What is the best sealant for sealing motor mount holes?

[Bubbasboat]

I usually use pure silicone for most water tight sealing requirements. What is the best sealant for sealing motor mount holes during motor replacement? After all, we're not sealing the kitchen sink!

 

[GA_Boater]

Re: What is the best sealant for sealing motor mount holes?

3M 5200 or 4200. Save silicone for the kitchen sink because sinks don't. Sink that is.

 

[Scott Danforth]

Re: What is the best sealant for sealing motor mount holes?

3M 4200. i recommend the fast cure

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

I like that, "Sinks Don't"!! Really, I figured regular silicone would not be appropriate. Never replaced a motor myself, so knew I should ask! I looked into specs of 3M 5200, I see where it works on motor mounts on fiberglass transoms in applications, it does indicate a compatibility with metal substrates. I have an aircraft aluminum reinforced transom, see the photo. Will 3M 5200 work in this application? Thanks.

3M 5200 or 4200. Save silicone for the kitchen sink because sinks don't. Sink that is.

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

I see the 4200 dries totally in 24 hrs as opposed to the 5200 which can take up to 6 days. I also see that 4200 is half the strength of 5200 which allows for eventual dis-assembly of parts. I hope this is the last motor I put on this hull. Why choose the fast dry 4200, presuming you have the time to allow the 5200 to completely cure?

3M 4200. i recommend the fast cure

 

[JustJason]

Re: What is the best sealant for sealing motor mount holes?

Any type of polysulfide sealer. I've been using Life-Calk for years.

 

[BigBaitBigFish]

Re: What is the best sealant for sealing motor mount holes?

5200 can take more than 6 days...I had it curing for 10 days and it was still 'tacky' to the touch, but didn't come off on my hands by then. Took 5-7 days before it would not come off on my fingers to the touch.

This was at 60deg F in my garage, if you are using in warmer conditions it could cure faster.

 

[82rude]

Re: What is the best sealant for sealing motor mount holes?

5200 is good ive also used marine goop with great success.

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

Were the end results worth waiting over 10 days to still be tacky?

How long before it totally cured?

Is this normal dry time for a product like this, seems very long!

5200 can take more than 6 days...I had it curing for 10 days and it was still 'tacky' to the touch, but didn't come off on my hands by then. Took 5-7 days before it would not come off on my fingers to the touch.

This was at 60deg F in my garage, if you are using in warmer conditions it could cure faster.

 

[oldandintheway]

Re: What is the best sealant for sealing motor mount holes?

I usually use pure silicone for most water tight sealing requirements. What is the best sealant for sealing motor mount holes during motor replacement? After all, we're not sealing the kitchen sink!

Are we talking about plugging the old holes from a different mounting pattern ?
If so, I have successfully used MarineTex without any issues.

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

No, my new motor mount fits existing holes in transom. I am looking for the proper sealant for sealing the mounting bolts and holes.
I did get some 3M 5200 today, figure with the remaining prep before first water I will have time for proper drying of the 5200. Would still like to know more about the quick dry 3M 4200 version!

Are we talking about plugging the old holes from a different mounting pattern ?
If so, I have successfully used MarineTex without any issues.

 

[Scott Danforth]

Re: What is the best sealant for sealing motor mount holes?

since the holes are above water, you do not need 5200 which is intended for below the water line.

the fast cure 5200 cures in 24 hours as well

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

Two of my mount holes are above water and two are below water line. Sounds like I should stick with the 5200. What about this 5200 quick dry, all I've seen is the quick dry 4200.

since the holes are above water, you do not need 5200 which is intended for below the water line.

the fast cure 5200 cures in 24 hours as well

 

[Georgesalmon]

Re: What is the best sealant for sealing motor mount holes?

You don't have to wait for the 5200 to fully cure to use your boat. It will cure just fine even under water. Its a moisture cure product after all. It won't wash off unless its in a place with a very hard spray of water hits it. Motor mounting holes don't have that problem. There is a fast cure 5200 but its hard to find unless you look online and I think it only comes in caulking tubes and you don't need very much.

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

Excellent point. My problem is, your being from WI can surely relate too, temp today is within the operating temp of the 5200, but my nighttime temps fall below freezing this time of year. I will hit 19 deg tonight with highs in the 30's and 40's for the next few days. Today it will be 72.

My question is; How sensitive is 5200, or 4200 for that matter to freezing during cure process?

You don't have to wait for the 5200 to fully cure to use your boat. It will cure just fine even under water. Its a moisture cure product after all. It won't wash off unless its in a place with a very hard spray of water hits it. Motor mounting holes don't have that problem. There is a fast cure 5200 but its hard to find unless you look online and I think it only comes in caulking tubes and you don't need very much.

 

[Scott Danforth]

Re: What is the best sealant for sealing motor mount holes?

freezing temps simply slow the curing process.

 

[Bubbasboat]

Re: What is the best sealant for sealing motor mount holes?

Great, 3M 5200 it is! Water, temps including freezing are of no concern, I can use the boat immediately, as long I don't hit it with high pressure water spray and best of all, I have a brand new tube sitting right here. Thanks to everyone's great info, I'm one step closer to being on the water! Thank you

freezing temps simply slow the curing process.