Steering question on 1974 20ft CC SF

[foolharty]

If you aren't using the bow to break waves in a headsea, the motor should be trimmed up. Look at the wake and trim up until the bubble or v is gone. Ideally the water will look like its coming off the bottom of the boat perfectly. Getting as much of the length of the boat out of the water at cruise is key. Saves gas, easier on motor, faster. I don't know if this is common knowledge or not as I see it waaaaay too often.

[fly4navy]

Only able to get max 5000 rpm at WOT.
Max speed is 28 its.

Prop is a 12 7/8 X 15 Viper.

[FishStretcher]

I would think you could get 30kts, or 29.5? Raising the motor 1 hole was good for 300-400 RPM for me. (6000 redline, 1:2.31 gearcase ratio) It slightly helped steering effort, too. I can pull about 28.5 kts with a F100 on a light 20' Master Angler. 13" x 15" pitch 4 blade aluminum stern lifting prop to heave a 4 stroke + 4 stroke kicker up out of the water. Rest of the boat is light- 20 gallon tank, no T-top, no live well. Empty cooler, aluminum anchor. Batteries under console.

[FishStretcher]

Prop is a SOLAS Amita 4

[Bushwacker]

Originally Posted by fly4navy

Only able to get max 5000 rpm at WOT.
Max speed is 28 its.

Prop is a 12 7/8 X 15 Viper.

My old 1975 115, that was really only about 100 hp at the prop, used to spin an OMC 13 3/4 x 15P 3B SST prop up to 5500 rpm. Your motor is about 120-125 hp at the prop, so I suspect motor is mounted too low if you can't spin that small prop any faster than that. You should be able to clearly see the top of the AV plate above the water when you're up on plane and motor is fully trimmed out to a point just before it starts to cavitate.

All motors are harder to steer when you trim them in towards the transom. You can adjust the trim tab aft of the prop to offset that prop torque effect.

[eggsuckindog]

motor is mounted too low, as Denny said creating both problems, thats why the dealer said trim it up but thats not the real issue he should have mounted it higher - cav plate should be 1 1/2" to 2" above the hull bottom with that prop its a good prop - not exact as each hole is 3/4" but at least 1 1/2. you can measure it with any straight edge, wood or PVC

[mrobertson]

i agree - motor mounted too low

i used to have a maycraft 19 cc with a 4 stroke that came with straight cable steering (not a NFB). If the engine was all the way down when you took off you could FEEL the torque of the engine and if you let go of the wheel the boat would turn almost instantly. While running, if you trimmed the engine until the cav plate came out of the water, you could feel that torque just release from the steering wheel.

Moved engine up, 100% better..........added in a NFB helm and problem completely gone.


If you have a teleflex cable steering, you can actually just get the NFB helm and swap them easily. The old cable will go right back into the new helm.