position of prop

[deerhound]

I have just bought a second-hand speedboat it is 14ft with Evinrude 40hp 1984, the engine was fitted for the sale and is on the lowest setting on the mount ie; nearest the transom,is that the best place to start? I will be in boat most of time myself or maybe one other, also I bought new prop 113/4 x 17 aluminium and notice that when removed prop nut it was only finger tight? should the prop nut be torqued, I have a manual from 1991 wrong one was brought over from USA but can't see any torque settings for prop, many thanks JBD

 

[Silvertip]

Re: position of prop

As for engine height, it should be set so the antiventialation plate (the flat place just above the prop) is even with or slightly above the bottom of the boat. Your prop is probably correct for that engine. The prop nut should be just snugged up with a wrench so you can get a cotter pin into the slots in the nut.

 

[deerhound]

Re: position of prop

the bracket on my engine that alters the tilt?is on the setting that puts the leg of engine in nearest the transom on first hole, what roughly is best position to try, and how does one know when the position is correct, thank you for any replies, JBD

 

[ufm82]

Re: position of prop

You'll need to run the boat to determine your best hole position. If the lower unit is tucked in too far, (towards the transom), the boat will tend to plow and will be hard to plane. If it is out too far, (away from the transom) the boat will ride bow high and will porpoise badly when trying to plane. I would guess that the outboard has 4 or 5 positions for the tilt pin. I would try the second hole from the bottom and adjust from there. <br /><br /> You may have to move that pin depending on the load in the boat. As you add more weight and the boat's attitude changes you'll need to adjust your tilt angle. Power trim and tilt eliminates this hassle but it is rare on smaller outboards like yours. You can buy a hydraulic trim and tilt bracket to bolt your outboard to but they are $400-$500 as well. <br /><br />UFM82

 

[deerhound]

Re: position of prop

Many thanks UFM82, well here is what I discovered today after spending sometime under the hull? If I were to run a large straight edge along the underside of the anti-ventiation plate the straight edge would hit the hull about half way, but when I pull the engine out away from transom the line of the anti-ventilation plate at hole no 1 puts the anti- ventilation plate bang on in a straight line all the way along the keel!and the bottom of the plate is level with the bottom of the keel,is this the position? or should I come out one more hole so the engine when under power would tend to lift the front of the boat, Great help, many thanks hope you can answer this please? JBD

 

[Silvertip]

Re: position of prop

Its a trial and error process. Try it with the pin in #1 hole. If the bow does not rise slightly, try hole #2. Ideally, the propeller shaft should be parallel with the surface of the water at full speed and at that attitude, the bow should have a slight rise. With too much trim-out, the prop pushes toward the surface of the water, you get too much bow rise, and things begin to work against each other. Too much in-trim and the stern lifts, pushing the bow down again creating inefficiency. I think #2 will probably be ideal but only testing will determine that. You can even fine-tune further by adding some hard rubber tubing over the pin to create slightly more trim but less than a full hole movement of the pin.

 

[deerhound]

Re: position of prop

Fine well that will help me set it up when I get it in water, I will raise it one hole and then try it, if not I will go up one again, thank you for your help. J.B.D.