Outboard mounted too low?
Submitted by Gaffatron on Mon, 2016-10-24 13:41
hey all,
recently upgraded the dinghy (Dory 420 with 40hp 2st Mariner), taken it for a spin when the boat is up on plane seem to get a fair amount of splashing from the motor having a look it seems the motor is mounted about 40mm too low? your thoughts on the pics below? should the cavitation plate be the same height as the lower part of the keel or the same height as the bottom of the hull?
Image Upload:
marrisy
Posts: 198
Date Joined: 08/09/11
yep
If it were mine I would have the plate level with the bottom of the hull with the plate level. Marrisy.
scotto
Posts: 2470
Date Joined: 21/04/08
I agree
IK think the cav plate is generally supposed to be the same level as the keel.
the old owner (and many other dinghy owners) may have had trimming issues with it, and decided to drop the motor to attempt getting the nose to plane, etc. if it does, get a hydrofoil/trim tab for it.
little johnny
Posts: 5330
Date Joined: 04/12/11
same as above
Lift it up level where it should be.
just dhu it
Posts: 1081
Date Joined: 14/05/09
Bungs
yep inwould lift it up so the cav plate lines up with the bottom of the bungs , thats assuming you have enough engine fixing plate left to allow the lift of that much , the motor shaft may be too long for the transom
reprobait
Posts: 42
Date Joined: 14/12/11
Cav plate
Your guide stick is angled to the hull in your pictures, makes sure it is parrallel when making your adjustments for height. If you do run out of transom height, most can be modified with the addition of a 50 x 50 mm Ali RHS welded to the top of your transom.
Jmac
Posts: 65
Date Joined: 19/12/15
raise the transom
you have a long shaft outboard on a dinghy made for short shaft, only thing you can do is take dinghy to an Ali welder and get a plate welded on the back that lifts the prop to correct height.
Make sure they brace it well.
Doing this though makes the dinghy a lot more unstable when you stand and move about as it raises the weight of the motor from where it should be.
may be better putting up with it sitting low if you are not consistently in shallow water or trying to break any speed records.
cheers
JohnSorrell
Posts: 137
Date Joined: 28/07/09
Looks fine to me... This hull
Looks fine to me...
This hull is designed for a long shaft motor which is a standard length..... and the cavitation plate looks to be nice and level with the average lowest section of the boat. (except for the photo which taken looking from above)
If you lift up the motor anymore you will have problems when you turn.. the keels will create huge amounts of water turbulence during slight turns, and it will cause the engine to ventilate.. i.e. the prop will spin out when you make a slight turn and your speed will drop (since the angle of the keel chopping the water in front of the prop will create a huge amount of bubbles....)
Are you sure its not the transducer causing the water to splash up the transom? that to me looks very low ~1" too low.
Gone Fishing...
SpotHound
Posts: 439
Date Joined: 06/02/14
Mount up
Many quintrex have transoms 30-40mm to low to suit the vortex outboards ex china.
Go to chivers or the mob in Midland and you will see they always mount jap or USA based engines up
off the transom by 30-40mm to get around this.
Looks odd.
Seriously head down and look and you will see I am right !
Gaffatron
Posts: 355
Date Joined: 07/07/11
cheers for the feedback
cheers for the feedback raised it 30mm no more splashing!