Can you elaborate on perma trim?
1st pic that plate bolted on to the cavitation plate under the water
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From factory manufactures do not put holes in the cavitation plate to fit the after market permatrims.. they do not produce or sell them, and if bolted on it voids warrentees
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They are used when a boat is slow to go over the bow wave and get on the plane,
And/or the boat tends to sit with the bow up in the air excessively when getting over the the bow wave
And/ or when on the plane the bow is in the air.
I don't know much about boats
OK
This is assuming the person at the helm knows when at rest, trim right down
, move throttle forward, boat then clibs over the bow wave very easy, once on the plane then trim up... Listen to the engine.. there is a point that you will hear air being sucked into the prop.. trim down slightly, goes way.. The other thing to watch is the bow bouncing too easy, called porpoising
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you trim down so you dont have ventation and just before porposing
As your speed increase you can increase the trim
You will find at reasonable speeds, got to cross a wake.. line up about 90 deg to the wave, just before hit it, trim down.. once over trim up again..rather than adjusting throttle all the time.
Very basically, when a hull is on the plane, its about the total weight of the boat on the water, and the hp ....and enough reserve hp at any given rpm , espec in the low to high cruise rpm range, that when hit a wave/ chop, engine uses that hp to go thru without falling off the plane and/ or have to work the throttle.
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Generally on 5 to 6.5m boats this result in a WoT speed in the low 40 /45mph range.
Im would estimate with 115 on the back normal full load/ ppl etc you can hit at least the mid 40 mph rather easy, engine right height etc.
Back to permatrim:
Under powered boat put the bow up and stern down, slow to get over bow wave etc..If min powered, this is usually fixed by changing the rake (the angle the prop blades lean back) of the prop assuming the diam and pitch are at least ball park correct, and engine height correct.
Instead ppl do a patch fix by adding a permatrim that is a hydrofoil that lifts to the cavitaion plate, and brings the bow down. It also adds load on the power head and extra drag on the leg.
Im not sure if its 20 or 25'' i will have to measure up,
Also have a good 1m or so straight edge when go to measure...engine about 10 to 12 deg angle from the transom.. much the same as boat level, engine vertical ...
Lay the straight edge along the bottom of the hull, next to the keel, out to the motor. The cavatation plate should be ion that plane or no more than 1/2" above.
While there, look at the prop, there will be something like 13 1/2 X 19 on the hub , and a part number stamped on the prop...
Sry Smudge another long post..
But hope it explains a few things helps SB out.