Rocket launcher

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#1
I'm about to install the rocket launcher on my 228. I would like to know what size bolts are used to secure it to the hardtop. Are they 5/16" or 3/8"? I know there are 3 bolts on each tab.
Thanks in advance.
 

Fishtales

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#4
A couple of tips.
- Mark twice and drill once (kinda goes without saying)….
- You could drill a size bigger and install a piece of plastic tubing that has the OD of the hole you drilled and the ID of the bolt you are using. This gives you the ability to seal the inside of the drilled hole.
- Use nylock nuts on the backside. Use marine SS hardware to mitigate rust.
- Use plastic flat washers between dissimilar metals. Between flat SS washers and aluminum mount for instance. This will mitigate corrosion.
- Seal the installation well with a good quality caulk. The coring of the hardtop may be balsa and you don't want water intrusion.
 
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#5
A couple of tips.
- Mark twice and drill once (kinda goes without saying)….
- You could drill a size bigger and install a piece of plastic tubing that has the OD of the hole you drilled and the ID of the bolt you are using. This gives you the ability to seal the inside of the drilled hole.
- Use nylock nuts on the backside. Use marine SS hardware to mitigate rust.
- Use plastic flat washers between dissimilar metals. Between flat SS washers and aluminum mount for instance. This will mitigate corrosion.
- Seal the installation well with a good quality caulk. The coring of the hardtop may be balsa and you don't want water intrusion.

Thanks for the advice . You meant mark 10 times before drilling . I'm well aware that sealing is very important as water penetration will rot the hardtop core even if it is not wood ( composite ).
I know I can use bigger bolts , the reason for asking , I think the bolts GW use would be more than adequate.
If anyone could be bothered to check theirs I would appreciated very much.
Of course I'll use 316 marine grade bolts and 2 nuts a normal open nut and a captive nut so you don't rip your arm on a sharp bolt hanging down. I always isolate S/S and aluminum with nylon washers and coat the screws/nuts with this product .
Duralac Jointing Compound 115ml


I use sikaflex 291 to seal all core penetrations .

 

Fishtales

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#7
Ahh. Didn't know you were drilling the flat metal as well. My boat isn't avail to me now, so I'm no help. I would say 3/8", (3) per flat piece should be plenty strong enough.
If you can do a back plate that would be good. The factory doesn't use one, just large washers as I recall.
 
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#10
My bolts are 1/4 x 20's on my launcher.
Thanks KY, what do you mean 20'S. What size are the washers ?
I was going to use 5/16" but if GW uses 1/4 I would think that is sufficient. I know GW don't use plates even on their rod holders. On the newer 228's they have S/S plates on the outboard bracket, I wonder when they started using them, maybe when they rated them 300hp? My old boat only had 6 bolts the new one has 12 and 4 plates.
GW transom bracket.jpg
 

seasick

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#12
Thanks KY, what do you mean 20'S. What size are the washers ?
I was going to use 5/16" but if GW uses 1/4 I would think that is sufficient. I know GW don't use plates even on their rod holders. On the newer 228's they have S/S plates on the outboard bracket, I wonder when they started using them, maybe when they rated them 300hp? My old boat only had 6 bolts the new one has 12 and 4 plates.
View attachment 7053
In this picture you see what happens to bolts (stainless) when there is moisture but not a lot of air (oxygen). Stainless will rust in an environment of moisture but not a lot of air. That is why the rust seems to be seeping out from under the backing plates. The point is that you need to not only seal the holes from moisture but also you need to seal the hardware too if not exposes to the air.
 

Ky Grady

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#13
Thanks KY, what do you mean 20'S. What size are the washers ?
I was going to use 5/16" but if GW uses 1/4 I would think that is sufficient. I know GW don't use plates even on their rod holders. On the newer 228's they have S/S plates on the outboard bracket, I wonder when they started using them, maybe when they rated them 300hp? My old boat only had 6 bolts the new one has 12 and 4 plates.
View attachment 7053
What Dennis said is what I was referring to. I have 3 phillip oval head machine screw with finish washer on each plate holding the launcher on with fender washers, which are a little larger than standard flat washers, and nyloc nuts.
Screenshot_20190415-104353_Gallery.jpg
 
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#14
In this picture you see what happens to bolts (stainless) when there is moisture but not a lot of air (oxygen). Stainless will rust in an environment of moisture but not a lot of air. That is why the rust seems to be seeping out from under the backing plates. The point is that you need to not only seal the holes from moisture but also you need to seal the hardware too if not exposes to the air.
That was one of the reasons I took the livewell out . To inspect the transom bolts and the through hull bolts on the livewell and raw water pick ups. I already covered all the bolts with Sika.
The other problem with this newer boat is the deck plates on the sides ( not floor plates) are different to the older boat and I don't like the way they hold on , I think I'm going to change them at some stage to proper screw ins. I don't mind the pop outs they use on the floor, they never fall out and if you change the O rings every few years they don't even leak.
All other changes in the newer boat are improvements I think.
Thank you to all that replied with advice.