Engine mount lag bolts

[Mastercraft]

I asked the factory this two days ago without a response. Does anybody need to tighten up their engine mount lag bolts often? My 2017 R29 need the engine mount lag bolts tightened every 50 -100 hours. Engine has 1100 hours. Existing lag bolts are 3/8 x 2 with 5/8 head. One was stripped, so I put 1/2 x 2 with 3/4 head. How long can I go before I hit the fiberglass outer skin of hull? What material is the bolt grabbing? I dried it out with a hair dryer on low and put RTV in hole then put lag bolt in. Roughly how many ft-lbs on bolts? Just for some idea to know if super tight is required. I did not shift engine.

 

[Red Raven]

I asked the factory this two days ago without a response. Does anybody need to tighten up their engine mount lag bolts often? My 2017 R29 need the engine mount lag bolts tightened every 50 -100 hours. Engine has 1100 hours. Existing lag bolts are 3/8 x 2 with 5/8 head. One was stripped, so I put 1/2 x 2 with 3/4 head. How long can I go before I hit the fiberglass outer skin of hull? What material is the bolt grabbing? I dried it out with a hair dryer on low and put RTV in hole then put lag bolt in. Roughly how many ft-lbs on bolts? Just for some idea to know if super tight is required. I did not shift engine.

For what it is worth I have a 2014 R27 with a Volvo Penta D3-200 and the the Volvo Penta installation instructions list the engine mount lag bolts as 30 ft lbs and the top nuts above as 48 ft lbs. I hope this helps.

Curt

 

[TristenT]

I haven’t noticed needing to regularly tighten the mounting lag bolts on my D4 but have bumped them up a few times it’s really hard to go with a torque spec for something like this. I go with good and tight use your best judgement on tightness consider that the lag bolts are just screwing into wood so don’t put out too much on them.
If you have one stripped out the proper way to fix it is to drill it out larger until you get dry wood then epoxy in a new wooden dowel then set the lag bolts into that. You want to try and seal the top to avoid getting moisture down the bolt causing the wood to rot.
Another option with the same size bolt or the next size up like you grabbed is to clean out the hole and then mix up some splash zone, pack it into the hole then run the lag bolt all the way in. As the splash zone cures periodically twist the bolt back and forth, this essentially makes new threads once cured bump up the bolt and you are good to go.