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Author Topic:   Montauk - water tight self-tapping screws?
bigjohn1 posted 12-05-2004 07:43 AM ET (US)   Profile for bigjohn1   Send Email to bigjohn1  
2005 170 Montauk (six weeks old)

Last week, I noticed that 4 of the 8 self-tapping screws which secure the fuel tank hold-down brackets on my 170 were loose. By loose, I mean they had backed themselves out about 1/3 of the way. Rather than simply tightening them all back down, I took one completely out to have a close look at the sealant used. It looked like only the first 2-3 threads had any traces of sealant on them. I decided to take all 8 screws out and coat them well with 5200 fast cure and then re-installed all of them without incident.

Along with this, I have seen the hardly noticable but very early signs of a rust stain coming out of one of the swim ladder securing screws at the back of the transom. These two separate incidents have me a bit concerned on the sealing and installation procedures Whaler uses when they assemble these 170's. I boat in fairly harsh tropical saltwater conditions but do a very thorough job of rinsing everything down after each use. Once the boat dries, I store it covered in a carport.

QUESTION: Should I take out the screws which secure the swim ladder and investigate the source of rust? I'm quite sure its one of the screws beginning to rust - what else could it be? Perhaps an adequate amount of sealant was not used when the screws were originally installed? To take this a step farther, should I be checking the screws which secure the cleats to the boat as well? I have also noticed the early signs of rust coming out from in between the bottom mounting surface of the bow light where it meets the gel coat surface up forward. If I take it back to the dealer, what other than resealing all these various screws can they realistically do? I'm not a woodworker at all but I have always assumed that once you remove a self-tapping screw from wood then re-install, it will never be as tight or strong as before.
Big John

divefan posted 12-05-2004 08:56 AM ET (US)     Profile for divefan  Send Email to divefan     

I had rust coming out from under the rubrail in the back of the boat near the logo. The dealer told me that sometimes the screws underneath rust. Why that would happen is beyond me. Supposedly he fixed it when I had the boat in for service. He may have because I haven't had it come back yet in the same spot.

If you are worried about backing out screws and then not holding when you put them back you can always go to a slightly bigger screw next round along with the 5200 (I'm sure you already thought of that yourself). I don't see what other choice you have. Other than letting the dealer have at it and let him be responsible for the outcome in case it doesn't hold.

Good luck with your new toy. :-)

AQUANUT posted 12-05-2004 11:40 AM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
hey john,
ltns, stainless steel will rust in an extremely salty environment. all you can do is purchase the highest quality available. I use 316. you ight know this already, but the best finish on metal as far as a shiney surface chromeplated stainless in the bimini tops used on the Montauk170.

frankly, I enjoy the finish on brass...but it is far from low maintenance...unless you like the color green.

p.s. hows the fishing?
been doing the steelhead here on the rogue river [oregon]
and strippers down on the colorado a few weeks back


jimh posted 12-05-2004 03:11 PM ET (US)     Profile for jimh  Send Email to jimh     
Terry--What does "ltns," mean at the beginning of your reply?
AQUANUT posted 12-05-2004 06:28 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
sorry Jim,
ltns< means long time no see, common internet lingo for some..perhaps not so commonn for others...{I haven't seen Joe since he was at my dearlership this summer}


Jerry Townsend posted 12-05-2004 07:00 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
John - as you are aware - all stainless steels are not corrosion resistant. The best one for corrosion protection is the 18-8 series, which may cost a bit more than other alloys because of the different alloying and the heat treatment.

The only detriment is that an 18-8 screw will not be bright and shiny as an self protecting oxide coating will develop. If the bright and shiny screw is important, they can be chrome plated.

I would guess that 18-8 stainless screws would have to be ordered from some industrial supply outlet.

Aside from the material aspect, your using 5200 would help regarding the screws loosening up.

The observed rust on your swim ladder mount is clear evidence of water being in contact with the screws. That can only happen if those screws were not properly sealed. Consider replacing and properly sealing those screws.

I am not a metallurgist and others may have additional information. ------ Jerry/Idaho

bigjohn1 posted 12-06-2004 12:12 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Thanks guys, I do appreciate the feedback. I guess I am of the meticulous sort who would rather do the re-seal of the screws myself. Since its my boat, I think I'd be a bit more careful on doing a thorough job as opposed to the
$6-per-hour mechanic's helper they'll likely give this job to so the mechanics can tackle real mechanic work.

I think there is a dawback though and simply doing it myself and not at least complaining to the dealer will have its pitfalls as well. We are a bit removed from mainstream USA way out here and if I need any new screws due to rust, I can already hear the dealer telling me it'll be 3-4 weeks waiting on parts from Whaler. I can get nearly anything online shipped out here in 7-10 days but the dealer takes weeks longer - go figure.

BTW AQUANUT and Divefan, diving some off-shore FAD's last weekend for Mahi and Wahoo, I had a Pacific Black Marlin swim right up to within 10' of me. Popped him in the back of the head with my Rob Allen 120cm speargun and it barely phased him...looks like its time to get the tuna rig out!
Big John

divefan posted 12-06-2004 12:44 AM ET (US)     Profile for divefan  Send Email to divefan     

Man I wish I could have been there to see the black. RA's take down some big fish all over the world but somehow I think the 120 might be a bit small. :-) I'd say you need a 3/8" shaft with a breakaway tip and a lot more bands than the 120 has to get the attention of something that big for sure. What a thrill to see that so close in the water. It must be paradise where you are. PICTURES! PLEASE.

Tom W Clark posted 12-06-2004 12:06 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

The rust you are seeing is probably from the swim ladder itself, not the screws, but you should be able to make that distinction fairly easily by disassembling it.

Rusting hardware is a separate issue from sealing of the screws. The grade of stainless steel used will have much to do with how well it holds up.

In general, stainless steel Type 304 (aka 18-8) is the most common and readily available. Type 316 is superior to this and more expensive and hard to buy at the retail level.

I was under the impression that Boston Whaler now brags about using fancy chrome plated stainless steel fasteners. This is why I would suspect a boarding ladder made by a third party rather than the screws that secure the ladder. Or perhaps the screws were supplied by the ladder vendor and are not of the same quality?

As for sealing, I do not know what Whaler's practice is now. Historically, they applied absolutely no sealant to small screws around the boat.

I absolutely think it is a good idea to remove these screws and apply a polyurethane or polysulfide caulk like 3M 5200 (4200) to the threads of these fasteners, especially those on the floor of the boat or near the waterline.

erik selis posted 12-07-2004 05:41 AM ET (US)     Profile for erik selis  Send Email to erik selis     
Corrosion resistance of stainless steel is not only dependent of the amount of Cr(chromium)and Ni(nickel)but also the amount of Mo(molybdenum) in the alloy. The reason that 316(18-10)is much better corrosion resistant (to salt water) than 304(18-8)is because it contains Mo. The 304 alloy does not.

Also, it's actually not the Ni that enhances the corrosion resistance to salt water but rather the Cr. You can use a lower grade stainless steel (304) and have it chrome plated afterwards. Yes, you can chrome-plate stainless steel.

Another thing you can do with lower grade stainless is having it chemically polished. In this process the Cr and Ni in the alloy fill the microscopic pours at the surface while the Fe (iron) molecules rest more concentrated in the middle of the mass. The surface is very shiny and hard. Be sure not to drill any holes after this process because corrosion will be enhanced. If you have it mechanically polished before it is chemically polished the results are amazing.

Here's some interesting reading on stainless steels used in salt water environment.

For all you need to know about stailless steel:


erik selis posted 12-07-2004 05:54 AM ET (US)     Profile for erik selis  Send Email to erik selis     
Fixed link:

bigjohn1 posted 12-09-2004 12:07 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Tom, thanks for the tip on the swim ladder, I had not thought of that and will give it a very close look.

Eric, thanks for the very thorough indoc on ss types, great info that I'll use for future reference when deciding on what types of screws and parts to try and find.
Big John

bsmotril posted 12-09-2004 04:06 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
On my vinatage 1998 whaler, the stainless screws are also Chrome plated. Where the plating get's damaged or cracked, the screw will begin to corrode under the plating. This has only happened twice, both on screws in the cockpit deck which get rubbed by coolers with sandy bottoms, feet, Sharks, etc. I don't know if the later models still use the plated fasteners. If they do, check the plating integrity as a possible source of the rust. If the brackets on the ladder where they attach are also plated, that might have been abraded when the ladder was installed also. BillS

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