1993 Hunter 42 Passage CC: Leaking near a few of the keel bolts. Ulcer time.

Ralph Johnstone · Sep 25, 2023

dlochner said:
Leaking might be a good sign, since it means the water is being fresher and is not stagnating and becoming oxygen deprived.

Makes one wonder what keel bolts are made from. 302 and 304 I know are subject to crevice corrosion. 316 fares a little better. Makes you wonder why manufacturers don't use something with higher crevice resistance, like a prop shaft in a gland which never crevice corrodes no matter how long it sits.

Just don't look pretty enough, I s'pose.

Ralph Johnstone · Sep 25, 2023

BabuBoat said:
I that 316?

Again please ?

dlochner · Sep 25, 2023

BabuBoat said:
Sorry. The prop shaft illustrated. Do you know the steel type used?

A lot of shafts are made of Aquamet. It is SS, however, allegedly is it a alloy specifically designed for prop shafts.

https://www.aquamet.com/services

Ralph Johnstone · Sep 25, 2023

BabuBoat said:
Sorry. The prop shaft illustrated. Do you know the steel type used?

That's a pic of my shaft after many years in service with 5 months every winter without turning a degree. Given that it was made in 1998 or earlier, it's likely Aquamet. There are more exotic alloys out today that have higher strength that Aquamet but I don't see how they could have more corrosion resistance.

Aquamet starts out its life as red hot billets (slabs) of metal and is then drawn out into rods of varying diameter. From this rod, keel bolts could have been made just for situations like yours where water is trapped around the bolts due to a leak in the keel/stub joint. The joint could be sealed from the outside (water and all) and forgotten. No need to drop the keel. I'd be more than willing to pay another $100.00 on a new boat just to have Aquamet keep bolts.

Leaky keel

? Bah humbug

! Something that "almost never happens". But oh god, if it does happen, you'll wish you could have spent $1,000.00 extra for Aquamet keel bolts. Cheap insurance.

jssailem · Sep 25, 2023

I have not heard of “Aquamet” being used for the purpose “keel bolts”. It may be possible. If there is practicality of its use I would give this site a call. They are likely to know.

https://www.marinemachining.com/other-products-n-services

While I have a new shaft made from Aquamet, my suspicion there would not be significant improvement results using the material as a keel bolt. The issue is not the bolt breaking it is the the fiberglass structure breaking down. In a hard grounding the bolts trying to resist the unnatural forces fracture the fiberglass around the keel stub and hull. Even microscopic fractures give water a path into the boat. The only way to address such issues is to rebuild the structure. I suspect, for most owners, this is beyond their pocket book tolerance. So, they tolerate a little water in the bilge, slap adhesive caulking on the inside (after all, out of sight out of mind), or haul the boat and attempt to repair the outside. For some this resolves the issue at least til they sell the boat.

Ralph Johnstone · Sep 25, 2023

jssailem said:
Even microscopic fractures give water a path into the boat.

My only concern is encapsulating the bolts in a wet environment when the exterior is sealed. With a cheaper SS this would pose a problem. Perhaps with a higher quality SS, a simple exterior sealing job may be acceptable, all the while hoping there is no structural damage internally.

jssailem · Sep 26, 2023

BabuBoat said:
the human analog might be,, living with an aneurysm

I am not so sure.. Maybe a flesh eating bacterium.
There are treatments and there are solutions.. Sometimes the solution feels out of reach depending on where you are and what you have.

You are looking at the symptoms. Water in the bilge. You have experienced some events. Inspection and clarification of the extent of any damage from the event would be the first step to a solution. Working on the inside is like putting a bandaid on an infectious sore. Sealing the outside and then drying out the inside would be addressing the symptoms. Removing the keel and resolving any damage would be the steps toward a resolution and possible cure. At least that would be my medical unprofessional opinion.

I agree Ralph…

The Aquamet, as identified on the site, is still a SS alloy. SS is always subject to corrosion when in an oxygen depleted environment. 316 is better than 304. As I suggested contact with the website may be able to share clarifying data as they are a specialist machine shop using Aquamet.
It seems to me there are practical limits to the sourcing of materials. 316 is a good compromise. If water has intruded beneath the hull stub shield, then the water is in a place that is without oxygen supply. SS even 316 or aquamet will act based on its exposure.

I had to replace my prop shaft when I discovered pit corrosion even though the area under the traditional stuffing box looked shiny and smooth.

This is what I found after opening the stuffing box and then sliding the shaft up the shaft log. Evil hiding out of sight.

Your shaft looks to be surviving the exposure to the elements.

Terry Cox · Oct 12, 2023

The only keel bolts that I'm aware are those located in the main bilge beneath the center settee, one located beneath the compression post and two located beneath the shower sump box. I've not measured them, but ours all seem to be of the same size.

Terry Cox · Oct 13, 2023

BabuBoat said:
Maybe later than 1993 builds...

Ours was built in 1991. I'll check the studs the next time to the boat to confirm their sizes.

Terry Cox · Oct 13, 2023

BabuBoat said:
My friends on S/V Jibsea tell me there is a 1/2" bolt just beneath the companionway steps.

Our boat has two there, under the shower sump box.

Terry Cox · Oct 14, 2023

BabuBoat said:
That makes 8 bolts, and they are all 1".

Just checked ours. Two beneath the shower sump box, four in the main bilge beneath the center settee and one beneath the compression post. All are one inch.