Damaged Prop Causing Interference on Solix G2 DI and SI Images

[SLYDoggie]

I was perplexed by a continual gradual degradation on my SI and DI images on my Solix 15 SI+ G2. I had performed all the tweaking I could do with Sensitivity, Contrast and other image related settings but nothing seemed to remove all the background interference I was seeing. I was shocked by what was causing it.

I happened to notice that all 3 blades on my prop were badly pitted/eroded on the outer parts (pictures attached). I have no idea what caused the damage to the prop as all 3 of the anodes on my 150 Mercury Verado are in great shape. The boat is also only being used in fresh water so I doubt it is electrolysis. In any case, I changed out the prop and amazingly I'm back to perfectly clear SI and DI images. I was shocked that something like this could impact the imaging on my Solix.

Just thought I would share in case others might have a similar prop issue. Also, if anybody has any ideas on what caused this kind of damage to my prop, I would love to know that. It was a prop that I had rebuilt at a local prop repair shop several years ago and it is on a Pontoon I use for Striper trolling. I have a feeling that the repair may be at fault but am perplexed.

[Amistad Tackle]

Looks like electrolosis. Is that an aluminum prop or stainless?

[MichAngler]

Most common causes of electrolysis

Bad ground in the electrical system

Jump switch connected to the wrong trolling motor battery

give the boat a once over to see if you find any other electrolysis or discoloration in any metal that has contact with the water might help narrow it down

one possible test
if you have a volt meter with the boat out of the water and electronics, pumps and lights on test to see if you have any voltage between the prop shaft and any other metal surface
you will need some extra wire to use to reach some surfaces

if no voltage found it may be that the issue is when the big motor is running again a bad ground is most common issue

If you have water muffs for the motor to run out of the water try the same test with motor running

[1Holeshot]

Looks like an aluminum prop. I would change to stainless and see what happens.

[Bob B]

Kinda seems like the metal in the prop was able to release electrons more readily than the zinc anode .... maybe bad connection on the anode.

The interference is kinda bazaar too ..... I would agree with MichAngler to be be looking closely at the grounding.

Some of this stuff is still just FM.

[SLYDoggie]

Yes, it was an aluminum prop. I took it to a prop shop today and they said it appeared to be caused by excessive cavitation. Not sure I buy that explanation though. I will check the electrical as has been suggested just to be sure.

The Mercury Verado 150 motor has 3 anodes and none of them show any signs of electrolysis and appear to be tightly connected. I don't guess that absolutely rules electrolysis out but I would think that zinc would be "given up" before aluminum if there was an electrolysis issue.

I also already have a stainless prop arriving tomorrow and am planning to switch to it.

[MichAngler]

Cavitation is an odd but not impossible explanation for that build up

And the buildup could be creating some sort of electrical interference or vibration that affects the Solix while the motor is running

And would explain why the anodes are still good

Again very odd but not impossible

I would still do a voltage test just to be sure and provide peace of mind


One added question/note

Did you see the interference when the big motor was not running?

If so it’s defiantly a voltage/ground issue

[Wayne P.]

Cavitation is an odd but not impossible explanation for that build up

And the buildup could be creating some sort of electrical interference or vibration that affects the Solix while the motor is running

And would explain why the anodes are still good

Again very odd but not impossible

I would still do a voltage test just to be sure and provide peace of mind


One added question/note

Did you see the interference when the big motor was not running?

If so it’s defiantly a voltage/ground issue

Looks like erosion, not build-up.

[SLYDoggie]

Cavitation is an odd but not impossible explanation for that build up

And the buildup could be creating some sort of electrical interference or vibration that affects the Solix while the motor is running

And would explain why the anodes are still good


Again very odd but not impossible

I would still do a voltage test just to be sure and provide peace of mind

One added question/note

Did you see the interference when the big motor was not running?

If so it’s defiantly a voltage/ground issue

It is definitely erosion and not buildup on the prop.

To answer your question about the interference. No, I didn't see it when the motor was not running nor when it was running but idling in neutral. I only saw it when in gear and in motion... Both at 1.8 to 2.8 MPH trolling speeds as well as 6 - 10 MPH when scouting for schools of Stripers. All the interference went away when I replaced the damaged prop with a new Aluminum prop. This is what leads me to believe it isn't some kind of electrical interference. It is definitely something created by the prop itself... maybe from additional cavitation because of the erosion. The real question that is puzzling me is what caused the erosion. That is where the electrolysis idea came in.

By the way, I actually bought this pontoon specifically for trolling and with SI in mind. The motor actually sits behind the pontoons so the SI transducer has a clear view of both sides of the boat when installed on the driver's side toons. Many of the Pontoon boats aren't built this way and you would need to mount separate transducers on each of the outside toons for right and left capability.

My new Stainless Prop is arriving today and I'll be installing it before my next outing so I'm keeping my fingers crossed that it also doesn't introduce the interference I saw with the damaged prop.

[cards21]

Did you feel any vibration when it was in gear? I would think that could affect DI and SI quality.

[CRAWFW]

Cavitation on an impeller in a centrifugal pump causes the water to boil. I suspect it’s the same for a prop. It causes the same damage to a pump impeller. Seen it many times.

[SLYDoggie]

Did you feel any vibration when it was in gear? I would think that could affect DI and SI quality.

No real vibration that I could tell.

[SLYDoggie]

Cavitation on an impeller in a centrifugal pump causes the water to boil. I suspect it’s the same for a prop. It causes the same damage to a pump impeller. Seen it many times.

Thanks for the feedback.

[SLYDoggie]

I replaced the new 13 Pitch aluminum prop with the new 13 Pitch Stainless prop. Neither the new Aluminum replacement prop nor the new Stainless replacement prop caused the interference I saw with the original damaged 12 Pitch Aluminum prop. I really like the Stainless prop and will probably keep it on the boat. It seems to cut through the water much better.

I have the Mercury "Troll Control" on the boat which allows me to make very fine adjustments in idle speed from 550 RPM to 1,250 RPM while trolling. With the original 12 Pitch prop at the 550 RPM setting, I could get down to a 1.8 MPH which came in handy when night trolling for Stripers. With the 13 Pitch Stainless prop at that same 550 RPM setting, I can only get down to 2.2 MPH. I think I can live with that minimum speed for night trolling.

The interference caused by the bad prop is still a bit of a mystery but I'm going to assume it was cavitation. I'll keep a watch on the Stainless prop but hopefully the harder material won't give me any problems.

[Bob B]

It is always good to see a problem like this resolved ..... this situation kinda shines a light on the WIDE range of things that can cause interference.