Mast Step Leak
Hi Jimlay, similar problem with our boat some years ago. Following is an article that I wrote about it.
"While Belle-Vie was on the hard for repairs awhile ago with the mast unstepped I addressed a number of minor maintenance issues including a small leak through the mast step into the salon.
The mast step is held in place with four SS flat head through bolts with lock nuts. This step has a drain hole on the head end bottom side so that rain water entering the mast head can drain out through this small hole at the bottom. The electrical wires run through a short piece (original was two inches long) of one inch plastic PVC pipe that is inserted in a hole in the coach top. You can see this piece of pipe if you remove the covering from the top of the compression post.
The pipe is supposed to be sealed, but over time this seal failed, so water coming from the mast head would leak around this pipe and into the salon. The PO tried to use Silicone II from inside the boat but that did not work.
After cleaning the cast aluminum step plate and coach roof surface I used 3M4200 sealant to rebed the plate. The new three inch piece of PVC was placed with a liberal amount of 3M4200 around where it entered the coach roof. The PVC pipe extends about two inches above the coach roof so that any rain water pooling at the base will run out through the weep hole in the step plate. Be sure to leave a drip loop in the wires that enter the coach roof.
Each season I use a pipe cleaner to clear out any debris in the step plate weep hole. This repair was done in 2002 and it still remains dry."
It is likely your leak is coming from rain water pooling around the mast step and then overflows through the wire chase conduit that extends through the coach roof. Check for the small weep hole in the mast step plate that allows rain water to drain, make sure it is clear. That could be your source.
During our cruise this year, in a heavy rain, water began flowing down our compression post. First time since 2002. Went out with a pipe cleaner and sure enough the mast step plate weep hole was clogged with gunk. Cleared it and water came pouring out.
It is nice to know that the repair I did back in 2002 remains in good order. Usually I clean that hole every season, but alas, it had been more than a year.
If water is coming in from around the conduit, rather than through it, about the only effective repair, is unstepping the mast and doing what I did, IMHO.
Let us know what you find out.
