How to test I/O motor mount stringer for rot?

[fishnfiend]

New to me '86 SeaRay with Merccruiser 140 I/O. Floors are shot, I'm going to replace them this winter.<br /><br />The motor mount stringer appears to be about a 4" x 6" piece of lumber sitting crosswise in the bilge. Top is covered with fiberglass which is intact. Reaching under the stringer, however, I can feel that the manufacturer stopped the glass at the outside edges of the stringer - the bottom feels like exposed wood. Hopefully it's sealed someehow. It FEELS dry, and I can see no visible sag, but how do I test for any rot so I know that this piece does not need replaced? In my mind, this structure is too important to allow uncertainty about whether it's OK or not.<br /><br />What say the pros? Do I drill a hole in it and look at the wood drillings? Are there measureements I could take to know whether it's sagging?

 

[djzyla1980]

Re: How to test I/O motor mount stringer for rot?

You can drill a hole and look at the shavings, or you can try to tighten the motor mounts. If there pretty loose... or keep tightening with out really getting tight chances are there rotten.<br /><br />If you are going to replace the floors the stringers would be present. If it were mine I would probably go ahaed and replace those even if they don't look like they need it. Soak. and cover with fiberglass so they will be more water reistant.

 

[Boomyal]

Re: How to test I/O motor mount stringer for rot?

I would remove the lag bolts and probe into the side walls of the lag holes. It would be quickly apparent if the wood is rotted around the holes.<br /><br />If the wood is sound, I would pour penetrating epoxy into the holes until it takes no more. Do it repeatedly as required. Depending on how your boat is constructed the outer bolts may only go thru 1 1/4"s of wood. <br /><br />If your lags show deterioration on the threads, replace them with stainless. You can go 1/16th bigger on the main bolts if the hole is stripped but otherwise sound. You may need to enlarge the mount feet holes if you do that. Be sure to stuff the holes full of 3M 4200 before you thread them back in. One of the biggest oversights of the Mfg'rs is that water follows those lags right down the holes.