1972 F25 Rudder Shaft Board

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1972 F25 Rudder Shaft Board

Post by vabeach1234 »

While out of the water for engine replacement, I noticed the board that spans between the two main stringers at the stern of the boat that the rudder shaft goes through was loose. The board is attached to the top of the stringers with 2 lag bolts at each stringer. So I tightened them down.

I went fishing this past saturday (got some nice striper, YES!!!) and on the way back in I noticed a loud continous noise at around 2600 RPM and higher. I opened the engine hatch and noticed that the rudder shaft support board was vibrating and making the noise. I'm gonna try to put some rubber bushings or rubber spacers (probably from an auto parts store) between the board and the stringer to try to stop the virbration.

I was wondering if anyone has come across this in there F25 or other trojans, or is this just a unique thing on my boat (I wouldn't be supprised if it was). Your thoughts...

1972 Trojan F25 Express Hardtop
FWC Chrysler 318 V-drive Paragon Trans.

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Lag Bolts

Post by Paul »

Hi Ken,

I dont believe isolating the board with rubber is the way to go here. This board is what helps stabilize your rudder and keep you in control. This board coming loose is most likely the effect of a problem somewhere else. Ckeck the condition of the stringers where the lag bolts are. You should be able to bolt the cross board down "tightly" without stripping the threads. If the threads feel like they may or do strip, there's a few of options for repairing this.

Worst case, if the stringer if badly rotted, is to replace the affected section of stringer. If the bolt holes are a little soft, there are two ways to solve this problem. One is to dry the hole, inject it with epoxy, drill a new pilot hole and replace your bolts. The second one, my prefered method, would be to obtain a piece of hardwood dowel at least twice the diameter of the bolt. Then using the oroginal hole as a pilot hole, drill a hole big enough to insert the dowel into the stringer a little deeper than the depth of the bolt. Now epoxy the dowel into place, drill a pilot hole and reinstall the bolt.

If the stringers check out OK, then inspect the rudder itself for any damage that may cause enough vibration to loosten the board.

Hope this helps
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Post by chucka »

Paul's advice is 100% right. A loose upper bearing places way too much stress on rudder shaft stuffing box. This needs to be secure. The only thing I would add is if you drill & fill the holes with epoxy, mix in a heavy dose of chopped fibers, not straight resin. Let it cure fully before re-installing the bolts. If you epoxy the bolts in place, they will be nearly impossible to remove without snapping them off in the future if you ever need to get at the rudder stuffing box. I speak from experience on this :oops:

[If the bolts do get epoxied in place, you can try heat to get them loose, but they are so long its not easy to get the heat down to the threads where you need it.]
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