Marine Sealant

Corrosion, Paint, Through Hulls, etc.
Posts: 17
Joined: Sun Mar 01, 2015 7:54 pm

Marine Sealant

Postby tjc7t7 » Wed Apr 25, 2018 5:43 am

I am getting ready to install a new depth finder on the boat that uses a thru the hull transducer and was looking for some suggestions on the best
sealant to use with our aluminum hulls. I would love to know what was used on the old one. I had a terrible time getting it out of the hole that thing was really stuck in there. Thanks in advance!
1984 28 Express hardtop single 318. Lake Erie Jefferson Ohio

Site Admin
Posts: 1336
Joined: Sat Jul 12, 2014 5:06 am
Location: Rock Halll, MD

Re: Marine Sealant

Postby Fastjeff » Wed Apr 25, 2018 6:05 am

3M makes a sealant (I think it's called 5400) that doesn't death grip like 5200.

"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington

Site Admin
Posts: 758
Joined: Fri Jul 11, 2014 9:15 pm

Re: Marine Sealant

Postby jralbert » Wed Apr 25, 2018 11:38 am

Jeff is correct, 5200 has a really strong grip - it's referred to as a "permanent" adhesive, hardening like rock or steel. It's 4200 that you want to use - it seals well and is considered removable. Here's how it's described by the mfr:

"...3M 4200 Fast Cure is a one-part general purpose polyurethane sealant with good adhesion to wood, fiberglass, gelcoat, plastic, and metal. When cured, 4200 forms watertight, weather-resistant seals on joints and boat hardware above or below the waterline.

4200 FC (fast cure) is ideal for hardware and bedding applications. It is paintable and sandable. While 3M 5200 sealant results in permanent bonds, 4200 has approximately half the strength, making it a good choice for applications where the bond may need to be broken in the future such as replacing hardware..."
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

Tin star
Posts: 38
Joined: Sun Jul 02, 2017 8:09 pm
Location: Curtice Ohio, Lake Erie

Re: Marine Sealant

Postby coastie1160870 » Sat May 12, 2018 10:59 am

I am mounting a new transome mount transducer to my 32 Express, this year.. I contacted the makers of "FLEX GLUE" because they clim it good on metal.. They said it could be used to mount the plastic transducer to the aluminum hull, with no problem.. But I;m looking for a 99% permanant application, as I don't intend to remove this transducer... I'll let you know in a year or two if holds up..!
R.A. Campbell
32 Sedan-Bridge
260 Chrysler Twins