ThroughHulls

[Chris]

We are replacing our old Data marine electronics with RayMarine ST60. My Question is about sealant to use around through hulls.  The instructions say to use a sealant and make no suggestions as to which sealant. If anyone has any suggestions on sealant it would be appreciated. Ben Holland /ChriSea #832

[Mike Smith]

Chris (or is it Ben?) -

I always use 3M sealants - but there is some controversy about the 3M 5200 product. Some swear by it, but once you apply it, you will never, ever, get the fitting off (if necessary) without using a grinder. You might as well use West System epoxy! I recommend using one of their other, less permanent products.

Mike

[Chris]

FYI: Ben is the guy in the picture and Chris (who the boat is named after)is the admiral or my new wife.

[Gene Regan]

I have used 3m's 4200 with much success. It seals great and allows you to later remove the fitting from the hull with minimal effort. 5200 is better for things you do not wish to later remove. Hull to deck joints and the like. Good luck and Keep Smiling

[SteveLyle]

Generically:

- use a polysulfide caulk whenever you don't need/want a permanent seal.  Boatlife and 3M both make polysulfide caulks - I believe the 3M # is 4000.

- use a polyurethane when you want a permanent seal.  3M 5200 is a polyurethane.  You probably don't want it for what you're doing - if your senders had originally been calked with 5200, you'd need to blast them out.

Steve

[Mike Vaccaro]

A wise old boat smith told me that there's no substitute for 5200 and a properly backed bronze through hull.  When I asked about removing it, he said that properly installed and cared for, the boat would be scrapped before replacement was necessary; and if it WERE necessary, it can be removed with skill and cunning.  

Although our sensors are installed in this manner, there is always a risk since a typical piece of marine electronics has about a five year life span and manufacturers have a clever way of changing design and dimensions just enough to effectively obsolete the transducers!  The other down-side to a metal through hull is the potential for damage during a lightening strike if it's not properly grounded.

Since we don't have a bilge pump that can keep up with a 1 1/2" hole below the water line, there is no substitute for a properly installed through hull.  If it's below the waterline, don't hesitate to use 5200.  You can always fret replacement when the boat is safely on the hard!

Cheers,

Mike

[John Gardner]

My first boat had no thru hull and I installed a depth meter.

My present boat had two leaking through hulls when I bought it - not very surprising since the inside wooden wedge shaped washers were not wedge shaped and, more to the point, the holes in the hull were way over-size.  I took out both thru hulls, used epoxy to reduce the hole sizes, and re-installed them.  A season or so later the depth sensor failed and, like one of the earlier writers said, the replacement required a new design of thru hull.  I took out the obsolete one and put in the new.

I used 4200 every time.  No problems once installed.  Not too difficult to remove when necessary.