Engine Bolts and Stringers

Greetings.

Our engine (Westerbeke 82hp upgraded years ago from the original Volvo 62hp) is secured to the boat by 12 or more bolts. These engine bolts drill into a Stringer. The engine bolts at the most forward-port aspect of the engine have lost the ability to tighten. Subsequently, they rattle loose with vibration and will pop out (see pic). While new to big boats, even I could work out this was not good.

The stringer appears to be a foam core surrounded by fiberglass. The securing power of the bolts appear limited to where they pass through the fiberglass frame. My plan is to re-drill new holes to re-site these bolts, thus resecuring the engine.

I would appreciate any other comments or thoughts on this matter. Anyone else had this problem? (Have you checked your engine bolts lately?) Do I need to lift the whole engine out at this time and do something with the stringers? Why are the core of stringers foam? Any information is helpful.

Cheers,

Milo

s/v The Last of the Normal People

Swan 47/048

Dear Milo,
I had the same problem and had the engine basment completely re-built, between the GRP a steel plate has been positioned and drilled, in order to get new screw throught it, look at the pic below
Matteo (38/067 Only You)

look at the final basement

Milo,
I don&prime t think that the stringers under the engine are made of foam enclosed in GRP, that would be an almost useless structure.
The stringers can be made of hard wood but, more probably, of steel or s/s. I am expecting Lars to tell us.
What Matteo did is the optimal thing to do but, if you do not want to embark in an expensive job, there are other possibilities depending on the material of the stringers.
1) steel or s/s: re-tap and use larger bolts.
2) wood: clean the rot if present and glue with epoxy filler some proper threaded insert. You may easily find any kind of insert you like on the net.

One thing one has to be aware of is that s/s bolts into s/s threads tend to freeze if forced.

Regards
Daniel

Dear all

Engine beds have steel inserts inside under the GRP top, but the steel flat bar length and location is usually adapted for the original engine. If another engine with longer distance between the supports is installed some bolts may go outside the steel insert area. The recommendation is then to cut a slot enabling a piece of flat bar to be put in and secured, and repair the slot.

Ordinary steel is used for the inserts.

Lars

Dear Gentlemen:

Thank you for your helpful advice. At some point I imagine doing something similar to Matteo, but for now have gone with the temporary solution of upsizing from 3/8 to 1/2 inch lag bolts. In all, 6 of the front 8 were replaced and felt firm going in. I will monitor closely and at the first sign of loosening I will take the next step.

Thanks.

Milo

Milo

The GRP in the engine seating top is fairly thick, and threaded bolts should hold quite well, but vibration tends to loosen them. With lag bolts it is suggested that the predrilled holes be rather tight, and epoxy used to secure the bolts.

Kind regards

Lars