Rebuild engine stringer mounts

[rockin411]

I’m pulling my old Yanmar out to replace rings and sleeve and now is the time to fix my rotten mounts. I haven’t found a lot of information on how people have rebuilt them. I’ve seen wood, L brackets, and composite material used. Does anyone have a strong opinion or reference I could look at?

[capt jgw]

WEST System epoxy has a nice write up on it in thier downloadable manual.
https://www.westsystem.com/wp-conten...anual-2015.pdf

[Rumrace]

Systems west is a good idea but the Yanmar if oiled wears pretty even. Rebuilding the upper end with big end bearings is risky. As to stringers most boats have some wood tossed in. It’s a mistake. Trapping most metals in glass big mistake
I’ve restored 2 Donzi hulls. Same model 20 years apart donzi only had wood in the transom. Was a plug of 1” plywood. It had a Ford Evibrude cutout was delaminating so the transom is now cut out for mercury and it’s nylon epoxy transom. “Ribs” are a few glasses in walls and engine mounts are glass blocks glassed into the boat. Because we had decayed engine mounts for a 460 Ford to a GM LS3. If it was a GM 454 we were replacing same problem. We made an aluminum anodized frame to hold the LS3 and two batteries. The frame bolts onto helicoils into the side of the old mounts. This allowed us to lower the engine mount remote filters. The battery mounts bolt on to the glassed in wall behind the rear seat. The rear rails of the engine chassis bolts to studs on the new transom and support to water jacket throughhull headers. Donzi still makes the 18 and come from the factory with LS-3 Mercury. They are in metal motor mounts I’m not sure where or how.
Plastic in a raw form can and will absorb water. The plastics I use go to a dryer the day before use. Nylon is awful but new versions of nylon are astounding.
They are composite but not laminated but infused with carbon fibre. Once cast and cured it’s truly waterproof unlike polyester.
You may find you mounts are shot but no damage to stingers.

[SohoSail]

Originally Posted by rockin411

I’m pulling my old Yanmar out to replace rings and sleeve and now is the time to fix my rotten mounts. I haven’t found a lot of information on how people have rebuilt them. I’ve seen wood, L brackets, and composite material used. Does anyone have a strong opinion or reference I could look at?

I had the yard rebuild mine for my 4JH3 when some other engine work was being done. I would have to dig out the pictures, but they glassed in mahogany ( I think ) to build up the new mounts. They did a beautiful job. As I indicated, I forget the details in terms of number of layers of cloth over the wood, but it sure beat the glassed in steel ones it replaced. PM me if interested in pictures and more info.

[wingssail]

Our new engine mount stringers (needed during replacement of Westerbeke to Yanmar) were laminated in place fiberglass over fir timbers. The fiberglass build up was approximately 3/8 inch thick. The mounts were lag bolted into the wood. That was 30 years and 6600 engine hours ago.

[skipperpete]

I do a lot of engine alignments and one of the biggest problems is the lag bolts into an encapsulated timber core that has rotted.... or sometimes the lagbolts have stripped the threads after many years of service so , lacking a Shipwright service and not really wanting to lift out the engine, I’ve had good results by boring vertically into the hold down bolt holes with a hole saw, sometimes just an inch in diameter, sometimes 3” (depending on the condition of the core) and putting in a timber plug with epoxy, glassing over the top and redrilling the hole. This is a really quick fix, do the boring and epoxy job one day and the alignment the next ....but if the entire core is rotten there is no choice other than lifting the engine, cutting the cap off the bed and recore ing the whole bed.