Installing Motor Mounts to Stringer

[AaronJ]

Hey, I have a Yanmar 2GM20F. I'm going to replace the flexible mounts. Can I just remove the old bolts from the stringer and screw new ones in? Or should I fill the holes with some sort of glue/sealant? This should be an interesting project because there's not much room to swing a wrench.

Thank,
Aaron

[GordMay]

Presuming (?) that those stringers are glassed wood, and that they're not compromised, & the flex mount fastenings are “lag screws” (not bolts), I’d certainly backfill (epoxy) & re-drill the holes.

Even better, would be to drill in (horizontally) from side, and insert threaded steel rod (hole up). New BOLTS could then fasten (down) into new rod.

[delmarrey]

I use 1/2" X 3" wide steel plates drilled and taped for hex bolts in several positions side-to-side so the motor is easily adjusted. Then lag bolt the plates to the stringers.

I've had motors where one could not get a straight shot on the hold down lag bolts, so they were installed crooked causing all kinds of problems trying to realign the motor.

Pictures later this eve..............

[Chief Engineer]

I sometimes drill and fill....post pictures if you can.

Thee are a number of different filling options

[s/v Jedi]

Originally Posted by Chief Engineer

I sometimes drill and fill....

You mean fill and drill, right? ;-) sorry, too many hours, not enough sleep here...

I am interested in how to fill them though... also what filler to use, but I assume high density. I was thinking of drilling oversize, using the dremel drumsander to sand a profile a bit down the hole so that the epoxy plug becomes locked in. But I am worried about the fastener (in direct translated Dutch we call them "wood-thread bolts" because they have a hex-head but threads like a wood screw if you can still follow me ;-)
The worry is that the threads break the epoxy instead of cutting into it. So, I was even thinking about using course-threaded bolts and tapping the epoxy!

I just (finally) got my mounts in too. Couldn't bring up the guts to take them into the engine room to check if they are the right ones but they look identical at least...

ciao!
Nick.

[delmarrey]

Originally Posted by s/v Jedi

I am interested in how to fill them though... also what filler to use, but I assume high density.

What I like to do is drill out the old lag threads left in the wood (in my case 3/8" hole for 5/16" lags) and then use hard wood dowels and epoxy to fill the hole. Smooth off, then put a couple more layers of glass over the top of the old, covering the dowels.

Pictures are worth a thousand words.............. and what ever you do don't use SS lag bolts. W/O oxygen they erode and soon they are not holding anymore. They only have to get wet from the wood.

[johnar]

depending on how tall the stringers are you can cut a slot down mid way for a backing plate inbedded with glass then another plate on top of the stringers, I do not see any way to make it stronger.


Dutch

[Chief Engineer]

Delmarrey's got it

Drill out existing hole...fill with dowel....then drill a pilot hole......not too small though

[s/v Jedi]

Hmmm... the only dowels here are poplar... is that good enough??

I was thinking, if I remove the lag bolts and all looks good (wood strong and undamaged), I could vacuum them for cleaning, heat them with heat gun and brush epoxy with small brush to impregnate the wood which should also swell a little. I'll just see and if I have faith I'll try it.

cheers,
Nick.

[James S]

Nick
I thought Jedi was aluminum...I just assumed your stringer or engine bed would have been the same.

[never monday]

put some life caulk on the lag bolts and screw her back down

[Blue Stocking]

Wrapping the lag screws with 2 or 3 layers of Teflon plumbers tape will allow you to back them out of cured high-density epoxy filler in oversized holes. Done it many times, including my own boat.

[S/V Antares]

James has a point. lf the stringers are alu. than they are likely drilled and tapped (Threaded ) or through bolted. Please post some pictures.

[delmarrey]

Originally Posted by s/v Jedi

Hmmm... the only dowels here are poplar... is that good enough??

I was thinking, if I remove the lag bolts and all looks good (wood strong and undamaged), I could vacuum them for cleaning, heat them with heat gun and brush epoxy with small brush to impregnate the wood which should also swell a little. I'll just see and if I have faith I'll try it.

cheers,
Nick.

Have you tried a hardwood store or hobby shop.

BTW epoxy shrinks when it cures. But if your using the same holes it would be stronger just lube the lag bolts with a wax when installing.

Originally Posted by James S

Nick
I thought Jedi was aluminum...I just assumed your stringer or engine bed would have been the same.

I would think a motor sitting straight on metal mounts would vibrate through the hull.

[James S]

I figured he would still use the isolating motor mounts between the engine and the stringers.