Engine Mount - Sheared Lag Bolt - Inside Stringer Photos

racushman

O34 - Los Angeles
So this weekend I began the process of cleaning up my M25XP for painting.

In the process I discover the forward/starboard engine mount has lag bolt that first appeared loose, and on further inspection is sheared off. It’s hard to get a good view, however the threads will not engage at all and I suspect the bolt sheared off cleanly at the engine bed level. I’ll attach pictures from my iphone as an update to this post.

Anybody deal with this before? it’s the aft bolt, so really hard to get a good angle to drill it out. Any ideas what would cause this to happen?

Thanks,
Rob
 
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bigd14

Sustaining Member
Blogs Author
Bummer, that sounds like a tough area. The lag bolts can loosen up over time, especially if they are repeatedly loosened and tightened up to align the engine. Maybe it worked loose and allowed the motor to vibrate and shear stress the bolt? Maine Sail has a good write up about using an automotive jack to lift the engine up enough to replace the mounts. That might be enough to access the broken lag bolt. Might be a good time to replace all the mounts too. Several of the lag bolts on my boat were loose when I bought it. When I replaced the motor mounts I used hanger bolts (combination wood and standard threads) epoxied in place so I could adjust the engine by loosening the nuts and preserve the integrity of the lag bolt section in the engine stringer. Good luck and keep us posted on progress.

EDIT: I wonder if a right angle or flexible drill bit attachment and a short bit would get you there?

 

racushman

O34 - Los Angeles
I had the same wonder/idea about the flexible drill bit attachment. I’ve never tried one before.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
I would guess that you can disconnect the shaft-coupler bolts (be sure to hold the shaft in place if you have a PSS seal), and then raise the engine. I have met a mechanic that was using a small scissors jack scavenged from an old Civic. I have heard of using a basketball and inflating it with a small compressor, but have no first hand experience.
I used to put some torque on the mount bolts on our original M25XP about every other year. Just 'cause. One or two of 'em would have loosened up just a little over time, too.
Really hard to get a closed end wrench or a short socket on those rear bolt heads. Some therapeutic cursing will be involved. :(
Plan B is to lift the engine up and move it forward to really get at this stuff. Having done all that when I replaced ours with a Betamarine, that involved disconnecting a lot of parts and wiring.
 

JSM

Member III
Had a similar situation my our 34-2 a few years ago. I found that after changing the original motor mounts some of the lag screws would not tighten , they just wanted to spin in their holes. My engine was also mounted on three mounts and the fiberglass that the front mount screwed into was striped as well making it impossible to keep the engine aligned with the shaft.
I welded nuts to the bottom of some 1/8" steel plate and drilled out the old holes in the engine bearers to accomodate the nuts. The steel plates were then laged into the bearers. The motor mounts are now held in place with machine bolts. NO MORE STRIPED HOLES.
For the front mounts I fabricated new bearers out of 3" square steel tubing and angle iron which was drilled and tapped to accept machine bolts for the mounts.
Luckily I just had to disconnect the exhaust hose and the fuel line and lift the eng(ine with a cheap chain hoist from Harbor Freight which was hung from a beam across the companion way. The chain hoist will give you almlost infinite verticle control of the engine and was able to get the job done in an afternoon by myself.
(Front center mount in pic has since been removed)
 

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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Just one more thing.... about a decade ago I replaced our original '88 motor mounts with new ones. Upon careful inspection, I found that one of the rear mounts had the rubber soften so much that it was down to metal on metal. This is a 'wear part' that needs to have a xxx number of hours replacement plan, IMHO. Maybe 1200 hours or a bit more.... kind of like scheduling a valve adjustment or a shop test for the injectors.
 
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Kenneth K

Contributing Partner
Blogs Author
I'm still waiting for someone to drill or cut into the side of one of those engine stringers and run an endoscope in there to see what's inside.
  • If you knew it was hollow, then you could cut large sections of it open, build vertical wooden "bulkheads" and fill them with epoxy suitable for re-drilling.
  • If you knew that at least parts of them were solid inside, you could figure out what sections could be lagged into what sections can't.
But, since no one seems to know what the inside of an Ericson engine stringer looks like, we all struggle with how to repair those loose lag bolts.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
The factory hose run for the raw water intake on the O-34, has the sea cock under the galley sink. Then the hose went thru a drilled hole in the end part of the nearest hat stringer, under the teak/hollly sole section, and then under the starb. side of the engine compartment face. They routed it into the engine bay thru a drilled hole in the bed log inside face, forward part near the RW pump on the engine.
I long ago re-routed the intake back under the aft berth and added a Groco strainer -- the routing from there up the starb. side of the engine is shorter with few turns.
Now, back to the question... I have poked a finger into that hole in the frp bed log, and my best guess is that the wood inside is (duh) laid up against the top where the mount lag-bolts/screws are torqued down into it. What with the thickness of the frp section and the added wood, the large screws hold well. Still, as noted, they will loosen up over time. Lots of vibration in a small diesel, is my surmise.
Referring the pix in my engine-changeout blog on this site, the new aluminum riser bars were secured with "machine threaded" bolts into new holes in the fiberglass and into what, from inspection of the sawdust, was oak. (Our engine installer complimented EY on using good material.)

Back to the present and the need to get new lags to hold, my best guess is that the old hole will need to be expanded and filled with thickened epoxy and then threaded for a bolt. Easy to do with the engine move out of the way, but... oh my. More work. Having moved our old Universal out onto the cabin sole, it is quite a bit of work (at least for an amateur like me).

**DO... place a fitted piece of 'masonite' over that sole section before putting tools and dunnage and possibly an engine on it. I did, and the expensive sole section was unharmed.

Not trying be a sunshiny Pollyanna kind of person, but having most sailing/cruising shut down or limited for this summer, does provide an opportunity for a lot us to complete long-contemplated boat projects and upgrades. FWIW, restoring the soundproofing and all of the hose and wiring inside the engine compartment was Hugely Rewarding for me. The Admiral was noticeably impressed-- she likes tidy and reliable things on the boat. :)

Keep those pix and narratives coming. As Red Greeen used to say on his marvelous show: "Keep you stick on the ice, and we're all pulling for ya."
:D
 

bigd14

Sustaining Member
Blogs Author
Almost been there. From what I could tell there is a piece of softwood lumber a a few inches thick that runs the length of the stringer. There seems to be some airspace between the bottom of the lumber and the hull. Whether the thickness of the lumber varies along the stringer length is uncertain. I did not do any exploratory drilling to verify this. Rather, I had a bunch of neat epoxy rapidly disappear down the hole I was trying to bed the hangar bolt into which led me to this conclusion. I then poked a skinny wire down there and found it would hit the hull. I had to use thickened epoxy to bed the bolt. Also the forward mount definitely had airspace under the wood, I could see and verify this with a flashlight.

Edit: As per Loren's simultaneous post, I would have expected hardwood, but the material that came out when I drilled across the hat section to place the bed extensions to support the new mounts looked (and drilled) more like Doug fir. Maybe they used what they had on hand?
 
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JSM

Member III
Stringer construction is definetly wood. I drilled eight pilot holes in mine to lag in the steel plates for my rear mounts. All of the shavings that the drill bit produced were wood. Driving the lag bolts for the plates required a lot of force ( lip balm to the rescue !) leading me to think that they are solid wood. The problem with lag bolts is that they are nothing more than big wood screws and wood doesn't hold the threads that the lag bolts cut very well. One or two trips in and out of the hole and the threads that the lag cut in the wood are softened up and easily stripped.
I learned this the hard way when I replaced my mounts four years ago and discovered that some of the lag bolts would not tighten up "hard". After a lot of "vibration frustration" due to engine alignment not holding I went with the operation I posted above.
Now all motor mounts are held in place with machine bolts going into metal threads and can be loosened and tightened repeatly without self destructng . Neither I nor anyone who ends up with this boat after me will ever have to deal with this BS problem again.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
So the mid-80s factory procedure was: insert wood "backing plates" into the molded TAFG engine stringers to provide grip for engine-mount lag screws.

That sound right?
 

JSM

Member III
Sounds right to me. Length and thickness of the wood "backing plates" is anyone's guess.
 

Alan Gomes

Sustaining Member
Perhaps these photos will help. My boat is an E26-2, but I'd guess the construction is the same for the stringers as on the larger Ericsons. The port aft-most lag bolt stripped out the wood and so my friend Neil (who posts here as Parrothead) welded up a plate with nut and we inserted it through the aft end of the stringer. There is definitely wood laminated to the underside of the stringer where the lag bolt penetrates and the stringer is indeed hollow. (The Atomic 4 in the photos is not my engine but the spare one in Neil's garage, where he welded up the plate.)

Since that was the only one that stripped out we decided to do a small plate to address just that one bolt. But if others were to follow suit and strip out, the complete repair would be insert a plate that runs the full length of the stringer and which we would use for all of the holes. This was a quick repair that is doing the job for now.
 

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Alan Gomes

Sustaining Member
Perhaps these photos will help. My boat is an E26-2, but I'd guess the construction is the same for the stringers as on the larger Ericsons. The port aft-most lag bolt stripped out the wood and so my friend Neil (who posts here as Parrothead) welded up a plate with nut and we inserted it through the aft end of the stringer. There is definitely wood laminated to the underside of the stringer where the lag bolt penetrates and the stringer is indeed hollow. (The Atomic 4 in the photos is not my engine but the spare one in Neil's garage, where he welded up the plate.)

Since that was the only one that stripped out we decided to do a small plate to address just that one bolt. But if others were to follow suit and strip out, the complete repair would be insert a plate that runs the full length of the stringer and which we would use for all of the holes. This was a quick repair that is doing the job for now.
Correction: It was the STARBOARD aft-most lagbolt.
 

Kenneth K

Contributing Partner
Blogs Author
Great! Best pics I've seen yet of the insides of a stringer. So it's a hollow, 3-walled box-beam. Doesn't really matter how thick the wood in the top and sides is--apparently somewhere between 1/2 - 3/4" thick. Once the hole is stripped, the lags aren't gonna re-set without some additional work being done.
 

lindaloo

Member II
I'm late to this thread but I'm wondering if Rob has made any progress.

The lag bolt in the picture looks stainless and snapped at the stringer surface. The motor mount will have to come out and the motor moved aside. I suspect it will be nigh on impossible to drill down the middle and try to use an easy out. Machine shops have techniques for engine block studs but they don't apply here especially since it is not machine thread.

JSM's idea to weld nuts to steel plate might be the answer and I'd do both nuts. That means some grinding so the plate lies flush with the stringer.

Of course an easy option is to abandon the broken stud and rotate the motor mount so the bolts are not in the fore-aft axis. Maybe 30 deg would be enough to get the new bolt holes 1" away from the old. Universal mounts appear to be NOT axial. I believe Yanmar mounts are stiffer longitudinally to handle propeller thrust and softer side to side. Not the case here.

Can the brains trust find fault with the easy option?

Rob
Vancouver, BC
E34
 

racushman

O34 - Los Angeles
I have not made any further progress on this issue, but do appreciate everyone's insights... especially the intelligence the the stringers are hollow.

At this point I think I have two primary options: 1) do as lindaloo suggests and see if a i can rotate the mount enough axially to get a new drillable spot (I think this is possible), or 2) drill out the existing and fit a slightly larger bolt.

I bought one of those flexible drill bit couplers, but with it in hand I am not very confident it's up to the job of drilling through metal and fiberglass.

All this said, I'm increasingly of the mind that at 31 years of age all the motor mounts should be replaced. Which then raises the question of whether i can really do that with the engine in place AND drill the new hole. OR maybe I should pull the engine and give it some TLC, all new hoses, impellers and paint. And now probably you all can understand why I've actually done nothing :)

Lastly, as I look at Alan's pictures of the hollow stringer it makes me wonder if a better long term solution would be to drill holes through the side of the stringer that would allow access to thru bolt new mounts instead of having the lag screws.
 

Alan Gomes

Sustaining Member
I have not made any further progress on this issue, but do appreciate everyone's insights... especially the intelligence the the stringers are hollow.

At this point I think I have two primary options: 1) do as lindaloo suggests and see if a i can rotate the mount enough axially to get a new drillable spot (I think this is possible), or 2) drill out the existing and fit a slightly larger bolt.

I bought one of those flexible drill bit couplers, but with it in hand I am not very confident it's up to the job of drilling through metal and fiberglass.

All this said, I'm increasingly of the mind that at 31 years of age all the motor mounts should be replaced. Which then raises the question of whether i can really do that with the engine in place AND drill the new hole. OR maybe I should pull the engine and give it some TLC, all new hoses, impellers and paint. And now probably you all can understand why I've actually done nothing :)

Lastly, as I look at Alan's pictures of the hollow stringer it makes me wonder if a better long term solution would be to drill holes through the side of the stringer that would allow access to thru bolt new mounts instead of having the lag screws.
Pulling the engine is not the worst job in the world. I've done my 1GM and it wasn't that bad. True, it's a much lighter engine than yours, but the same basic principles apply. Giving that engine some TLC, including a spiffy paint job, would be a good thing.

Re: the stringers: Would it be possible for you to drill a hole in the front and back end of the stringer and fit a metal plate that runs the length of the stringer? Then, once in place, you could drill through the stringer and tap the holes in the metal plate. Your existing holes from the lag bolts would serve as ready-made pilot holes. It seems to me that this would be the best fix. In my case, as I mentioned, we had only the aft-most bolt to address so we went the easy route rather than a plate running the full length of the stringer.

What do you (and others) think?
 
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