motor trim tabs falls off--twice! SOLVED

[Home Cookin']

Yesterday morning I noticed my trim tab on my motor was gone. Bolt was still there. I had been fishing the night before; guess it vibrated loose. So I bought another (about $35!) and put in on. I left the cap off the bolt cover in case I needed to adjust it. Tightened it with a socket on a driver. Ran fine; went fishing again and returned after dark. This morning I went to retighten the bolt and replace the cap--gone again! As was the bolt!
So when I put my now $70 trim tab on, any suggestions? I seriously might put cable ties on it, temporarily, and check it a lot to see what's going on.
What about a lock washer, too?
I don't want to put anything on the threads since its already mis-matched metals (SS to zinc)

The boat is in the water at the house so it's not being stolen.

Is this typical, unusual, or highly unusual? it's been on for 2 years/220 hours, although I did replace the prop a couple of months ago.

150 Yam 2 stroke, all Yamaha parts.

Thoughts? Thanks--and happy fourth!

 

[robert graham]

Re: motor trim tabs falls off--twice!

Re: motor trim tabs falls off--twice!

I've heard these zinc trim tabs were known for falling off, but I've never lost one. Maybe remove it, clean bolt threads good with wire brush and carb cleaner, then use some Loctite on threads and add a lock washer. That bolt that holds it on is sorta down in that hole, so how you suppose it got up out of there?...maybe water pressure blew it up and out while you were running? Good Luck!

 

[Home Cookin']

Re: motor trim tabs falls off--twice!

Re: motor trim tabs falls off--twice!

I think water pressure blew the bolt straight up, b/c the first time the bolt stayed on, but the cover was over top of it. It is down in a hole.
Funny I didn't notice any difference without it; makes me question its importance. Since I leave the motor up, it's not doing much as a "sacrifice."

 

[Frank Acampora]

Re: motor trim tabs falls off--twice!

Re: motor trim tabs falls off--twice!

Drill the tab to clear the bolt, buy a longer bolt, and use a nylock nut inside the hole in the leg. You will have a bolt head sticking down unless you can find a flat head bolt or countersink the head, but that won't be much drag at all.

 

[Home Cookin']

Re: motor trim tabs falls off--twice!

Re: motor trim tabs falls off--twice!

When I went to get #2 a different guy behind the counter said Yamaha has a bulletin out on this: While you are tightening the bolt, you have to tap the center of the tab with a hammer to get it seated. Otherwise (and what happened) is that it feels tight, but it's not, and quickly vibrates loose. this explains why a new one falls off right away; the old one falling off is just what happens sometimes.
They said with that, I shouldn't need a lock washer, but I'm still thinking about it.
Another guy suggested that I put the top of the threaded hole flange in a vise and tighten slightly, to make the round hole a little eliptical, so it will hold tighter. I'm not sure about doing that.

I'm still going to put cable ties on it for the initial run if I can so that if it works loose I can maybe catch it before it comes all the way off. But there's a lot of force going on down there, I know.