PROJECT BOAT - RELEVANCE OF SUBSTRATE WOOD ROT

[COOPER W NORMAN]

1989 SEA RAY 210 BOWRUNNER

Does it matter when the original wood substrate rots -- originally serving as the form on which the fiberglass hull was overlaid? In my case, this rotten wood that concerns me is in the transom, beginning low at the drainplug fitting. The fiberglass hull shows no signs of cracking or distress and there is no engine mounted on the transom or significant engine load transferred into it -- the inboard block and transmission are all anchored and supported on engine mounts secured to interior structure that appears solid.

Do I understand correctly?

Sea Ray constructors laid up the original glass and epoxy resin hull over the wood substrate, but after the fiberglass cured it became the structure and developed sufficient strength to serve as a hull without any dependency on the wood formwork temporarily needed to support the fiberglass during construction. Does that wood, an artifact of the construction process, serve any useful -- that is, structural -- purpose?

The Details

1989 Sea Ray 210 Bowrunner with GMC 4.3L V-6 Inboard and Mercruiser Alpha 1 -- Mechanically flawless and utterly dependable. First project boat: Great fiberglass hull and great mechanicals -- except, beneath the hood, the interior plywood forms beneath the floor were no longer reliable -- originally installed to retain floatation foam during construction -- and provide mechanical attachment points for floor deck and other items. In mine, the floor deck was spongy and all that under-deck wood was rotten; so I cut it all out and replaced it with treated plywood this time and installed new carpet throughout. Good and solid, if a tad heavier than original. And this spring, completed the interior upholstery job replacing all the seat and vinyl trim pieces.

Looking good and fit, we enjoyed the fruit of this labor this summer -- until i discovered that the transom is apparently rotted inside, beneath the fiberglass hull. Localized at the drainplug area, where it apparently leaked around that fitting.

Am now faced with major service to the Mercruiser lower end -- pump impeller and lubrication, boots, etc. and contemplating whether the rot issue undermines further investment in this boat?

Thanks for your thoughts.

 

[BillK2632]

Sea Ray constructors laid up the original glass and epoxy resin hull over the wood substrate, but after the fiberglass cured it became the structure and developed sufficient strength to serve as a hull without any dependency on the wood formwork temporarily needed to support the fiberglass during construction.

That's a pretty general statement and probably holds true for a lot of the construction of a small boat like this. Most of the smaller SeaRays, especially newer ones are solid fiberglass, almost no wood and no coring in the hull and deck. The one exception is the transom - the wood rot you are referring to is the coring - a piece of wood sandwiched between an out and inner layer of fiberglass. This coring provides the majority of the structural strength in the transom without the weight of multiple layers of fiberglass. the transom is apporx 2-3inches thick.

So here are the issues you have:

• The rotten coring is only going to get worse.
• Eventually the transom will weaken to the point you will get flexing around where the outdrive is mouted (the transom assembly) and eventually leaking. This could take months > years depending how much the boat is used and if it is dry stored or stays in the water.
• The fix is common, but involved to do it correctly. Engine has to come out, transom assembly removed, then you cut the inner layer of fiberglass off, replaced the wood coring (or use a synthetic board material that will never rot). Put a new layer of inner fiberglass on and your done - you usually put the one you cut off back in place and glass it in. If you have the skills to replace the flooring, you could do this also.
• A cheap fix would be to drill a series of holes to determine the extent of the rotted area, then inject an epoxy into the holes to firm up the rotted core. Given that age of this boat and if the rot was limited to a fairly small area, I might consider this.
• Or do nothing, but eventually you will start seeing flexing around the outdrive (cracks in the gelcoat) and then leaking as the core rots more.
• It's pretty common for a boat of that age and vintage to have some rot issues, especially in the transom. If you like the boat and can do it yourself, it is worth the fix. To pay to have it done would probably exceed the value of the boat.

Sounds like the root cause of this is the sealant in the drain plug failing. Periodically every screw or bolt that goes through a cored hull or deck should be checked and re-sealed. $1 of caulking probably cold have prevented this. But I can't say that I have checked the same on my 19yr old boat. I did check and reseal the transducer.

 

[scoflaw]

Also the stringers that your engine is mounted to also attaches to the transom. Looking at that pic it does not look like an easy fix. I'd sell it and buy a boat without rot issues.