[Fieldtester]

O.k...the subject speaks for itself. The boat is a 31' JC Casco Bay, and since I bought the boat 3 years ago, I've had an electrolosis problem. From what I know, it's been a problem from day one. Originally I was told by the original owner that none of the through hulls were bonded, causing the problem, but he fixed that. Fortunately, I have no problem with the through hulls, or the rudder. Mainly, my problem is with the prop. I have cutters on the shaft which is the only exposed part, so I have no zinc on the shaft. I do have 2 brushes on the inside bonded to the rest of the system, as is the engine block.

I also installed a galvanic isolator in the green A/C ground. I'm going to the boat next weekend to start working on this problem, and I'm looking for some help as to what to check. I plan on putting an ohm meter from the prop to the zinc on the transom to make sure I have proper grounds. My zincs are eaten away at the end of the season so I know they are working somewhat, but somewhere somethings not right. I've spoken to some people in the same marina with similar boats and they're not having a problem like me.

I've tried to research causes for my problem and have read many different things. Some say to isolate through hulls, and underwater metal; some say bond it all together. I've read that the A/C ground should be connected to the engine block, but then I also read that it's better not to do that because it isolates the A/C from the D/C.

Any recommendations would be appreciated!!

 

[oldmud]

FT, Have you thought any about maybe it's not electrolysis? Cavitation burn ? Is it mostly on the tips? Is it mostly on the low pressure side? Fwd.? Just a thought.

Don

 

[Fieldtester]

Definately, electrolosis. Just got the wheel back from the prop guy (he welded the bad spots), and he said that I would probably need a new wheel next year if I don't fix the problem.

This prop is a Michigan nibral that I just bought last year.

 

[B.Attitude]

Wait for Capt Larry to chime in or pm him.He has a 31 JC and I know he responded to this topic a few years back,you want to listen to him.
paulie

 

[Dantilu]

Field I sent you an Email through your website.....

 

[blackdiamond296]

Its not a fix to the problem but having a Nibral probably isnt helping- the addition of the softer metals is a big downside. Electrolysis was a problem at our old marina- so much so that one summer there completely destroyed a brand new Nibral!!! Went back to a regular bronze prop after that without incident.

...Like i said, not necessarily a fix, just something to keep in mind about that prop.

 

[Fieldtester]

I thought bronze was a softer metal than nibral If it is, then I would think it's more susceptible to electrolosis than the nibral!

 

[captainlarry84]

Chimming in!!!

For starters let?s break down your problem:

1. Is the problem only with the wheel?
2. If so yes Nibral will go much faster than bronze because there are three different metal in Nibral. However if you are properly bonded you should be able to use Nibral as I do with my JC.
3. For starters I would add a dyna plate at the far end of the bonding system. Your bonding system then starts at the transom zinc plate and end at the dyna plate. The dyna plate give absolute ground through water
4. Add a guppy it should hang so it opposes the wheel. The guppy should be hard mounted to the rudder post. You can snake the wire under the liner in Casco Bays.
5. Look for problem. It is important that all negative leads go to a negative bus bar. If you pick up negative from the engine block for any reason that could be your problem. Unlike cars where everything negative comes off the chassis. Not in boats the chassis AKA engine block is for ground only the green wire. I hope I am clear on this. A guy in my marina pick up negative by attaching his fuel gauge negative lead wire to the tank strap. Electrolysis was out of control.
6. When did the problem start?
7. Use a tone meter and make sure that you have continuity in the bonding system to the zinc plate. Also a rudder zinc is always a good idea,
8. Do not use that repaired wheel. If it was nibral and repaired and the fact that the shop said one more season. N/G junk it. If you throw a blade you will never get home. Plus throwing a blade under speed can really cause damage to you cutlass bearing and other running gear. Four bladders make great garden decorations along with bent anchors & broken lobster pots. That is where your wheel belongs.
9. Bronze is a fine wheel for your JC. Unless you have more at 23-24? of pitch you can use bronze. Nibral really is need when you over square the wheel and really load up the blades. On JC the Diameter does most of the work. I will est your propeller at 23 X 23 if you have approx 375 HP & 2800 RPMs. If I am close go with the bronze.
PHOTOS: #1 & #2 Idems you should invest in. #3 If you wheel looked anything like this, put it on the lawn.....!!!
#4 & #5 This is the way my bonding system looks at the busy end, note that the guppy is measure before launch to make sure it opposes the wheel. It is also checked for continuity.

Keep me posted It can be fixed.

 

[Fieldtester]

Wow, thanks for all the info Capt. Larry!!

A couple of questions:

1. I have 2 dyna plates in the hull, but I always thought they were grounding plates for electronics?!? Originally, when I bought the boat, both the electronics and the bonding system was connected to that. I thought it was wrong, so I disconnected the bonding system from those plates.

2. Isn't the engine grounded to the negative terminal of the batt.?? If so, then it too is connected to the bus bar.

3. To answer your question about when it started...from the day the boat was built!! It's worse now with the nibral though!

4. Regarding the guppy....I thought about adding one, but I don't want the thing kicking around the ****pit when I'm running. I'm assuming that it comes up from the floor somewhere and you flip it over the gunnel when dockside?!?!

5. My wheel didn't look as bad as the one in the pics. It had dimples in it which the prop guy drilled out and welded.

Here is the history on my wheel. Two years ago, I bought a new bronze wheel because the prop guy I USED to go to told me the one I had was shot due to corrosion. This is a very popular place, although it wouldn't be right for me to say who. Anyway, he sold me a wheel that he said was not a Michigan, but made by the same company that makes the wheels for Michigan. Within, 1 month of being in the water, on the way in from fishing one day, I developed a vibration in the boat. Everyone said I must have picked up a rope or something. I had the boat lifted and it turned out I had 1 blade bent!! Everyone I spoke to said I must have hit something. I've been running boats my whole life, and I would have known if I hit something I said, but everyone told me I was wrong. So I had the prop straightened. About 1 month after that, I'm heading offshore with 6 guys, full fuel, bait, etc., and I start to get a vibration again. I imediately start heading back in. (I'm about 10 miles off at this point). Th vibration gets worse, and then all of a sudden BANG!! Guess what, I lost the whole blade!! I ended up as you said, replacing cutless bearings, straightening the shaft, etc.

Again, everyone said I must have hit something. This time I fought it, knowing that there was no way I hit something. The prop guy went to the manufacturer and gave him the specs on the boat. They said he never should have sold me that prop, as there is too much weight and torque in the motor. That is when we switched to the nibral and all has been fine.

Needless to say, loosing a blade again puts a fear into me. I would really hate to have to buy ANOTHER prop again. The cost is killing me!

The prop guy I'm using now recommended I put a spacer in between the shaft and the tranny to push the shaft back exposing more underwater so that I can fit a zinc on the shaft. What do you think about that? I notice you have one on your shaft, but I have cutters which take up all the room for a zinc.

 

[captainlarry84]

More

1. I have 2 dyna plates in the hull, but I always thought they were grounding plates for electronics?!? Originally, when I bought the boat, both the electronics and the bonding system was connected to that. I thought it was wrong, so I disconnected the bonding system from those plates.

Correct they are for electronic. It is for the ground, however bonding system also need absolute ground it was correct in the being.

2. Isn't the engine grounded to the negative terminal of the batt.?? If so, then it too is connected to the bus bar.

No you should not have a direct lead from block to batter. It goes through the starter. Negative bus bars should be feed off the batteries

3. To answer your question about when it started...from the day the boat was built!! It's worse now with the nibral though!

Did is start when you took the straps off the dyna plate?

4. Regarding the guppy....I thought about adding one, but I don't want the thing kicking around the ****pit when I'm running. I'm assuming that it comes up from the floor somewhere and you flip it over the gunnel when dockside?!?!

The guppy comes up from under the liner onceunder the gunnel is a quick disconnect to it is not in the way. The guppy is great in that it tells you daily what is going on.

5. My wheel didn't look as bad as the one in the pics. It had dimples in it which the prop guy drilled out and welded.

I hope he welded with Nibral and not bronze. Few weld with Nibral. It belongs on the lawn.

Here is the history on my wheel. Two years ago, I bought a new bronze wheel because the prop guy I USED to go to told me the one I had was shot due to corrosion. This is a very popular place, although it wouldn't be right for me to say who. Anyway, he sold me a wheel that he said was not a Michigan, but made by the same company that makes the wheels for Michigan. Within, 1 month of being in the water, on the way in from fishing one day, I developed a vibration in the boat. Everyone said I must have picked up a rope or something. I had the boat lifted and it turned out I had 1 blade bent!! Everyone I spoke to said I must have hit something. I've been running boats my whole life, and I would have known if I hit something I said, but everyone told me I was wrong. So I had the prop straightened. About 1 month after that, I'm heading offshore with 6 guys, full fuel, bait, etc., and I start to get a vibration again. I imediately start heading back in. (I'm about 10 miles off at this point). Th vibration gets worse, and then all of a sudden BANG!! Guess what, I lost the whole blade!! I ended up as you said, replacing cutless bearings, straightening the shaft, etc.

Again, everyone said I must have hit something. This time I fought it, knowing that there was no way I hit something. The prop guy went to the manufacturer and gave him the specs on the boat. They said he never should have sold me that prop, as there is too much weight and torque in the motor. That is when we switched to the nibral and all has been fine.

Needless to say, loosing a blade again puts a fear into me. I would really hate to have to buy ANOTHER prop again. The cost is killing me!

The prop guy I'm using now recommended I put a spacer in between the shaft and the tranny to push the shaft back exposing more underwater so that I can fit a zinc on the shaft. What do you think about that? I notice you have one on your shaft, but I have cutters which take up all the room for a zinc.

I assume that you have at least 1.75 Shafting. The spacer in a good idea, however make sure if you put in a spacer that there is a jumper to maintain the bonding system. The spacers are all made of a non metal material. In addition you do not want too much exposed unsupported shafting never good. You may have to choose one or the other. Also the shaft zincs do not last to long due to the friction of the spining water, like belt sander they where pretty quickly. Maybe the zinc prop nut is a better way to go. It is much easier to install.
As for you wheel well first of all get a new one. Once again Bronze will be find. When ever I buy a new wheel I like to see the box it came in. The label from the factory will give you the production number and the exact size the wheel was when cased. This way you know from day one that the wheel was not re-pitched prior to purchase to fit your needs. Re pitching in never good. Bending blades weakens metal. So you want to start as close to proper as possible. On New England boats. You go max. Diameter, load with correct pitch & finally fine tune with a little cup and only a little cup if need. Cupping loads up the end of the blade. You want the whole blade to do the work and not just the edge.
These are my thoughts some may disagree..so lets hear it!

In closing it sounds like your bent wheel story from day one was a horror. What motor, gear & wheel do you have I can take a shot at your prop size using my math.

This post edited by captainlarry84 09:15 AM 02/24/2008

 

[Fieldtester]

CAT 3116 350hp
Twin Disc 1.5:1
I can't remember the prop size. I THINK it's 18X19!? I will look later today when I go to the boat.

The prop guy was welding with Nibral rods. I'll post the size of the prop later today.

 

[Fieldtester]

Still a little confused on the negative feed to the motor. If the negative lead is connected to the starter, and the starter is bolted to the motor, isn't the whole motor connected to the negative lead then??

This post edited by Fieldtester 09:57 AM 02/24/2008

 

[captainlarry84]

CAT

CAT has an Insolated starter. Meaning even though it is bolted to the motor the negative is not. Yanmar is different. I had both in my JC. I never had a problems. With the CAT I was very mindful of where to pick up negative. You can pick up negative from the CAT motor but you are really picking up ground which will act like negative can lead to electrolysis.

 

[SomedayCame]

Hey Chris,

I had the same issue last year coming back from a day offshore out of Shinne****. I felt a vibration and then "BANG". A customer onboard said he saw a piece of metal shoot up from the transom and land about 10ft back from the transom. Lifted the hatches to see if water was coming in and thank god it wasn't. While on the hard We only had 3 of 4 blades on the prop. Everyone said I hit something also but man...YOU WOULD KNOW IT IF YOU DID AT 18knts. Where the blade was missing it was the cleanest edge remaining on the hub of the wheel. My boat has been in the same slip since it's been born back in 1989, minus the one year in Shinne**** and the 2 sesons it never hit water. Our boats aren't to far apart from each other at the Marina either. The previous owner told me he had always had a problem keeping the zincs for a whole season. Not to mention the boat dosen't have any shore power either. I have a shaft zinc and a transom zinc and only having the new prop on her since June 07, it seems like it has lost it's luster.

My original thought on the old prop was that it was an old prop. maybe 10 - 15 years old. My question to "Captlarry" is do you think the age of the prop had something to do with it failing or should I look into something else?

Good Luck !!!

Brad

 

[Fieldtester]

Brad,

When mine broke, you could see that the metal "stretched" and "tore" off from the hub. It scared the **** out of me, as I too started ripping hatches open to see if I was taking on water! It sounded like a gun when off in the hull! Another problem people tell me is that it could be someone around us causing the problem which is definately a possibility!!

 

[captainlarry84]

Age

Age of a wheel has little to do with performance for the long haul. Bronze wheels do tend to weaken over time due to some blade flex. Any flexing is never good. Like bending a paper clip they weaken and snap. Re pitching is another bad move as it bends the wheel. Nibral is much harder and flex less. You can tell when wheel start to go. When you tap on them if they lose their ring you will know. The less you pitch & bend them the better. Even cupping is no bargain unless done with little or no heat. If you have to re pitch never more that 1? max after that you are looking for trouble.

 

[SomedayCame]

Old wheel...New wheel

Saved old wheel for a paperweight.

 

[captainlarry84]

Junk

The wheel photed is electrolysis for sure. Also keep in mind that all wheels have max & min shaft size borings that are recommended by the designers. Exceed shaft size limits can also weak the props at the hub. So when you selct you next wheel make sure you are with their specs. I have a 23" diameter wheel. Min shaft is 1.5 max is 2" I use a 1.75" shaft for that wheels.

Your Fortier must likely 1 3/8 shafting for a 18 to 19" wheel with a max shaft of 1.5".

This stuff can just go on and on.

This post edited by captainlarry84 12:13 PM 02/24/2008

 

[SomedayCame]

Are you saying the old wheel or the new wheel has/had the electrolosis problem??


1 3/8 shaft..17 x 18 LH with light cup..As per Ron Fortier of Fortier Boats. I can remember when the boat was brand new and during the sea-trial we tried 3 wheels due to an unknown whistle from stern area between 14 & 17 knts..Find the right wheel and the whistle was gone!

Thanks again Capt. For your words of wisdom..I know a lot but there is always room for more..

Thanks again!!

Brad

This post edited by SomedayCame 01:27 PM 02/24/2008

 

[captainlarry84]

The new wheel looks ok but hard to tell. It also looks like a bronze unit which is all you really need. Is the collar pin steel? If so change it to SS. If it is SS something could be starting.
Ron does a real fine job at things like bonding, so unless you made changes any problem you may have is most likely an outside source.
The whistling in props is usually caused by too sharp of a leading edge. Sing can be removed by lightly filing the edge a touch.
I assume that your shaft zincs were removed? Also keep in mind it is nice to get the zinc as close as possible to the wheel, however do not make it so close that it obstructs the flow of water to the cutlass bearing.
Once again look into a guppy system.