ENGINES HEIGHT + X DIMENSIONS (With pictures)
 

Hey guys,

I have the boat in my workshop ready for winter works! My target is to achieve +65MPH with stability.

The boat is a 25ft Tullio Abbate with twin mercs V6 200hp Standard lower units + 23p attwood ballistic (cupped and labed).

It runs in great attitude with no porpoising but over 55MPH it develops terrible Chinewalking.

You can read all about my plan of mods and see pictures of the boat on plane here:

https://www.offshoreonly.com/forums/...ls-wanted.html

*****
In this post I want to know your opinion about the engines height, let me give you all info as possible:

Boat size: 25ft + bracket
weight: 1.300 pounds + 250 in inox. Steel + 850 engines
X dimension: 53,3”
engines distance: 22,8” (11,4” each one to the keel)
V degrees: 145º
Current height: 1,4” (cav. Plate below)
https://cimg8.ibsrv.net/gimg/www.off...2f15359b9.jpeg

Attending to the 4% calculation, the “standard height” should be 3,8” (9,65cms)

https://cimg3.ibsrv.net/gimg/www.off...3ce33797e.jpeg

Also I can add at least an other 1,9” (extra distance between cav plate and water intake.

https://cimg8.ibsrv.net/gimg/www.off...5ec777a14.jpeg

Here is a view of the bracket and engine mounts. The bracket is well built with 3,5” stern wood wall reinforced with kevlar and torsion bars.

https://cimg6.ibsrv.net/gimg/www.off...aced0cf27.jpeg

My plan is to purchase CMC 5” Vertical extensions and set the engines Cav plates 5,7” bellow.

That means 4.3” higher than now! As the jack plates are inclined, I guess the extra 5” will be a practical increase around de 4.3 needed and still the engines will be bolt in higher position.

Please I want to know your opinions and If you think my numbers are right.

My steps to fight against that chinewalk are:

1ºSteering upgrade (add rear tie bar)
2ºEngines Height adjustment.
3ºTrim Tabs (horizontal + custom keels)
4ºDevelop the surface of strakes (my first opinion is to install Roca Speed Rails)

**I will not build a pad in this boat or cut the bracket.

I know this isn't part of your plan but have you tried swapping prop rotation from your current set up?

Very interesting #Trash. Now I’m outwards rotation, 1/3 toe out.

https://cimg1.ibsrv.net/gimg/www.off...7f8fd2f63.jpeg

well the first question is did you install solid motor mounts? the stock rubber almost always lead to chine walking

Turn in is faster, carries the bow better.

Hey #BoostBross is exactly what I was discussing today at the workshop. I was shaking the lower units and they have mooovment. I’m afraid solid mounts will lead to a lot of vibrations than can damage the stern and the bracket mounts.

Also If I mount double hydraulic, the problem will be same, as there are rubber mounts between the engines and the steering arms.

As I will mount rear tie bar from head to head, I guess engines will dance together and instead of 4 rubber mounts, will be 8 on “the pack”

I was looking if there exists Teflon made mounts to find a middle point between rubbers and solids, but no find.

I’m 100% Im toe out, but the spinning always I got confused because I exactly don’t know if it is attending to to the top of the props <— —> “outwards” or to the bottom of the props —> <— “inwards”,,, it’s why I post a picture!

if someone can clarify please 🙏

where are the spray rails under the boat? You could move the engines a lot closer.
Toe out? with your props spinning out you should have toe in not out.
I think that Abatte has a 23 degree V, we always put the propshaft 5-6 cm under the boat and 10-12 mm toe in as a starting point

Turning in will lift the stern of the boat more, doesn't work often.
Also not a big fan of those props, Mercury trophy worked always best for us

You’re turning out

No turning out lifts the stern