TradewindSailor
Well-Known Member
I have twin Yanmar 3ym30's with SD20 saildrives.
My partner throttled back hard and there was a nasty noise from the starboard engine. When I dived in to inspect the prop, I discovered that it had gouged out a chunk of hull :-( My immediate suspicion was that the saildrive mount was damaged or had gone soft.
I pushed and pulled with the starboard engine, and compared it's movement with the port unit. There was definitely more play in the starboard side one ..... but I had to be sure. I rigged up a block and tackle and lifted the engine at the saildrive end enough to put the mount in tension. Using a mirror and a torch it was quite plain that the engine mount rubber had parted partially from the steel body.
The bolt studs are welded onto the steel body. The top steel plate is aligned with the engine mount with a pin ... so the plate won't turn when tightening the nut. The bottom plate is probably the same.
In my case the thread above the top nut is badly corroded and prevents the nut from being totally removed. I could of course cut the excess thread off ... but I didn't fancy the steel sawings messing up the engine and the space. So I removed the rear mount from the engine .... no problem.
It wasn't too difficult to separate the rubber from the steel frame using a chisel. The joint was already 2/3rds separated. One face had been separated for some time as there was a good deal of rust on the plate faces. It surprised me how cleanly I managed to remove the rubber. There were only two small areas of rubber left adhering to the plates and the rubber faces were in very good condition, showing that the rubber does not adhere strongly to the steel.
It was going to be a pain to remove the bottom of the mount as I had no room to swing the large spanner. So I thought I'd repair it.
I tested various glues on the non-mating face of the rubber. Superglue was useless. Araldite worked well, and so did West Epoxy thickened a little with colloidal silica ...... both couldn't be removed from the rubber without damaging the rubber.
The repair : I prepared the steel faces with an 80 grit grinding disk and sanded the mating surfaces of the rubber with 80 grit as well. I cleaned the faces down with isopropinol alchohol (meths is fine), applied the glue, weighted the joint enough to hold it all in place and squeeze a little of the glue out. I allowed the epoxy 24 hrs to cure before running the engine.
The repair tests out well and may be better than original. It has been in service for about 20 running hours.
I chose repair because of the difficulty of removing the bottom plate and the good condition of the rubber. The $200+ for a replacement mount didn't help either.
What does concerns me ...... are the standard Yanmar engine mounts up to the task? They have to be strong enough to support the engine inverted in heavy sea conditions ..... otherwise a capsized yacht might have to contend with a loose engine and a gaping hole where the saildrive used to be!
My partner throttled back hard and there was a nasty noise from the starboard engine. When I dived in to inspect the prop, I discovered that it had gouged out a chunk of hull :-( My immediate suspicion was that the saildrive mount was damaged or had gone soft.
I pushed and pulled with the starboard engine, and compared it's movement with the port unit. There was definitely more play in the starboard side one ..... but I had to be sure. I rigged up a block and tackle and lifted the engine at the saildrive end enough to put the mount in tension. Using a mirror and a torch it was quite plain that the engine mount rubber had parted partially from the steel body.
The bolt studs are welded onto the steel body. The top steel plate is aligned with the engine mount with a pin ... so the plate won't turn when tightening the nut. The bottom plate is probably the same.
In my case the thread above the top nut is badly corroded and prevents the nut from being totally removed. I could of course cut the excess thread off ... but I didn't fancy the steel sawings messing up the engine and the space. So I removed the rear mount from the engine .... no problem.
It wasn't too difficult to separate the rubber from the steel frame using a chisel. The joint was already 2/3rds separated. One face had been separated for some time as there was a good deal of rust on the plate faces. It surprised me how cleanly I managed to remove the rubber. There were only two small areas of rubber left adhering to the plates and the rubber faces were in very good condition, showing that the rubber does not adhere strongly to the steel.
It was going to be a pain to remove the bottom of the mount as I had no room to swing the large spanner. So I thought I'd repair it.
I tested various glues on the non-mating face of the rubber. Superglue was useless. Araldite worked well, and so did West Epoxy thickened a little with colloidal silica ...... both couldn't be removed from the rubber without damaging the rubber.
The repair : I prepared the steel faces with an 80 grit grinding disk and sanded the mating surfaces of the rubber with 80 grit as well. I cleaned the faces down with isopropinol alchohol (meths is fine), applied the glue, weighted the joint enough to hold it all in place and squeeze a little of the glue out. I allowed the epoxy 24 hrs to cure before running the engine.
The repair tests out well and may be better than original. It has been in service for about 20 running hours.
I chose repair because of the difficulty of removing the bottom plate and the good condition of the rubber. The $200+ for a replacement mount didn't help either.
What does concerns me ...... are the standard Yanmar engine mounts up to the task? They have to be strong enough to support the engine inverted in heavy sea conditions ..... otherwise a capsized yacht might have to contend with a loose engine and a gaping hole where the saildrive used to be!
