The Rot Doctor


Subject: Thank You (engine mount repair)
Date: Fri, 19 Nov 2004


Just wanted to say thank you for guiding me thru the process of repairing the stainless lag engine bolts that no longer tightened in the stringers on my 1983 Mastercraft ski boat that I've had since new.

I first wanted to get familiar with the CPES & L&L products using a block of wood and to determine what my options were.

Option #1: To reform the threads in the wood with the epoxy and reuse the lag bolts.

Option #2: To epoxy into the stringers stainless threaded studs that would remain there for good. Removing the engine would be accomplished by removing SS nylock nuts on the studs.

To determine which option had highest strength, I got a block of wood & drilled a 1/2" dia x 5" deep holes to simulate the existing holes in the stringers.

I treated all holes with cpes. Then filled several holes with the L&L, let cure, then drilled a pilot hole & screwed in the lag bolt . Holding strength wasn't good. Strength was determined by using a torque wrench to see how much torque was required to break the bolt/stud free.

Then I did the same & inserted a threaded stud into the hole while the L&L was uncured. Let cure & the holding strength was greatly improved and even higher with adding your sawdust to the mix. Hence Option #2 was the way to go.

I dug out as much "loose" dark soft wood in each hole as possible & used a shop vac to remove the loose particles. This left me with an internal cavity at each motor mounting point. I had special SS hanger bolts made so that they could thread into the remaining wood & leave a 3/8"-16 machine thread protruding from the stringer. Each cavity was treated with cpes twice over a 2 week time period. Then I injected the L&L multiple times to fill the cavities over the course of several weeks. The studs are now hopefully in for good. Time will tell. I took the boat to my local dealer to have the engine re-aligned & he commended the epoxy project.

Thanks again for your support.

Greg S.


Many thanks for your testing, and for reporting the results...and for using our products! It's much appreciated.

The addition of wood flour or sawdust greatly increases the ability of the L&L Resin to accept screws and lags, and hold them securely. This is why we always recommend that the sawdust be added -- at least I hope we do!

Thanks again, and have a happy Thanksgiving Holiday.