need to make more changes.

My future goal is to pull this engine and do a 520 later to get rid of the heavy cat manifolds, but for now, trying to do something with this existing hull and 430 HO MAG motor that will also be beneficial later with a 520, full hydraulic steering, labbed prop, and possibly 280 K-Planes.

Here is my question, What distance from hull bottom to prop shaft is the ball park number for the Classic 22’?



I have searched till infinity. ALL performance boat sites. Some of the noted comments from the experts are: Teague says 4-5“. Bobby Moore recommended 4.5 to 6”. (However, they were probably addressing more toward straight V’s.) AI says 3-5” on the 22 Classics. So, 5” seems to be a safe and effective median.



I know all Donzi 22 boats/hulls can vary. All have their anomalies. Just looking for a rough order magnitude number to help in purchasing a new lower, IMCO or XR Sportmaster, for the rounded 22 Classic. A very knowledgeable racing background/prep source helped me by recommending a -2” Drive on the Classic 22’s. He also said that this is probably the most important change I can make. Most everyone else says the same with earlier Classic 22’ boats. However, depending on the vintage, the factory “X” resultant bottom to shaft distance can vary. For instance, if the earlier factory X resulted in a 7” ish below bottom, then 7”-2” = 5”.

When I mentioned that am already at 6.5 inches, he said to still go with the -2” drive. He said, “At 6.5”, I am buried.” He is suggesting this change will help significantly with the porpoising issue.

However, in my thoughts, 6.5”- 2” = 4.5” and I am a bit concerned about it being too high and I do not need the drama of any additional difficulties of trick props and “hard to plane” drama issues. I did not want to press the issue as he has already taken two phone calls from me and I do not want to bother him. Going to the Forum to cross-check experience from long time 22 Classic owners. Later, I may drive the boat up to him and have him evaluate. Controllability, comfort, and drivability is priority.

In closing, I am reluctant to go below 5” as one other person with a 22 had problems below 5”. As a note, with the 22 hulls being rounded at the bottom, the water off the back of the hull when entering the prop is not as pronounced as with a straight V.

I have read the Thirdchildhood, snave8, Pat Mcpherson, Tom A, Yeller, roadtripse, and many others with appreciation.

Any further thoughts, considerations and advice on dimension and off the shelf prop are much appreciated?

Have you tried a mirage plus three blade? Sounds like you’re having stern lift issues

No I have not. The only other prop I have tried was the Rev 4 and this was a recommendation from both the Donzi Forums and BBlades.
I seem to think I need more than a prop. It was recommended to raise the drive. I am just not trying to go to high.

Not a 22 Donzi guy, but 4.5" below the bottom is not really high and you shouldn't have any issues getting on plane or carrying the bow. Besides that, you can always add a drive spacer to bring it down a 1/2" or more.

They had the drive height right in 1987. It was 1 year only, 1 inch higher and I think the same as the shelby that came way later. With that said it depends....

The slower speeds (under 70) like a cleaver. Higher speeds like a lot of cup. It depends on your goal... some guys want nothing but top end, others all around, others just want an easy ride so opinions vary vastly based on who is in the seat AND where and how the boat is used. I believe thirdchildhood ran his balls out in fresh water. I know MANY others that probably would hate his setup because they like to cruise mostly. I've been on donzi runs where some guys never really went under 70MPH and others are just chilling at 45. Those are very different use cases. Most of the guys posting are the ones going balls out.

IMO props are #1. You can change the entire feel of the boat with just that and you can likely borrow some for testing... once you get close to what you like get one made/labbed. If you change drive height you have to reset and do prop testing all over. I think everyone you mentioned had custom prop work done to make the boat 'right' for their own personality. A stock bravo 1 I don't think really ever works. Mirage plus or a cupped B1 is a good place to start. Some swear by the turbo 1 but I never personally tried it. My brother liked a qiv1 for all around but for top end mirage plus (iirc labbed with more cup). I like more blades for easy planing and good mid range most of the time but I boat in salt that gets sloppy. There are far more people that own 22s that never changed drive height that dial it in with a new prop than the tiny few who make wholesale changes to the setup

For what its worth, I gave you real world experience when you called last week. We have installed -2 IMCOs on dozens of 22s with the same issue and it helps tremendously. I wasn't guessing...
And as mentioned above and to mimic what I also said to you on the phone, you can always add a spacer.
Real tabs will help too. Its not the weight of your engine causing your problem. The 502 mag boats handled great. Iron heads, cast exhaust, they probably weighed the same as your engine if not more.
Id still bet its your best route. Its a great boat, good luck with her.

Gentlemen, I appreciate the insight and follow up.

Johnny, thank you again!
Your guidance is worth a a lot!

R/

Standard Bravo One drive works good at a 17 1/4" X-dimension.

I measured mine several years ago. But I am out of town now and I do not want to put out a bad number on the forum for a Factory new 2020 Classic 22

I know data may show up later on this forum when a person may be doing a search for knowledge and looking for reference.
When I get back after the holidays I will double check both the 1) X on my 2020 and 2) Keel to prop shaft.

It would be nice to know keel to prop shaft on the Shelby 22 Classics as they are often referenced as working well, but I have never seen an actual number to compare.

I will offer this concept for the time being. River Dave put out a drawing to explain "X" and with a 14 degree transom angle he had a 16 1/2" "X" and a 5 3/4" keel to prop shaft "NOT TO SCALE BRAVO 1 Drawing".

Reverse engineering, using his drawing, a 17 3/4 "X" would be raising the "X" 3/4" and reducing the shaft to keel to 5" which seems to be conservative number for the "V"'s.

When I purchase a lower I do not want to have to use a spacer to adjust depth as I went a clean look.

Thanks Ed

My brother has an 87 that we fully restored in 2019 X-Dimension is perfect. We run a 25” rev4 and it performs flawlessly in all conditions. We helped a customer a few years ago with a 496 HO Shelby, came with a 25 mirage plus, if you weren’t wide open it would porpoise uncontrollably. A 25” Rev 4 made it a completely different boat.