motor mount lag bolts

[memaw777]

I have a 1978 century with V berth 260 hp mercruiser. one of the lag bolts that holds the motor mount to stringer would not get tight. When I pulled it out had some rust and wood rot everthing seems to be solid. I could'nt find any soft spots with an ice pick. I'm wondering if I should pour in some get rot or would there be a better fix.

 

[Boomyal]

Re: motor mount lag bolts

If you've got trouble with one, you probably have trouble brewing with more. Were the lags stainless steel? Could you detect signifigant moisture?<br /><br />I would re-drill to accept larger and longer stainless bolts. Pay close attention the the material coming out as you drill. If it remains to be rotten, you've got a project on your hands. If not, I would get some CPES, pour it down the holes, letting it drink as much as it will. Let it cure for a couple of days and run your bolts down. I would seal them with 3M 5200. If the problem was nothing more than water seeping into the holes, the above should remedy everything. I don't have much faith in Get Rot. It would not help anyway, if all the wood was rotten. It might help hold things in place for cosmetics but not for lag bolts.

 

[memaw777]

Re: motor mount lag bolts

Boomyal thanks for the info. The lags were not stainless did not see any moisture but the bolt had a little rust and there was some crumbly stuff that looked like wood rot. The other three bolts get fairly tight.

 

[Boomyal]

Re: motor mount lag bolts

Originally posted by memaw777:<br /> Boomyal thanks for the info. The lags were not stainless did not see any moisture but the bolt had a little rust and there was some crumbly stuff that looked like wood rot. The other three bolts get fairly tight.

I'd definitely get all stainless and even if you do not need to re-drill the other holes, I would treat them all with penetrating epoxy.

 

[hayhauler]

Re: motor mount lag bolts

I would mostly agree with Boomyal. If you drill out and find very little rot and if your probing with an ice pick doesn't show up anything, treating the wood is good preventative maintenance. I would treat the wood where each lag is.<br /><br />Changing to stainless might or might not be a good idea. If you are replacing a hardened bolt with a SS bolt it may not have the same properties. The fact that there was very little rust on these bolts on a 26 year old boat might tend to suggest that stainless is not necessary in this application. I'm not saying not to switch to stainless, I'm just saying to consider carefully whether it is a good idea.<br /><br />If what was already there wasn't a hardened bolt, switching to stainless shouldn't be a problem.

 

[Buttanic]

Re: motor mount lag bolts

Considering the lag bolts are screwed into wood (the weakest link) the difference in strength between stainless and a hardened carbon steel lag bolt is is a moot point. Fact is the carbon steel can rust and lose strength. The only reason the originals were carbon steel is it saved the builder a few cents. Go with the stainless.

 

[memaw777]

Re: motor mount lag bolts

thanks guys for your help

 

[Winger Ed.]

Re: motor mount lag bolts

With the bolt situation solved, I'd pull the outdrive and check its alignment.<br /><br />Its not a bad idea to do every few years anyway. But if the engine has settled onto its mounts even a fraction of an inch, the motor will try to missalign with the outdrive as the drive shaft goes through the gimbal bearing. Plus it gives you a chance to grease the U-joints on the drive shaft.<br /><br /><br />If its missaligned itself, the gimbal bearing will be under a lot of stress as will the big adapter on the back of the flywheel where the drive shaft plugs in. <br /><br />Upon instalation, the outdrive should just slide in and out on the 6 or so studs that hold it to the housing on the transom, that will tell you if its missaligned. On this- there is no hammering allowed, and no kicking on the back of the upper gear case either until the new drive shaft O rings are put on and you need to get it up that last 1/4 inch or so.<br /><br />Do a test fit first without the O rings on the drive shaft that hold it firmly to the gimbal bearing. And stick you fingers in the gimbabl bearing and rotate it, if it doesn't feel brand new & spin freely like a new car wheel bearing- change it.