Engine Bracket Bolt Sealant

[Jason2tpa]

My OM and SM do not mention using a sealant on the 4 engine bolts securing bracket to transom, though I know it's necessary. Scanning online sources doesn't provide the definitive sealant to be used...some suggest 4200, 5200, or a non-permanent silicone gel.

I always lean towards the overkill side of sealing out water by using 5200. But for this particular use, I definitely do not want to risk pulling the gel coat off the transom if engine removal/repositioning is required in the future.

I've also read that some run a bead of sealant around the edges of the bracket after engine is locked in place. That seems overkill to me.

What are yall's thoughts, suggestions? Thanks.

[Sequoiha]

I always use a good marine grade silicone sealant. 5200 is a permanent adhesive, not necessarily the best sealant.

[rodbolt17]

NEVA EVA use silly cone.

at a minimum boat life caulk.

silicone has no shear strength and will leak soon.

about the best thing to do with silly cone for marine use is toss it off the bow.

[DennisG01]

Because 5200 is relatively permanent, I RARELY use it. Basically, only on things that I never anticipate removing and also things that don't see the sun since it's not UV stable. I've been using the BoatLife products for many years and they are pretty much my "go-to" stuff. For normal, everyday sealing I use LifeSeal as it's easier to use and less messy. For stronger and longer-lasting areas I use LifeCalk. That's what I'd use here - LifeCalk. But be forewarned - it's messy... you'll doing fine and then look down and wonder how it got THERE?!? Take your time with it. Excellent stuff, though. Great company, too - if you call them, you'll get an actual, live person who knows what they're talking about!

[boscoe99]

Another vote for silicone sealant. Marine type if one prefers.

4200 and 5200 are adhesive/sealants. There is no need for the stuff to adhere any two parts together. The attach hardware will do that.

If the bolt holes are properly sized for the fasteners there will be minimum clearance between the bolt and the hole. Properly mounted there will be no relative motion between the motor, the bolts and the holes. Shear strength of the sealant should not enter into the equation.All the sealant is doing is preventing water ingress into the boat. It does not take much.

Both Yamaha and other engine makers documentation say with respect to engine mounting to use a sealant. There is no mention of using an adhesive/sealant.

Bottom line however is to do whatever you want to do. There is no law that addresses this subject. Whatever floats your boat. Or keeps it from sinking and lets you sleep at night when the boat is in the water.

The good thing about the internet is that what ever answer one wants, to support a preconceived position, can be found on the inner web.

[walleye1]

I have used 100% silicone for the last 20 years and never had a problem.

[pstephens46]

Here we go....

[walleye1]

I have pulled engines from glass hulls with 4200/5200 sealer that would pull gel coat. Cheep 100% silicone clear from ace hardware. 2.50 a tube and it dries fast. 5200 can take 48 hours to dry and it runs all over.

[pstephens46]

Not a big fan of 5200 either. Seems like it shrinks some when it dries in addition to being a mess.

I have screws to secure fiberglass surfaces to other fiberglass surfaces. For example, the console is screwed into the deck. Bunch of screws and they always work themselves loose. I wonder what the best choice would be for a non-permanent Loctite type sealer to keep this from happening?

[rodbolt17]

let me tall bout a story of a man named Jed.
Actually it is a story of a marinia I worked at some years ago.
the motor was removed for steering cable replacement.
a year later we got an attorneys summons and a bill for almost 3000 bucks.

the silicone seal the tech used on reattaching the motor had failed.

claim was it caused the transom to rot.
the pics showed the seal had failed and water draing down the transom.

silly cone does not offer much lateral nor verticle shear strength.

no way are you going to bolt that bracket so tight to the transom it wont move some in use.

the marina paid and after that the policy was 5200.

now I don't like 5200 that much cause it touh to take the motor back off.

I removed a set of 200 Yamaha's from a 28' topaz many years ago.
actually lifted the stern of the boat off the rack and it would not let go.
lucky Tynes fiberglass was next door.

that is when I settled on 4200 or mostly boat life caulk.

[walleye1]

I have used J/B weld quick set on the screws. The
rite way is to fill the holes with resin and re drill or
go larger and use J/B weld to hold them.

[DennisG01]

The adhesion strength between 5200 and gelcoat is greater than between the gelcoat and fiberglass. Or, at least that's what a 3M rep told me years ago.

[walleye1]

I don't think you be able to get the screw tight.
Go bigger and put 5200 on the screws and tighten.
It's a given screws will back out on big water.

[rodbolt17]

that's why unless the marina or customer requests it, I wont use 5200.
to many times we had to halt a simple on/off for the glass man to fix the gelcoat wher I peeled it off to the glass.

never forget them swan point hulls.
they screwed and 5200 the cooler seat assy to the deck.
A few years after I started working with the guy that had purchased swan point the fuel line failures started.
getting the fiberglass seat base up was interesting.
same as the aft bait box in a 28 carolina classic .

[DennisG01]

I have screws to secure fiberglass surfaces to other fiberglass surfaces. For example, the console is screwed into the deck. Bunch of screws and they always work themselves loose. I wonder what the best choice would be for a non-permanent Loctite type sealer to keep this from happening?

No such thing as "best". I don't want to hijack this thread too much since it's really not about this topic, but lot's of things can work...

-- Any sealant (an adhesive/sealant is even better) can work for this application to help tighten things up a bit. 4200 (just not exposed to UV), 4000UV, LifeSeal, Bostik makes some good stuff, too.
-- A plastic toothpick can work
-- A small zip tie can work
-- Recoating the inside of the screw hole with resin (possibly slightly thickened) to essentially make the diameter of the hole smaller can work. A pipe cleaner works well for applying.
-- In same cases, the next size larger screw will work
-- There's probably a dozen other methods than can work. Heck, even wrapping the lower threads with a very thin strip of duct tape can do it.

Ultimately, screws loosen over time and it should be considered normal practice to check them periodically and redo the sealant if needed.