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[colin-stevens]

got in a bit of a thinking spiral, getting no where. puting a pair of outboards on to a RIB. now, with luck, the thing will shift, and again with luck the nose will rise up. question is, which way do i the outboards need to go to level her out? cant seem to attach an drawing, but would the prop need to angle forwards, or backwards to bring the bow down, if that makes sense
colin

[HS93 (RIP)]

From what I can remember I had a Fuji out board and if you take a line through the boss of the prop as if it has a prop shaft that wants t stay parallel to the surface of the water, if not it will push the back down or lift it up.. (as far as I can remember but it was a long time ago)

Peter

[bogstandard]

To bring the bow up have the props as though they want to push water to the surface.
To go bow down, have props trying to push water deeper.
They will only be V-E-R-Y small adjustments

John

[mike_victoriabc]

Have a look at these outboards -
http://www.safeboats.com
Gives you an idea.

[phillnjack2]

aha atlast i can talk about something that i know a lot about  ha ha .
what you want to know is do you trim in or do you trim out.

Ok for a start off you want the plate above the prop to be slightly higher than the bottom of the boat.
this is known as cavitation plate, but is infact an anti-cavitation plate. this should run on top of the water when running on the plane.
Or you will create a lot of unwanted drag and also problems when cornering.
Once you have the height right you then test the boat with the propshaft running level with the underneath of the boat.
to do this simply place a long piece of wood or plastic under the boat and check if propshaft is level with this.


on a model boat i would run the propshafts parralel to the hull bottom at first as this should give best performance.
i would sooner move weight around in the boat to attain the best attitude for model when at full throttle rather than
move the engine trim.
what you will also find if the engine is put on the boat too low is that water from the engine leg will run up into the
back of the boat in a sort of spray fashion.
Do not think the transom is the straight edge to trim motor by, its the bottom of the hull.
on full size outboards just 5 degree's can be a big difference in trim....!!!!


hope this helps a bit

phill