OotB: Sorry I dare not answer that one. I can only give the input about my experience. It is a bit of work to install one. If you are willing to take it back off if it does not work, it cannot hurt to try it. The only thing is you will have to buy new trim cyl rods. You have to cut the old ones and weld in extensions as part of the installation.
My application was quite a bit different.
I was turning a blueprinted 27 pitch mirage prop, the Alpha SS outdrive ratio is 1.3:1 and the engine RPM was 5,200. It would GPS at 93 MPH. Not bad for a blown small block Chevy with one carb.
My 21 footer was their factory demo boat at one time. It has the kevlar option. It is light as a feather. Hard to compare with a larger boat.
Well, I think the first thing I am going to do is try a new prop. My mechanic swears by the 4-blade hydromotive. He has test props so I think I will try a few pitches and see how they affect performance and handling. If I do a stern jack I won't be installing it myself so I need to be sure that is what I want to do. I shredded my coupler this summer and am still reeling from the cost of repairs. But, being in the Midwest, it will be a few months before I am back in action.
I had a SternJack in conjunction with an Alpha SS on my last boat (18' Python Vyper which is similar to the 18 Donzi Classic) and the SternJack made a very big improvement in handling and added a few miles an hour top end. The SternJack all but eliminated chine walking at top speed (just under 80 w/built 383 cu.in. smallblock). I could drive with two fingers, whereas before, it was all hands on deck to keep the boat stable. The other variable is the prop. I found best top speed with a Mercury Lab Finished 25" Laser II, but it porpoised at midrange. I tried Mirages and Hydromotives, but the surprising winner was a Turbo Vector 25". Its blade shape and diameter is similar to a Mirage, but the handling was amazing. With this prop I only adjusted the trim tabs when I wanted a full speed run, otherwise I didn't touch them, and trim angle was likewise totally forgiving. Never a problem with blowout or turning either. My boat was much smaller than yours, but thought my experience would be interesting. One last thing, driving in rough water with the SternJack is also much safer. The prop hardly breaks free and the landings were better. The boat acted like it was at least a foot longer. Granted, the Alpha SS drive is approximately 2 1/2" shorter so the drive is naturally very high.
What about the claims that the added length of the drive with a stern jack puts undue stress on the transom. Those of you that have installed the Land & Sea Jack, did any of your mechanics say anything about this?
My concern wasn't with the transom but with the gimbal bearings and the steering. My solution was to add a Drew Marine steering stabilizer which is a form of shock absorber. I didn't observe any difference in handling, nor did I expect any. I was only seeking additional relief for these bearings and the peace of mind that came from knowing shock loads from going over wakes were being absorbed by more than the drive and the short tiller arm on the steering. If I had gone all the way, I would have installed hydraulic steering, but felt the steering stabilizer was sufficient. I trusted Land & Sea on this one.
Hey, all Donzi classic and knock -offs--a QUESTION.
Donzi 18' classic the best boat to go 80 mph in a stiff chop?
How much slower with full versas empty fuel tank?
Same two questions for you 22' owners.
Thank you very much.
I found a light wind chop was best for top speed. The 24 degree hull is terrific for taming rough water but not at my 79-80 mph top speed. I never ran a comparison between full vs. empty gas tank. My speed runs were typically with about half a tank.
Thanks for your honest info. How about anyone else?
After I bought my sternjack I was informed
in the instructions that they recommend a
high performance gimbal ring. I Don't
remember the cost. It was not cheap. Just
something to check out. Hope this helps.
Slowride
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