Rudder 'plate' leak / caulking - Maxum Boat Owners Club

Dhalter · 08-10-2020, 11:24 PM

Hi everyone,
I have a 1998 3700SCR with twin 7.4s and V-drives - now halfway through second summer - 170 hours in!
Absolutely love the boat, but have been chasing a bilge leak that more annoying than anything. I finally found it this weekend when changing out the water pressure regulator (another story).
Both rudder mounting plates are leaking. I tightened the nuts up on both sides but it did not stop the leak.
A few questions as I think these have been leaking for awhile:
Is the transom wood cored? From what I can see I would say no - concerned about rot. I tapped with a small hammer and it is solid, but...
Second, has anyone ever had this problem? I did a search and came up empty.
Has anyone ever pulled them for a re-caulk? Doesn't look too bad actually.
Thanks

mmwjr · 08-11-2020, 12:15 AM

Most rudders penetrate the bottom of the hull and not the transom, so you have the transom style? If so I suspect the transom does have a wood core. Either way the boat needs to come out of the water to remove the rudder mounts so they can be re-bedded. At this time you can look in the holes to see if there is wood that may be rotted which would lead to a leak since it could not support the compression of the clamping force of the mounts.

Dhalter · 08-11-2020, 01:48 AM

I have the transom plate style. 8 bolts hold it to transom, 9/16 inch nuts with what looks like 1in washers. Transom looks one inch or so thick - not thick enough for a core. Will take pics tomorrow.

mmwjr · 08-11-2020, 02:07 AM

Quote:

Originally Posted by Dhalter

I have the transom plate style. 8 bolts hold it to transom, 9/16 inch nuts with what looks like 1in washers. Transom looks one inch or so thick - not thick enough for a core. Will take pics tomorrow.

One inch thick would have a core.

shrew · 08-11-2020, 02:01 PM

Transom mounted..?? That is interesting. I don't know that I've ever seen a transom mounted rudder on a power boat. How does the linkage penetrate the transom?

mmwjr · 08-11-2020, 03:32 PM

Quote:

Originally Posted by shrew

Transom mounted..?? That is interesting. I don't know that I've ever seen a transom mounted rudder on a power boat. How does the linkage penetrate the transom?

There is a cutout for a steering arm (tiller) just like an I/O has.

Dhalter · 08-13-2020, 01:02 PM

Here are pics of both sides. A bit of crush / cracking around the washers, but otherwise not too bad. More of an ooze than a nothing. Will wait for the fall to pull and remedy. Differing accounts of core of not - local marina says no, and they have done this job (so they say). I will find out for sure when I pull them out. I will clean up the fiberglass and may even add a stainless sandwich plate instead of the washers. Will document.
Every large Maxum with innards I have seen has this rudder configuration.

Dhalter · 08-13-2020, 01:05 PM

Here is view of rudder when the boat was out off the water.

mmwjr · 08-13-2020, 04:39 PM

I recommend you add a bonding wire to these that is connected to the rest on the thru hull bonding system.

Dhalter · 08-14-2020, 01:40 AM

Bonding wires are there, both sides. Thanks though - those wires are important.

mmwjr · 08-14-2020, 12:23 PM

Quote:

Originally Posted by Dhalter

Bonding wires are there, both sides. Thanks though - those wires are important.

Ok Now I see them on bottom bolt.

Glenn111 · 08-14-2020, 09:45 PM

I'm like Shrew...never remember seeing a transom mounted rudder. Not that way on the 41 or 46 ft models or direct/Vdrive Sea Rays I owned. Seems to me if the transom had a leak for any length of time and was anything but solid fiberglass/resin, then you would have very noticeable "soft spots" around the mounts. Good luck on securing the hardware.

Dhalter · 11-11-2020, 01:00 AM

Finally completed the repair of the rudders.
- Removed all bolts and nuts.
- Cleaned out all caulk.
- Caulked and installed New stainless 3/8 carriage bolts.
- Created templates and cut 0.188in 316AS plates with slots for the rudder links
- Removed all linkages
- Cleaned and ground fiberglass flat
- Caulked inside surfaces and plates with 5200.
- Installed.plates with new 3/8 stainless nylon nuts.

Overall turned out nice.

Glenn111 · 11-11-2020, 01:46 PM

Really nicely done! Looks SOLID. Did you confirm core or solid transom.

Dhalter · 11-11-2020, 10:20 PM

I was not able to confirm. I will be pulling the U-bolt to the left in the lower pic to seal that up (not currently an active leak but why not). Might be able to confirm then. I would assume it is wood cored.

Fortunately the leak was at the plate / transom interface and not the through-bolts so core should not be compromised.
I heard no hollow sounds during rap test or water readings with the meter. So should be good to go.