Posted by acassidy on 07/13/19 - 8:47 PM
#1
Boat is a 1995 Whaler Outrage 24'
Outboard 2003 Yamaha 250 HPDI 30 inch shaft
Ok so I have borrowed a engine hoist from a fellow Whaler owner and about to move this motor.
1.) Motor is mounted on it highest hole and at it lowest mounting position available. The person I bought the outboard from insisted on it being mounted as low as possible. I used a straight edge 4' yard stick to get the measurements for this move.
2.) With the cavitation plate parallel to the boat bottom pad, it is 3 inches below the boat bottom.
3.) I am borrowing a engine hoist and will lift the outboard up after this weird storm system passes.
4.) 4 Holes are available and If I understand it correctly it is 3/4 inch for each hole.
5.) By this math it seems like this Yamaha is very long for this boat.
6.) The bottom of the hull is a rounded pad not a sharp V
Q1 Should I move it up two holes which is 1 1/2 inch higher making the cavitation plate closer to the bottom about 1 1/12 under the bottom?
Q2 Should I go ahead and move it up 3 holes making it at its highest position and putting the cavitation plate about 3/4 of an inch below the boat?
Q3 Does anyone have this boat with a single Yamaha and where is yours mounted?
Maybe I am measuring something wrong. Once I go to move the outboard I will measure it again to make sure.
My thoughts are that this is a heavy boat and is designed to make the outboard run deep and maybe I should embrace this fact and let it run deep and move it only 2 holes.
My prop is a 4 blade aluminum Mercury style 17" Pitch and run top speed 37 MPH at 5500 RPM. I am running this prop as I add hours to the motor after the rebuild 2 years ago. I am planning to put a 17 Mirage prop on it eventually. I have a 19" pitch Mirage but it is too much prop for this boat. I plan to test it once I move the motor up with the 4 blade prop. The lower unit is very deep while running and I know the motor needs to come up.
This motor seems to be running very strong but the prop on it now I think is too small in diameter giving me some bad efficiency. It is 14 1/2 diameter. The 15" Diameter Mirage will be much better, but again I have been using this prop to make it easier on the motor as I broke it in after the rebuild.
Sorry this is so long but I really would like to move the motor once and be done.
Thanks for any help with this.
Archie
Posted by MG56 on 07/14/19 - 10:58 AM
#3
Your boat calls for a 30" shaft, and you can check this by measuring for the hooks that go over the transom to the cav plate. When you are running you want the cavitation plate flush with the surface of the water.
I'm sorry if you want an exact answer but I would move the engine all the way up and take it for a ride. You need to get that cav plate at the proper level before you tweak the prop. If the cav is right then try the other prop you have and see what happens. I'd actually want to do a test run with the wrong prop before you change the height.
You don't exactly have a very common boat/engine combination so the more info you can derive the better.