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To return to my question, is there any perceived benefit to drying the area around the bolts and under the washers, then applying some bedding (perhaps MainSail's butyl) to keep water and chloride ions out of the crevices? It might also provide enough lubrication to avoid scraping away the passivation layer. Both, taken together, might inhibit crevice corrosion.  Any reason why this would be a bad idea?

FWIW, my SuperLube is a totally different product, their "Synthetic Grease" meant for lubricating. It also has PTFE. I bought it to lubricate the steering chain on my C250, and then inherited a second tube that the PO of my current boat left behind.

To add to the knowledge base here, I exchanged a private message today with Drew Fry, who did the 2010 corrosion testing for Practical Sailor:

Hi Drew,

I need to replace my float switch. It's going to require splicing with a heat-sealed butt connector in the bilge, and I want to make sure I minimize any possible corrosion. I've ordered some NO-OX-ID for general use around the boat, and am also considering some lower viscosity penetrating spray for other hard-to-reach places (unrelated to the splices).

I know that you were heavily involved in the Practical Sailor testing of anti-corrosives in 2010, so would value your recommendations, In particular, I am curious about why the TC-11 that was so highly rated in 2007 was not included in your testing in 2010. Has there been a formulation change or something else affecting efficacy or availability?

What products do you currently use for various anti-corrosion needs?

Thanks,

Rick Sonntag
Swarthmore, PA
s/v "Breakin' Away" in Rock Hall MD
---End Quote---
No particular reason, TC-11 simply was not included. I have no reason to think it isn't very good. As for spray, I've been using Corrosion Block. They also make a grease which is pretty good, though not as good as...

Green Grease. Actually, there is a new set of grease tests coming out soon in PS, and Green Grease (omni lubes--they have it at Advanced Autoparts) seems even better, although No-Ox-Id is still very good. Thee will also be an article coming out showing that conductive greases that contain metals actually increase corrosion, compared with plain grease. Dissimilar metals, it seems, never help.

So long as you use a properly adjusted ratchet crimper (test pulling the wire out, hard--something should break) grease is not needed.

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I did not realize that Catalina finished the bilge with gelcoat. I thought it was just paint over top the fiberglass layup. I also did not realize that they would do this after the washers and nuts were tightened onto the keel bolts. I sort of thought that they would finish all fiberglass work in the keel sump first, then bolt on the keel.

I don't really see any signs of gelcoat on top of my washers.

The washer for my front-most keel bolt has some brown rust on it, but the washer can't be removed because of interference from the drain scupper that sticks out over it. I tried some CLR on it, but the best I could do was to go in with a toilet brush, and the CLR did not take much off. I can barely squeeze my hand down there (but getting it out is real rough on my skin), so I might be able to get some sandpaper on it. I could also lift the washer up partway to dry underneath it and possibly apply some bedding compound.

So to return to my question, is there any perceived benefit to drying the area around the bolts and under the washers, then applying some bedding (perhaps MainSail's butyl) to keep water out of the crevices? Any reason why this would be a bad idea?

OK, I now have three new nuts, as well as lock washers and flat washers. Although the front-most nut is clearly the worst, there are a couple of others that are starting to show erosion in spots, and the lock washers underneath also look bad. So I'll use all three.

My question is on what else to do. Is there any reason to try to make things water-tight, perhaps with butyl tape bedding? My bilge is 100% dry on the hard, and mostly dry afloat, except for the occasional air conditioner drainage in the front compartment, and packing gland water in the aft compartment. Is there some benefit to preventing water from getting into the crevices between bolts, nuts, and washers? Currently there appears to be no bedding present.

By the way, I'm curious why the front-most nut corroded worse than the others. It is exposed to ion-free condensate water, and I wonder if the limited solubility of metal ions caused a gradual erosion in the nut and washers. It's ironic that deionized water could be more corrosive than water with a small amount of ions, but I have stainless steel cooling baths in my lab with manufacturers' warnings not to fill them up with deionized water for this very reason.

If stuff is wicking through ends that were cracked by over-tightening, then you definitely need to replace the hoses.

A little bleach solution left overnight can fix a lot of odor problems. Peggie Hall has a recipe that's used for freshwater systems, and I'd expect it to be effective in your shower drain and refrigerator drain also:

http://trudelutt.com/linker/phall_freshwater.pdf

You might do this before replacing your hoses. At the very least, it might make the work environment a little more pleasant by killing the odors before you start to pull things apart.

Braided hoses, as a general rule, should be no more prone to leakage than other hoses.

It's especially rare for drain hoses to leak, since they are never under any significant pressure if used properly. Which begs the question of whether you're somehow dead-heading your shower sump pump, and the resulting pressure is causing the leak. If there is a check valve, is it stuck closed? Are all valves in the path open when pumping? (Both the through hull and the in-line valve that separates the shower sump from the refrigerator drain.)

Regarding the latter, note that the way my boat is piped, the shower sump pump does not pump properly unless the refrigerator drain valve is closed at the same time the shower drain valve is open. It's possible that different boats are valved differently.

I have SuperLube and Tef-Gel for preventing corrosion between dissimilar metals (SS screws in aluminum mast, etc.). But neither of these were designed for electrical applications AFAIK.

The December 2010 issue of Practical Sailor shows pretty clearly that NO-OX-ID is probably the most effective for electrical connections. (Although they don't say, it is clear from the description that they used the "A Special" formulation which is conductive.) I have ordered some for some rewiring that I need to do, but haven't received it yet. Since it is conductive, so should only be used in contact areas like battery terminals, ring connectors, and inside butt connectors. It should not be used on multi-pin connectors where it could cause short circuiting. For those sorts of things, a dielectric grease is best.

Also steer clear using any dielectric grease on antenna connections, since dielectric properties can change at high frequencies.

One quick question to get me going on my replacement:

I need to enlarge the hole for the GX2150 radio. I've managed to avoid cutting fiberglass for many years, so I know little about how to do it. What is the best tool? Manual coping saw? (I have one, but it may be too wide to fit.) HarborFreight electric Multi-tool? (Just bought one under Ken's direction, but have never used it.) Sawzall reciprocating saw? (Don't have one, and think they're scary looking suckers.) Something else?

Thanks for all the advice. I may have never tried just pulling out the radio if I hadn't seen the suggestion here.

I went down to the boat yesterday and tried pulling on the radio and it wouldn't budge at first. Then I tried pulling on the adjacent stereo, and it came right out. I figured that if they didn't go behind the bulkhead for the radio, they probably didn't for the VHF either. So I reached under the radio bezel and felt around (couldn't see down there, and camera could not focus that close), and it seemed like there was some caulk down there. So I went at it with a putty knife to break the seal and gently start prying. After some effort, the combination of black adhesive pad and clear silicone caulk released all around the radio and it came out. (see pics below) I haven't pulled it all the way out because I want to understand the wiring first. But it looks like this project will be a lot easier than had I feared. I may have some additional questions about completing the install (RAM mic compatibility between different generations of radio, etc.) but I will start a new thread if/when I've exhausted other sources of info first.

In your photo, you have a piece of teak trim on the right side of the white panel. I can see a screw at the base of this trim. Have you tried removing the trim left and right to see if the panel just slides out?  (pull it toward you using the front of the VHF/stereo). This is what the wood panel does on the 2003 model.  If this was not removable as built by the factory in 2001, maybe the installer made it so?...

That is what I originally hoped to do, but close inspection showed that the fiberglass bulkhead there is part of one very large molded piece including the adjacent closet to aft, which extends all the way down to the floor under the nav station and also wraps around to the front of the closet. So if yours is removable, it was either a design change or a cut in the fiberglass was made by the installer.

Good points. If he's using a paddlewheel for STW, then growth on the paddlewheel could have an even greater effect on the observed speed than growth on the hull and prop.

As stated before, I don't know what prop specs apply for his particular engine/boat combination. But if a 15x10 is recommended, I still wonder why he had 15x9 before, and what issues caused him to increase pitch. Those issues could say more about the true root cause. Obviously, prop pitch is usually adjusted because of too high/low engine RPMs at full throttle, and miscalibrated tach could lead to an incorrect prop selection.

Are you using the same laser to measure your engine RPM? If not, and you're using your tachometer for the engine RPMs, the difference of 50 RPM is easily within the calibration error of the tach.

What does your manual say about gear reduction ratio of your transmission? (Please report back on that, since it it impossible to diagnose anything without this information.) 2:1 sounds reasonable based on what I posted before. It also explains why it will be VERY hard to turn over your motor using your prop. Do you have a compression release valve on your motor? Because I see NO WAY that you can use the prop to turn over your engine without releasing compression first. In fact, IMO not being able to turn your prop is a good sign that the transmission is not slipping.

Why did you raise the pitch of your prop? It sounds to me like that may be causing your problem. Even without the transmission slipping, an incorrectly pitched prop can cause other problems like water turbulence that could cause the prop blades to slip in the water, even without your transmission slipping. Just like wind separating from a poorly shaped sail, similar things happen to cause loss of laminar flow over the blades of an improperly pitched prop.

I'm not an expert at this at all, but it sounds like you need to provide more detail to get help here.

Been having trouble with my boat slowing down, I have put the transmission in forward or reverse on the hard and cannot move the prop,, my shaft rpm is a little less than half than the engine, i.e, engine rpm 2000 shaft rpm 950, (hand held laser)...

I am not sure I understand what you're saying here. (How can you have 950 shaft RPM if you can't move the prop?).

But do note that the transmission has a gear reduction. 2.1:1 sounds reasonable, but you need to check the specs for your model of transmission. It should be in your Universal manual. FWIW, my manual says:

HBW 50lZF 5M (2.05 : 1)
HBW 100lZF 10M (1.79: 1)
HBW 150VIZF 15MIV (2.13: 1)
HBW 150NZF 15MA (1.88: 1)

I'm no expert at this, but I've never put the motor in gear while on the hard because I assumed that the cutlass bearing would get burned up without the lubrication and cooling provided by water immersion. Could this be why you can't turn it any more?

I'm sure there are others here who know much more about this than I do.

Download the instructions and see how it's likely mounted?  Maybe there's a trick to the bracket, like a stereo bracket/faceplate?

There is no trick to the bracket. The included flush mount brackets, if they are used, screw in from the sides to prevent the radio from coming out. There is no faceplate, because the radio's face is larger than the body, so it's basically a built-in faceplate.

I'll have to re-check, but my locker aft of nav station is cedar lined, and I thought the forward cedar panel blocked access to that back area. So I would likely have to remove the cedar lining. Even if I can get to it, there's a stereo mounted right next to the VHF which prevents access to the aft side of the radio's bracket, so I'd have to remove the stereo to get to the VHF bracket, and that still does not solve the problem of how to get to the forward side of the radio. It gets messy real fast. My best hope is that the original installer bypassed this mess by just pressing the radio into the hole and maybe adhering it with caulk. Otherwise, it becomes a real hassle to rip out something that's basically working OK.

I just realized that this radio does have DSC, so I'll have to go check whether it's interfaced with GPS/chartplotter and whether the MMSI has been programmed. The radio allows changing the MMSI once, so I'll also have to figure out whether that's an option or I need to contact on of the previous owners to ask them to transfer their MMSI to me (if they even know how to do that).

T4 is regular multi-grade Dino oil. Not synthetic. Synthetics are T5 and T6.

Good idea. I know that Standard Horizon sells flush mount brackets that are screwed in from behind, but maybe they didn't use them. I'll try gently prying it out.