Loose engine mounts

[carl190]

I discovered a small oil leak from apparently the rear seal during one of my last sails. Upon pulling the boat I noted that the prop had slid about 3/16 to 1/4 inch to the stern out of the cutlass bearing. This also shows on an intermediate bearing between the engine and the cut less beating. Examining the set screw on the prop collar shows the prop has not slipped in the collar.

What I then noticed was all four of the engine mounting bolts were loose to the extent that I could move the lock washers by hand. It appears the engine became loose and slid back. Tightening one of the bolts indicated that it would tighten adequately. The bolts are 3/8 brass with lock washers and lock nuts.

When I loosened the prop collar the line up with the engine was spot on! My current plan is to take off the output collar and examine the oil seal and key way because of the oil leak. After addressing what I find I am thinking about just retightening the engine mounting bolts where they are.
I am wondering if any one else has run into a similar problem, the boat is a 1976 tartan 30 with the original atomic four. I first thought the shims may have worked their way into the fiberglass bed or the underside of the bolts became loose somehow. I am now thinking the nuts vibrated loose.
I am a first time forum user and will greatly appreciate any advise or experience. I briefly search and didn't find any similar posts if there are a reference will be great. Thanks carl

[Al Schober]

The holes in the flange of the oil pan are considerably larger than the size of the studs. This gives the opportunity for the engine to move horizontally (as you've found out). This can have an adverse affect on the measured shaft alignment, keeping in mind that the horizontal alignment is just as important as the vertical alignment.
What I like to do is fill the gaps between the oil pan and the studs to prevent horizontal motion. The first washer under the oil pan must be big enough to cover the bottom of the hole. Then I just mix up some Bondo and push it in around the stud. Another washer and the nut on each stud finishes things up.

[carl190]

Al thxs, are you aware of torque recommendation for mount nuts. Also, do you know if the mounting bolts are glassed in. I am still amazed that all four nuts, with lock nuts, could come loose. I was wondering if the reason my nuts lessened was because of the bolts becoming loose from beneath.

[Al Schober]

On my boat, the studs are lag screws on the bottom end, going through the fiberglass into wooden timbers. In my case, the stud under the water pump had gotten punky - I had to reset it in epoxy (after letting it dry out a bit.
Some builders cross-drill through the timbers in line with the studs, then put lock nuts on the bottom end.
As to torque, depends on stud size and material. For a guide, the 3/8" head and manifold studs are steel and take 35 ft-lb. But more important is that they be secure. I recall one overnight race when I was catching a nap on a settee and the boat broached under spinnaker. I ended up with the engine cover on top of me. Just glad it wasn't a battery or the engine itself!

[romantic comedy]

On my Tartan 34 the engine is mounted with lag studs. They are brass and screwed in the wooden engine beds. The top is a stud with 2 brass nuts holding the engine.

A while ago I had to insert dowel pieces in the bed holes, then reinstall the lag studs because they had loosened over time.

It is not a strong way to have it, but has worked for 40 years so far. The engine is shimmed between the engine and the beds for alignment.

[carl190]

Thanks for the info on the lag screws I think that is probably what I have as well in the 1976 tartan 30. As a side note I did have to replace the glassed in wood under the mast step previously.

[Al Schober]

Well, mast steps are not really Atomic 4 topics. But, diversions are usually welcome. I think the members of this forum have addressed issues from washing machines to dog houses (canine). It's amazing the expertise that is on this BB...

[BadaBing]

My 1974 T30 also developed sloppy engine bolts. In my case it was the lag portion which had, over years, violated the wood threads it pieces.
The lags were so loose that my engine was basically held in place by gravity.

This past fall when I began my in place upper end overhaul I addressed the lags as well.
First removed the lags.
Drilled out the old lag holes until I found good hard dry wood.
By moving the drill around I drilled out a cone shaped hole in the mounting rails so that the small end of the cone shaped hole was pointed up.
I vacuumed out as much dust as possible
Mixed up home west system g flex epoxy and filled each hole about half way. Using a clean long screw I mucked the export in each hole around to mix in any remaining dust with the epoxy.
I had already threaded on the nuts to about where I wanted them on the cleaned lag studs and carefully taped off above where unwanted epoxy to grab. A little breeze in the nut bolt threads to prevent an accidental gluing of the nut to the bolt.
Then I filled the holed the rest of the way and simply slid the old but we'll cleaned lags into the now wet filled epoxy cone pockets.(after all my drilling they were at least 3-4" deep and 1" do a at the base, a bit more for and aft where the wood allowed)
The washers and tape held everything in place for the epoxy to dry.
After a couple days I removed the nuts and tape and hand tightened things us. Then I gave the epoxy a week,(I don't know if this is needed or not) to gain more strength.
Then I realigned the shaft and engine lamentable the nuts home.
The west system g flex is stronger than the wood.