Humminbird Depth Maxing out When I go over 5mph

[hazben]

Humminbird wide view on a 1652 aluminum boat w. 40hp Etec. When I try to go over 3mph the depth will max out and will not go back to normal until I turn motor off. If I put it in manual depth mode it will show the bottom to 15-20mph. But, the depth it shows will be maxed out at 600'. Taking the motor out of gear does not help the maxed out depth. I have to shutoff the motor then when I restart it is fine. I am guessing this is some type of electrical interference from the Etec? Maybe how many amps the alternator is putting out when it is above a certain rpm. The depth finder is wired directly to the battery.

 

[Scott Danforth]

most likely your transducer is mounted somewhere where the rivets in your boat are creating bubbles in front of the transducer.

 

[hazben]

I don't think it is an issue with the location of transducer. I did not have this issue with the other motor. Also when I stop and leave the motor running it still stays maxed out. Once I shutoff the motor it will start working correctly and stay working correctly till 5mph. Could it be not the 5mph causing the issue but, a certain RPM?

 

[Silvertip]

Different turbulence around the engine. Yes, - - the transducer is seeing air bubbles. Alternators di not "push" current into devices. Devices "draw" whatever current they need. It wouldn't matter if the engine has a 6 0r 60 amp alternator. Try re-routing the power lead away from other harnesses.

 

[dingbat]

Some tests to run:
1. Disconnect the transducer from the head unit and rev the motor. What does the screen do?
2. Leave the transducer disconnected and go above 5 mph. What happens to the display?
3. Reconnect the transducer, then rev the motor in neutral. What does it do?
4. How is the transducer cable routed? Check for a damaged transducer cable in the vicinity of the motor
5. How and where is the head unit grounded?
6. If you have a voltage display on the unit, what does it read when the problem starts?


Power disturbances typically don't manifest in a transducer malfunction without some sort of physical damage.

My money is on a damaged transducer/cable or a grounding problem.

 

[hazben]

I don't have a voltage display. I don't think the unit is grounded. I have it straight hooked up to the battery. The motor is also straight hooked to the battery. No wires going to the aluminum boat or fuse block. Do I need one?

​I will say there is a crack in the top side of the transducer which has been there for years. Never did seem to bother it before. Maybe it is now?

 

[dingbat]

If the unit functions, it's grounded. If it passes test 1,2 and 3, it's grounded well enough.

Power and ground issues on the incoming power typically show up in the display. Eliminating these from consideration was the purpose of test 1-3.

Most good quality transducers use individually foiled wires inside a foil wrapped sleeve all but eliminating noise coming from a undamaged transducer cable. Damaged, not so much.

When a piezo is going out (Intermittent signal from transducer) you typically get a flashing depth display. The max. depth (freeze) until you cycle the power would suggest some kind of "short" in the transducer. I'm thinking 5 mph generates just enough water pressure to force moisture into the crack.

My first try would be to epoxy the crack closed to see if that makes a difference. If not, a new transducer seems to be in order.

 

[hazben]

Thanks for the suggestions. Will epoxy the crack. I suspect it will end up being electrical. If I turn the unit on with the motor idling in neutral the depth will automatically max out. As soon as I turn motor off the depth will start indicating accurately.

 

[dingbat]

Thanks for the suggestions. Will epoxy the crack. I suspect it will end up being electrical. If I turn the unit on with the motor idling in neutral the depth will automatically max out. As soon as I turn motor off the depth will start indicating accurately.

did you do test 1-3?

 

[hazben]

did you do test 1-3?

​Will have to wait till the weekend before doing steps 1-3. It will be a bit of a pain to disconnect the transducer. I think in order to disconnect I will have to dismount the depth finder then remount it. I will most likely epoxy it tonight so it will be dry by the weekend.