Another cavitation plate hgt question

[thehermit]

Hello gang...getting ready to hang my engine on the newly refreshed 25" transom. OK have searched the site and I see the general rule of thumb is mount anti cav plate 1" up off bottom of the keel. My question is more about trim angle. When setting up your 1" above keel do you trim the motor to align with the bottom of the hull?? OR is this diff not significant? I plan on using a jig to set the holes up on the boat. Comments and epinions welcome.
Thanks

[NoBones]

Length of boat ?, Horsepower and make of motor ?, Trim tabs
yes or no ?, Pitch and size of prop ?, All of these factors play into where you want to mount the engine....
My 20 SF is 2 inches trimmed out to the bottom of the keel.
Have 24 inch Bennett's, with a 21 inch Laser II prop.
Tops out above 61mph with half tank of fuel (80 gal. top)
Keep in mind my 200HP Merc has been gone through from top to bottom. Boysen reeds, shaved heads, ported and polished intakes etc, etc. Let us know, we can take it from there.
See ya, Ken

[thehermit]

Thanks Ken,

My boat is a 1970 20' SF.....2 stroke Yamaha 130hp 13x19 stainless prop. No Tabs (yet).

When you tuck the motor all of the way in (bottom out trim) what is the measurement? This is how my jig will be setup to transfer holes to drill etc.
Thanks

[NoBones]

Start with the anti cavitation plate level with the bottom of the boat. Then start with about 1 inch above the bottom of the boat with the plate. If you do not "blow-out" on your hole shot, try to move up another notch. It is a trial and error thing till you find the right combo.
Also if your batteries are in the console that will determine the max height you will be able to raise the motor. Be carefull not to get to high that you will not be able to pick-up water at WOT.
Good luck and keep us posted, Ken

[eggsuckindog]

Take it high and if it blows out get a prop with more rake

[thehermit]

Thanks gang. I followed the No Bones lead and another CSC'r sent me this thread (and more help)

[url=http://www.classicseacraft.com/forum/showflat.php?Cat=&Board=UBB1&Number=49543&Forum=]http://www.classicseacraft.com/forum/showflat.php?Cat=&Board=UBB1&Number=49543&Forum=[/url

I made a jig of the motor bracket/cav plate out of some extra plywood. The bottom of the jig represented the cav plate and was 6" wide. I was able to hold it up to the boat and transfer all of the holes. I then pulled some additional measurements to hole centers before drilling the new transom . I think it worked out but I let you know when it gets wet. Its been a re-hab marathon (slow pace) for me. I have adjustment available up and down when I get to that point.


Cheers!

[dcobbett]

John,
Looks great!
Where did you get the "SeaCraft" reinforcing plate?

[1bayouboy]

No kidding about that plate....I need two...

[thehermit]

Dan,

Just another late night random ebay purchase
It looks cool and is functional too.