correct prop set up for e-tec

[STUIE63]

probably also has alot to do with the vee of the boat Jabba's does look like a deep vee.
Stuie

[Jabba_]

Jabba, I must say it is always interesting to read what you have to say WRT setting-up outboard motors. I (like many I guess when it comes to working-out the correct installed height of a new outboard) am slightly confused by what appears outwardly by some to contradictory advice/information peddled by a majority.

My own boat (unfortunately 4000km away at the moment as I am away with work for a few months) is a 16 foot fibreglass runabout with a 90hp 2 stroke outboard swinging a 13 1/8x16P (from memory) Vengance prop installed with the cav plate around an inch or so above the bottom of the hull measured the way you have there. This has actually left a two inch gap at the top of my outboard transom mount, but I will be getting that looked at later when I get back home.

It performs well except for a tendancy to cavitate while hard conering when pushed very hard trimmed hard up in the last 1/8 of the trim range (where it will also start to pitch up and down a bit when it is light - just me on board), but to get it to cavitate like that I guess you might argue that I am abusing the engine/boat as normally I wouldn't see it given that I don't usually try and corner like a SMOC boat.

What I am trying to work out in what you've said (that the outboard you pictured was two inches too low) is just why it would be that much too low? Is it a weight consideration (looking at the pics you supplied I would envisage that the boat wouldn't be a small one to also have trim tabs fitted) that I can get away with in my instance because my hull has: A. a fairly slow hull speed (around 45mph) and B. is reasonably light (around 700kg in full fishing trim).

Thoughts?

Regards,

Dave.

PS; (forgot to mention): With that engine/prop combination it is spinning to 5500-5600rpm (right in the sweet spot for the manufacturers specs).

Firstly Ian (Finding time) and Stue are correct.. Also note the every boat is different, every motor is different and every prop is different.. So finding the sweet spot can be time consuming....

Now in regards to the pictures I posted, the boat in question is a 19ft Sea-swirl with a 3.3l 200hp E-tec, by the looks off it a 21deg dead rise..... Now if you take a look at the outer edges off the cav plate, they are below the line off the hull by approx 2"..
So in theory as the boat is cruising its cav plate is going to be under water.. Thats not good, the cav plate needs to be above the water whilst at cruise speed... So the owner is going to raise the motor 2 holes to start with then test,, and if the Cav Plate is still under the water at cruise, he is going to lift it again
Read this article for a much better explanation,, http://www.veradoclub.com/smf/index.php?topic=137.0

As for your prop cavitation while your cornering, well that is going to happen if your not trimming in your motor before you corner in... It sounds like you rig is set up spot on, 1" above is the general starting point, then you make adjustments from there. Different props can run higher in the water then others, so that need to be accounted for when fine tuning your set up.. Also the gear casing makes a difference also... Merc gear cases can usually run higher then any other brand.... The E-tec gear case is better then the old Ficths, but not as good as the Merc's....