View Full Version : More Stringer repair talk (3/4" hard wood plugs)

06-23-2009, 04:12 PM
Using Bellinghamsters stringer asessment:

(copied below)

For stringer assessment you're looking for (or hoping not to find), roughly in order of progression as a boat ages

1. Wet stringers - the original layup didn't completely encapsulate the wood well, so water can get in under the glass and soak into the wood, usually from either end of the stringer, or where the cutouts for the mounts are. This is accelerated greatly if the stringers get submerged (boat stored outside with the plug in, or in the water without a good cover and bilge pump). Look for exposed end grain and see if it's wet.

2. Delamination of the glass from the wood stringer - this usually occurs after the wood soaks up water. Thump on everywhere you can reach with a hammer (hard enough like you're tapping a finish nail) and listen for differences - a good bond with good wood underneath should sound "sharp", a hollow "thud" means something is squishing under there.

3. Engine mount bolts wet/rusty/stripped - unscrew one from each mount and see if they are wet/rusty/rusted off. Poke a screwdriver down the hole and see if it's mushy/wet inside and if you can feel any defined threads in the wood. Put the lag bolt back in and see if it tightens back up or just spins (my wild guess is it should torque at least 30-40ft-lbs) If dry and solid it should be good for at least another 10+ years. If wet but will hold torque (assuming all else is good), probably 2-5 years before you'll have to do surgery.

4. Deformation (compression) of the stringer under the mounts - . In the pics you posted, the wavy "skirting" under the mount looks more like poorly layed up glass rather than something that popped loose under compressing mounts, but hard to tell if not seeing it in person. Check to see if the top surface has "sunk" where the mount lands. Also, you can check engine alignment, but it may have been realigned to compensated for the sinking mounts. Hammer around the area under the mount (sides of stringers) as described in #2 above. Once the stringers start to crush, there's no good option but to tear in and replace everything.

If they're not wet, they won't rot. Once they get wet, they'll never dry out (never in a practical sense - i.e. less than several years in a very dry atmosphere), and will eventually rot. Also, no repair will bond well to wet wood, and git-rot won't penetrate it. If the stringers are reasonably sound, but the lag bolts won't torque down, first you can hope that someone overtorqued and stripped them rather than the wood rotting - try oversizing the lag bolts (you may need to drill out the holes in the mounts. If that doesn't do it, you can pull the motor, remove the mounts, bore out the holes oversized (~3/4-1"), let it dry (w/ heat and ventilation) as much as you can stand (time-wise), then continue to let it dry for at least as long again. Fill the holes with epoxy and dowel that fits the hole, or possibly gorilla glue and dowel, since gorilla glue expands and requires moisture to cure... it sounds like maybe some good stuff, then pilot drill the holes (same or slightly smaller diameter as the minor diameter of the lag bolt threads) and put it all back together.

Good luck!

I have a few stripped lag bolts at the motor / transmission mounts and wet wood.

No Delamination and No Deformation.

Since all were suspect, I have drilled all 8 holes to 7/8". At this point I am back to good wood, Not soft and I can not pick it apart with a screw driver. I am preparing 3/4" hard wood dowl inserts for the holes.

I am now down to (2) big questions...

1. Since wet wood will rot. What is the best method to dry my stringers?
(Obviously Heat and ventilation) fan / heat gun? Any better methods?

2. What is the best method to secure the wooden dowels into the stringers?
I've got 2 gal of low viscosity epoxy resin from a previous boat project, while
great for bonding I'm concerned about adheasion to the stringers with the
moisture issue. I see Bellinghamster mentions Gorilla Glue. Anyone ever try it?
I can see the moisture curing being an asset, But I'm hesitant to bet my repair on
an unknown. I have also had a few folks recomend West System epoxy but I feel
as though that stuff is similar to what I already have.

06-23-2009, 04:45 PM
Once they get wet, they'll never dry out (never in a practical sense - i.e. less than several years in a very dry atmosphere)
If you simply want to go skiing, plug the holes with dowels and epoxy. If you want to do a proper repair, replace the stringers.

06-24-2009, 07:48 AM

I've been out of a boat for 10 yrs. Convinced the family that buying an older ski boat needing engine work was a good ideia. I'd like to get them out on the water before the summer has passed.

I guess I'm overthinking it, I just want to ski...

06-24-2009, 11:28 AM
Gorilla glue is good stuff. I'd reccomend it for the stringer plugs. It's strong enough to hold my swim deck to the bracket for going on 2 seasons now. Had the screws ripped out of one side when the swim deck cought a dock in rough water. I filled each hole with gorilla glue, basically just pushed the screws back into the holes, put a big rock on it to clamp it down (I was on vacation, had to get back on the water next morning) and it held waaay better than I expected.