Humminbird SI transducer mounting bolt torque

[Bob G.]

Earlier this year the SI transducer for my 1198 that is mounted on the bottom of the hole shot plate was loose and hanging down. I originally mounted the 1198 and transducer in 2013 and have had only a few times that it was loose. I found that one of the square nuts was missing. Not sure how that happened considering the nut fits into a square spot on the back of the transducer. I got a square nut at the hardware store. Could not find a SS one but used it anyways. I tightened the two bolts after leveling the transducer. The bolts had threadlocker on them. I pulled the boat out of the garage to work on my boat in front of my house. I saw the transducer hanging down and it was broken at the ears. I ty-wrapped it to the steering hoses and used 2D sonar until I got a replacement.

I purchased a used SI transducer from a BBC member and installed. A couple of trips the SI image wasn't good and saw that the transducer was loose. I tightened it again. All parts including the star washers are installed. The SI image was not good a couple of days ago and the transducer was hanging down again.

How tight should the bolts be to keep it from getting it loose but not break the transducer? Here is a pic of where it is mounted.

DSCN2354_SI_Transducer.jpg

[bobcoy]

I would guess a little tighter. I have never had a problem with a transducer coming loose. I would suggest Locktite blue thread locker and just a bit tighter than before. Bob
I sold my 1197 and 1198 a few years ago and gave the documentation with them. I would be suspicious the nut you bought was the correct one for the screw. I would try to find the proper hardware. I know its a tough ask ,but someone may still have the bag of hardware because he used the original hardware for the replacement.

[Bob G.]

I would guess a little tighter. I have never had a problem with a transducer coming loose. I would suggest Locktite blue thread locker and just a bit tighter than before. Bob
I sold my 1197 and 1198 a few years ago and gave the documentation with them. I would be suspicious the nut you bought was the correct one for the screw. I would try to find the proper hardware. I know its a tough ask ,but someone may still have the bag of hardware because he used the original hardware for the replacement.

Thanks for the advice. The used transducer came with all of the hardware and I used it. The bolts had the original threadlocker on them. I'm going to add more blue thread locker.

[bobcoy]

Make sure all metal is clean and dry before applying the locktite.

[Bob G.]

I put it together with blue loctite. We’ll see what happens the next time on the lake.

[Bob G.]

Well, won't have to wait until I go on the lake tomorrow. I went down to my boat garage to put the plug in and the SI transducer was missing from the mount. It was hanging by the cable, the ears broke off. This is the second transducer that broke this season.

I'll be fishing tomorrow without SI at the console and won't be finding any new offshore structure.

Somewhere between not tight enough and too tight must be a happy medium to keep the transducer just right.

I used blue loctite when I put it back together the other day. The original bolts come what looks like red RTV on the threads. I wonder if it would be better to put RTV on the bolt threads and let them dry before installing. Any thoughts?

EDIT: After searching the web, I think the red stuff on the threads is a pre-applied thread locker. Most likely Loctite 202 or something similar.