Mainship 390 Rainwater in Bilge; repost

[Byekurman]

Someone has to have had this issue! Please advise

2003, Mainship 390, single engine
I'm having an issue with rain water entering my bilge. It is running down the port channel along hull,, under main deck,, and into my engine room where the water is guided into my middle bilge. It's triggering my middle bilge pump. I'm pretty concerned with all this rain were having in Richmond VA area. After reviewing drawings in the Mainship manual, it appears the port stern deck drain and the bridge port stern deck drain/support post are joined together, maybe in the lower section of the gunwale, near the rear area of the port water tank (possibly accessible through the most rear stern lazarett). Has anyone had this problem? Has anyone had to access this area where the drains come together and required repair? If yes, can you explain how you gained access to this area?

 

[USNA74GRAYGOAT]

Hi Dave. I noticed you are in the Richmond area and keep your MS 390 in Urbanna. I have a MS Pilot 30-2, the Galene, at URBBY / Urbanna Boatyard & Marina. Any chance we are neighbouring slip holders there? FYI yours is not the only MS in Urbanna with water leaking into the bilge, but fortunately I’m pretty certain I know what needs to be addressed to stop this.

Cheers and I hope get some good advice from another 390 owner on how to find and stop your leak source.

Rob
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[Byekurman]

Hey Rob. I'm at Urbanna Creek Yacht Club, across the creek. I'm in slip 57. I'll be on the boat tomorrow. I'd appreciate any advice on this water intrusion.

 

[Bacchus]

Not familiar with the MS 390.
Many MS s ( as well as other makes) leave leaks at the hull/deck joint under the rubrail.

 

[Byekurman]

I'll check out with a hose tomorrow. Thanks Baccus

 

[USNA74GRAYGOAT]

Dave,

Don is right on about MS leaks. I’ve identified the hull/deck joint under rubrail, and detioration and shrinking of the windshield gaskets which are no longer available. I get infiltration in the engine room P/S bilges from the hull/deck joints.

Pretty certain the deepest bilge fwd of the berth band underneath the floor of the heater and AC unit comes from the 3 leaking window gaskets.

The biggest PITA is the manner that MS built these Pilot boats with no easy interior access to hull/deck joints and any bilges other than the engine room.

I’ll be back from vacation next week and will check in with you so we can meet at your boat sometime. We nearly purchased a 390 before deciding to go for the Pilot.

Good hunting!

I use a 2-gal wet/dry vac to remove any water I find after frog choker rains like you had last evening in Urbanna. I don’t get any water infiltration while underway in good weather.

You have much greater potential for leaks in your trawler than I do. Where exactly are you finding it? Have you tried using fo

 

[Byekurman]

I have located the source. There is a collection box at the rear inside port hull area that releases water into the rear most port scupper. There are three, 1 11/2-2 inch, hoses that connect to this box that can seen through the lazarette. The hose that comes from my rear most bridge port drain is leaking badly thus placing water into my bilge

 

[Bacchus]

Dave,

Don is right on about MS leaks. I’ve identified the hull/deck joint under rubrail, and detioration and shrinking of the windshield gaskets which are no longer available. I get infiltration in the engine room P/S bilges from the hull/deck joints.


The biggest PITA is the manner that MS built these Pilot boats with no easy interior access to hull/deck joints and any bilges other than the engine room.

Rob

Repair of the hull / deck joint does not need inside access.
I have posted a description, pics and links on my Bacchus website for those interested. I certainly agree that MS did a mediocre job of attaching the hull to deck but honestly it is not uncommon for many manufacturers of production boats.
There is a fairly easy temporary fix involving simple caulking the rubrail.
I favor a more involved / more permanent fix requiring removal of most if not all of the rubrail and dealing with gaps and conne tor deficiencies before replacing & sealing the rubrail.

I don't know if MS used the same / similar windows on the Pilots as the Trawlers but mine are AL2000 a Div of Pompanette and I believe gaskets are available from them... worth checking
https://pompanette.com/product-category/replacement-parts/gaskets/windshield-gaskets/

 

[USNA74GRAYGOAT]

Hi Don,
Thanks for your comments - I will check your website for more details for removing the rubrail and caulking. I’ve discussed this at length with Rich Gano who did same on his Pilot 30, the Frolic. I assume you know Rich as a frequent contributor on TF. My complaint about no access to the hull to deck joint from inside is that it prevents you from visual checks of leak finding with food dyes, washable color markers etc on the exterior and seeing where leaks are by seeing the colored water on the inside hull. Like I could always do on any of my 7 sailboats. Easy peasy find.

Love your 34HT trawler. MS hit a HR with that design for those of us who like the additional space and comforts a trawler delivers but do not want to drive or socialize on a fly bridge.

Calm seas,
Rob

 

[Comodave]

I have virtually no access to the hull to deck joint on my Formula. Not that I expected any.

 

[Bacchus]

Hi Don,
Thanks for your comments - I will check your website for more details for removing the rubrail and caulking. I’ve discussed this at length with Rich Gano who did same on his Pilot 30, the Frolic. I assume you know Rich as a frequent contributor on TF. My complaint about no access to the hull to deck joint from inside is that it prevents you from visual checks of leak finding with food dyes, washable color markers etc on the exterior and seeing where leaks are by seeing the colored water on the inside hull. Like I could always do on any of my 7 sailboats. Easy peasy find.

Love your 34HT trawler. MS hit a HR with that design for those of us who like the additional space and comforts a trawler delivers but do not want to drive or socialize on a fly bridge.

Calm seas,
Rob

Rob
OK understand the desire for access. I can't get to or view the joint from inside but I can see the interior hull below so tracking down source was doable.
I dont know what your access is at the stern, but that was an area where I also had some leaks and lead me to start pulling off the rubrail. Steve Cyr's Stella Blue site and his knowledge was very helpful to me when getting to know my MS. His was a 400 but had lots in common with the 34.

Don't know if it helps, but I've had some success using metallic foil tape when trying to find / eliminate leaks. By taking suspect areas and flooding with a hose it provided some clues whether the leak had decreased or stopped.

Others have gone the route of cleaning & recalling the top of the plastic of the rubrail where it meets the deck. IMO it's not as permanent but it is much easier to do. It could be used as a temporary fix and a way to confirm where the leak is originating from.

Rich & I have swapped messages frequently and he is a very good source.
Thanks for the MS 34HT comments and I agree... its amazing there are so few in existence. For us it's a perfect balance but I realize the hardtop is not for everyone.

Good luck with the investigation

 

[Shrew]

I have located the source. There is a collection box at the rear inside port hull area that releases water into the rear most port scupper. There are three, 1 11/2-2 inch, hoses that connect to this box that can seen through the lazarette. The hose that comes from my rear most bridge port drain is leaking badly thus placing water into my bilge

The A/C drain pans run the drain hoses into the bilge. The main Salon AC is under the stairs. Are you sure you're no looking at the AC drain hose?

Same to the OP. Have you excluded the AC condensation drains as you're culprit?

 

[tiz]

I have located the source. There is a collection box at the rear inside port hull area that releases water into the rear most port scupper. There are three, 1 11/2-2 inch, hoses that connect to this box that can seen through the lazarette. The hose that comes from my rear most bridge port drain is leaking badly thus placing water into my bilge

Good find. Now, do you (or anyone) have a plan to access that area? Definitely interested in your solution. Good luck!


—Kevin

 

[Rpoconnor]

I have a 2004 Mainship 390 trawler. Several years ago I had a freshwater (rain) leak into the bilge. The water ran down the inside of the hull portside midship somewhere behind the fuel tank, so it was not possible to identify the source of the leak. I had read that the hull, deck rub rail area caused such leaks. I scrapped out all the existing caulk all the way around the rub rail on the entire boat and replaced with clear silicone caulk. This can all be done from the deck topside. No need to remove or unscrew the rub rail. You have to do this all around the whole boat. A leak can be anywhere along the rub rail, the water will flow to some low point and come in. I suspect the original caulking deteriorated, but you can never pin point where. No leaks now ... and it has been 5 years! Now, I have a leak somewhere topside leaving freshwater in the flybridge floor balsa core. Its small, between the rear legs of the table and the radar mast mounting plate. Have to find the source of the leak before I dig out the balsa core and replace.

 

[Comodave]

I don’t use silicone caulk on the boat. Once you use silicone nothing else will stick there so if the silicone is leaking you can’t get new caulk to stick there without sanding the area, and on gelcoat that isn’t what I want to do. I use Sika 297, I think, for general caulking. You can remove it and recaulk and the new caulk will stick.

 

[Rpoconnor]

I don’t use silicone caulk on the boat. Once you use silicone nothing else will stick there so if the silicone is leaking you can’t get new caulk to stick there without sanding the area, and on gelcoat that isn’t what I want to do. I use Sika 297, I think, for general caulking. You can remove it and recaulk and the new caulk will stick.

I should have mentioned in my post that it is essential to remove the old caulk entirely. Carefully scrap the old caulk out. I used a metal caulk removal tool (Amazon purchase) that I ground down on the sides to fit the area I was working on. Then sanded the gap, then cleaned the gap with Acetone rag. New caulk will not stick to old caulk and be waterproof. I will check out Silca caulk as oppossed to silicon caulk if it leaks again, but so far (5 yrs), so good. I do think that the caulk used needs to have flex to be effective in the rub rail area.

 

[Comodave]

The problem now is that regular caulks won’t stick where the silicone caulk was. It is extremely tough to get all the silicone off so something else will stick. That is why I don’t use silicone on the boat.

 

[BruceK]

Silicone caulks are not created equal. In my experience the "Bathroom" variety won`t take paint, the "Roof and Gutter" variety will, quite happily. Frightened by a tube of silicone during gestation is a hazard.

 

[Bacchus]

Im with Dave & others that deyest silicone as a caulk. It is not a great adhesive and eventually comes lose making the repair very difficult to get adhesion again. Lots of other choices. You can do the external seal much easier but when the hull flexez the chances of breKing that seL are higher.
IMO easy is temporary more difficult is more permanent. Always choices!

 

[keith c]

About two years ago I asked the MS brain trust the same question. I was having bilge water in several areas of the boat. Credit to Bacchus. I sealed the upper rub rail area. No leaks!!!

 

[USNA74GRAYGOAT]

Blue hull MS390 Bay Passing

Hey Rob. I'm at Urbanna Creek Yacht Club, across the creek. I'm in slip 57. I'll be on the boat tomorrow. I'd appreciate any advice on this water intrusion.

Dave,
I passed a MS trawler heading North on the Bay whike I was headed South to Mobjack on Monday 7/10. The NS skipper on the fly bridge started waving at me as though he knew my boat. Any chance that was you?
Rob
2003 MS Pilot 30-2 Galene