Prop diameter?

[Toffen]

Hi!

I have bought two Merc 2.5 EFI engines (SVS and PCU) with 15 inch midsections. The engines will be mounted 18,5-19 inches senter to senter.

I have been reccommended by some to mount the engines with the propshaft 1 inch below the bottom, and by others to mount them even - 1 inch above the bottom. Merc Hi Performance reccommends 0,25 below the bottom with the Sportmaster lower unit at 90 mph.

With the 15 inch midsection the propshaft will be approx. 0,5 inch below the bottom with the engines mounted all way down.

If it proves to be a little high (expecially at cruise), is it possible to compensate with larger diameter props?

I plan to use Bravo 1 props 28 inch for cruise and Chopper II 28 inch props for wot. I will also try Mercury ET props for wot.

Boat rigging starts in 4 weeks! Can't believe it soon spring again.

Enclosed a picture of a twin Merc 2.5 rigged Phantom 25 with 6 inch setback. I will only use 1 inch setback due to overall balance.

Cheeers, Toffen G :rolleyes:

[Liquid Force]

Hi Toffen,

Your are in a similar position to me, Im just about to hang a pair of 300PM on a 21ft Deep Vee, also 15in shaft and am trying to work out what height they should be set at to start with as I won't be running jackplates.

My concern is with your engines so close do you envisage the motors provding turbulent water to each other's prop?, I know from handleing point of view the closer the better but it may have effect.

The photo of the boat you show sems to have the propshaft above the pad but quite away, but it's hard to tell just from a photo.

James

[fastercat]

get the jack plates manual or power then you can dial it in just my two cents that is what i have :D

[150aintenuff]

use a 2" jack plate.. and use the plate to adjust the height. and the .5 below is a good place to start..