questions about my boat and motor

[master_baiter]

i have a 14 foot elgin run about.  Not ment for fishing but i am going to turn it into one.

1.i have a 1972 johnson 50hp motor when i run 3/4 or more throttle it sounds like i am running to high of rpm's like the motor isn't getting enough water to the prop.  I useally fish allone so i have never noticed it when i have another in the boat.  The prop itself is in decent shape not new but not chewed to hell.

2.When i run the motor at 3/4 or less it plains out great but it feels like it wants to push the front of the boat into the water rather then keep it up i have nothing in the bow other then life jackets.

if u have any suggestions on these problems feel free to express them.

[DDbasser]

Sounds like the prop on your motor isn't the right pitch.  

[Yankee_Bassman]

I'm assuming you don't have power trim. If you don't, there should be a pin that goes thru the mounting bracket on the transom, which controls the tilt of the motor against the transom. There will be a series of holes in the bracket, thru which the pin can be placed. Get a friend to lift the skeg of the motor enough to take the pressure off the pin. (Don't trust the lock on the motor to keep it up; if it fails, you crush your hand if it's in the wrong place when the motor comes down.) Remove the pin, (some have a lever that flips down, some are held in with a cotter pin), and move it one hole up. This will cause the prop to be at a slightly higher angle. The bow plows deeper the lower (closer to the transom) the motor rides. Try a test ride. There should be some improvement; if it's still plowing, raise another hole, etc, etc.

If this doesn't solve the problem, get the prop checked at a prop service shop. They can tell you if the prop is correct size; on those older motors, it doesn't take much damage to create cavitation, which robs the prop of water, and thrust. Also, motors that get stored off the boat with the motor's weight on the prop for long periods can cause a "set" to occur in the prop blade, which may not be noticeable to your eye, but throws off the symmetry of the prop and again robs power.

One other problem that can cause plowing is not as common, but does happen. If the boat sat in storage for a long period of time, and wasn't properly supported, the shape of the bottom of the hull can actually change, and the boat will never ride properly again. Sometimes you can see the distortion with the boat on a trailer.

Start with the simple stuff, though, and check the motor position. Let us know how you make out.

YB

[just_another_newbe]

it could also be that the motor is too short for the boat, it makes sense that as the boat gets faster a shorter motor will not keep the prop in the water correctly, it also makes sense that with an extra person in the boat the added weight keeps the boat a little deeper in the water so it's not as noticeable. I have seen this happen when people get new boats and try to re-use a motor from they're old boat. there is a "sweet" spot for the right depth of the motor and prop for each boat. that's part of what a jacking plate does. it could also be a combination of everything mentioned in the previous posts.