centerboard pivot bolt replacement

[Paul T Davies]

I have a 72 19' O'day. Water is leaking from the seal on one side of the pivot bolt. I have purhchased a new bolt, washers and rubber seal. Looks pretty straight forward once I am able to keep my center board stationary. Curious to know if anyone has done and if you put some type of grease on the bolt or liquid sealant around the rubber washers. Also, to make sure I do not overtighten my assumption is one should just tighten until you can see the rubber seal is beginning to compress.

Any help would be appreciated.

Thanks

Pdavies

 

[Sunbird22358]

I looked up a description of the Mariner centerboard from someone who had refinished theirs. The centerboard actually pivots on a Bronze bushing apparently (My DS II uses a nylon/plastic bushing) that (assuming the same setup as the DS II) will be slightly longer than the CB is thick, this will prevent you from pinching the CB if you tighten the bolt too much. So, I'd suggest that you insert the bolt through the hole in the CB trunk, apply a thin bead of sealant (marine silicone works well) between the rubber washer and the bolt head, apply a thin layer of sealant between the rubber washer and the CB trunk (the sealant will make up for any iregularity in the CB trunk side). Repeat for other side. When you tighten the bolt, don't snug it up tight right away, just bring it up to the point where the sealant just starts to squeeze out, then after a few hours, you can tighten it the rest of the way. This is the proper procedure for any time that you use sealant, and it intended to ensure that a thin layer of sealant will remain when the fitting is tightened down. I'd say, if in doubt, leave the bolt less than absolutely tight, you can always tighten the bolt more after launching if needed.

 

[mjp83]

Sunbird,

I too have a small leak on my mariner cb bolt. I have used silicone on the bolt as you described, but the bolt will rotate slightly as I lower the cb, breaking the silicone seal around the threaded side of the bolt, where the nut sits.

The bolt is galvanized and I am questioning it's originality. I did see the same one on Stuart marines website.
My boat came with new bottom paint where they also recoated the cb. I see a bushing from under the boat, sticking out of the cb equally on both sides.

My question, what is supposed to be fixed, and on what does the cb actually rotate? The bolt, the bushing or does the centerboard have another bushing in it ( I saw this on the boat Orien). I hope to just take the bolt out, clean the cb bushing with some fine sandpaper, place marine bearing grease in the bushing and slide the galvanized bolt back in, sealed as before, but now hopefully remaining still.

Thanks!

 

[Sunbird22358]

The CB pivots on the bronze bushing and the bolt needs to be tightened enough to clamp the bushing into the CB trunk. I'd DEFINITELY replace that galvanized bolt with a stainless-steel one like would have been there originally, especially if you sail in saltwater.
It sounds like your bolt is too loose and so the bushing is rotating and causing the bolt to rotate as well (bolt may be rusting enough to be gripping the busing. A little waterproof grease between the CB and the bushing should also help (my CB is fiberglass so I coated the inside of the hole in the CB with a thin coat of epoxy mixed with graphite powder, later added a VERY thin coating of waterproof grease (OMC "Tripple-Guard Grease", now available as Bombardier Brand from Evinrude Dealers) to the bushing.

 

[mjp83]

Aha!

Thank you, it appears the boat yard coated the bushing with anti fouling paint, and it has now seized itself to the cb. I will try to remove the cb and free the bushing. I also just came back from hardware store with longer bolt so that no thread remains inside cb trunk. I have washers to tighten it up past the exposed threads.

 

[mjp83]

So I did some more work on her, and also called Rudy from D&R marine.
The fix? White lithium grease!
First off I purchased a new 5/8 bolt with a solid bolt section of 2.5 inches to go through cb trunk. Then two new rubber washers, which were to fit a half inch bolt, which will really hug the 5/8 inch bolt. I then supported the cb from underneath while boat was on trailer, and pulled old bolt out. Cleaned inside the bushing with 220 sandpaper, greased it up well, and per Rudy's instructions, placed the white lithium grease between cb trunk and new rubber washer. Tightened it down to snug, and no more rotating bolt and no leaks!