Stern Drive SeaCAST Transom Rebuilding Advice needed

[rocketboy52]

I have a Winner Viscount with a Mercruiser 888 Pre alpha stern drive with a 302 ford motor. I have been working on overhauling this cool boat, and a bad water leak caused me to haul out the motor. Once I hauled out the motor, I found that my Y pipe was cracked and my transom plate was snapped in two.

Everyone that responded in a previous posting told me I needed to check the transom, so I drilled a few holes and found that my transom in certain areas is indeed dark like coffee grounds color, even though the transom looks, sounds, and feels solid.

I’m looking at rebuilding the transom with seaCast, but in this boat, I’m not sure how far I should go to replace “all wood”. The transom wood is not Sandwiched, meaning it doesn’t have an inner glass skin, but rather is Glass – Wood – Paint from the outside in. If you look at the attached pictures the Green area is the thickest part of the transom, and actually has a second ply of wood laminated in this area to get the needed thickness for the stern drive unit (2” thick) I drilled multiple test holes to see where the wood was dark and the only areas that were dark were holes n the Green area (holes A, B, and C) The holes I drilled at D, E and F looked like clean new wood. My question is should I just replace the thickest part of the transom (green highlight) with a SeaCAST transom, or do I need to cut into the sealed bunks and rip out all wood (Red out line) to do this project right?

I want to fix this prject right, but I also don’t want to go overboard wasting time and money if it is over kill. Those who have replaced transoms before what are your opinions? What would you do? How do you prevent transom rot in new boats? Thanks in advance.

 

[Mark42]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

Seacast will be difficult to use without an inner fiberglass skin. It is intended to be poured into the hollow left when all wood is removed.

The next question you will be asked is how are the stringers down near holes E, C & B. Reason being is that usually when there is transom rot down there, the stringers are rotten too and need replacing.

You may have an advantage that there is no inner fiberglass skin on this boat, so rot did not travel too far.

Some people will disagree with me on this, but I think if you are able to cut out just the green area, and all surrounding wood is white and dry, AND the stringers are dry, you could get away with fitting in a new piece. A larger inner "plate" would be needed to overlap the green into the red to give the proper support. Maybe a small router or dremmel tool can be used to make the cut from the inside without cutting through the outside fiberglass layer.

The reason I say a patch may be an option for you is because the i/o does not rely only on the transom to support the engine thrust. Much of the force is handled by the engine being mounted on the stringers. So if you find conditions favorable, I don't see why it cannot be repaired rather than replaced.

If the rot extendes outside the green, replace the whole transom and stringers as needed.

 

[sdunt]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

The lack of an inside fiberglass skin does give you more options.

yes, the Ideal - perfect world way to repair this is a complete transom replacement. Marks suggestion of a partial replacement could work. The big question is how bad is the damage.

You will need to structurally attach your 'patch' to the rest of the transom. If the plywood is multiple layers you could 'step' the edges of each layer, the inner layer is smaller than the other layer. Also laminating fiberglass over the area will strengthen as well as possibly use aluminum angle or channel screwed and bolted accross the entire transom.

As a carpenter / cabinet maker, I am not coming up with much you could use to mechanically attach the new 'patch' to the existing transom. Mainly because you are filling in a 'hole' If you could slip that 'patch' down in from the top you could use dowels, or slines and grooves, etc to mechanically attach the two and increase the glue surfaces.

Based on the nature of this repair I would use a slow setting epoxy behind the patch and also around the edges.

Use the brass tubing technique to isolate the bolt holes once you have the repair done:

go to good ACE/TRUE VALUE hardware or hobby shop that sells K & S tubing..

buy a piece of tubing with an ID size that is two to three sizes bigger than your bolts.. but is still a common drill bit size on the OD..

bore holes thru the transom and install the tube all the way thru the transom, coat the outside of the tube with epoxy before you install the tube, you want to cement it in place and seal it and the wood you just punched a hole in.

As you install the bolts, shoot caulk/silcone in the tube in between the bolt and the tube to water seal 'the hole in the boat'

the tube isolates/seals/protects from water infusion and isolates it from EVER soakin' into the side walls of your new transom. Kind of like making a drain plug hole but for the motor mounts or any other holes in the transom."

 

[sdunt]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

Ok, my brain finally kicked in on how to mechanically attach the "patch".

Lets look at this like you would handle a fiberglass repair. In a fiberglass repair you would grind out the bad material in the center of the repair and taper the edges, now for woodworking tapers are hard to handle, but steps are not. Taking off on Marks comment about a router.

How about if you use MANY thin pieces of plywood to fill in the hole each one larger than the previous? You can use a router and fence or guides to cut, for example, 1/2 inch deep by 2 inch wide steps for each suceeding layer of the transom. Also since you can modify the depth setting of the router, you could:

Cut all the way down to the outside layer of fiberglass. Put in a layer of fiberglass cloth with epoxy and 1 layer of 1/2 or thinner plywood that fits the hole. Fill in the edge gaps.

Set the router to cut to the same exact depth as the top of this new plywood. Route a 2 inch wide step all around the patch. Use guides - boards screwed on to control how wide you can router. Add another layer of fiberglass cloth and epoxy sized for the new opening. Add a layer of 1/2 plywood on top of cloth.

Re adjust router to match the top of the 2nd layer of plywood and router out a 2nd 2 inch wide step. Glass and epoxy over that and add additional layer(s) of plywood and fiberglass.

The final layer of plywood will probably stick up above the surrounding wood, because we added the layer of glass at each level. But you can glass over the entire area and have a very strong laminate..

Good Luck

 

[gspig]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

I replied some in the Winner section. Those pictures here help a lot. My boat has the I6 engine, the stringers that your engine mount to on my boat are just fiberglass, no wood. My guess is that your transom may have been replaced before, my transom was glassed inside. Use a rubber mallet and sound the rest of the transom outside of the area you marked with green, if it rings then it is probably good. You may be able to get by with just replacing the green area. If you want to replace the entire transom, the good news is that the boxed area under the floor is just a cavity filled with foam. Bilge side of the box is not a structural element for the hull, it just supports the edge of the floor. I cut the box and floor open under the rear deck area to have room to work. I also reglassed the stringers all the way back to the transom.

 

[tommays]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

Its a merc sterndrive and it will be putting the FULL stress into the transome

Any flex will cause and alliment problem that will eat the engine couppler


Tommays

 

[Mark42]

Re: Stern Drive SeaCAST Transom Rebuilding Advice needed

Its a merc sterndrive and it will be putting the FULL stress into the transome

Any flex will cause and alliment problem that will eat the engine couppler


Tommays

Well if that is the case, then the transom had better be well reinforced if its being patched.

If it were up to me and all that is needed is that small area, I would cut the patch piece and epoxy it in place. Then after the i/o parts are fit in, put another plywood piece over the patch extending as far left and right as possable and epoxy that in place too.

Although when all is said and done, it is probably better to just replace the entire transom and epoxy a new one in. Make sure large epoxy fillits are used at the outer left and right ends of the transom where they meet the hull so all that thrust has a good hold to the sides of the boat.

 

[easyfix]

Hi. I Have a 28ft Bayliner 2855. I used Sea Cast and it worked out great. I went over every option I could find for months and months. There are many ways to skin this cat. I have a V8 with an Alpha outdrive as well. I just had to figure out a way to pour the sea cast into my boat. I made a video about it. It wasn't too bad to do at all. I hope this will help you out. I loved the results.
~Shaun
https://youtu.be/uRD0YNoCYQA

 

[GA_Boater]

Hi. I Have a 28ft Bayliner 2855. I used Sea Cast and it worked out great. I went over every option I could find for months and months. There are many ways to skin this cat. I have a V8 with an Alpha outdrive as well. I just had to figure out a way to pour the sea cast into my boat. I made a video about it. It wasn't too bad to do at all. I hope this will help you out. I loved the results.
~Shaun
https://youtu.be/uRD0YNoCYQA

The OP asked for advice 12 YEARS AGO!

Closed.