engine mounts

212rowboat

repowering from 4.3 to SBC... 

is there an adapter plate such as there is w/ auto's, or, am I looking at a drill and fill situation? 

212rowboat

roger- thanks Al. 

I was hoping that there was either a biscuit that mounted between the engine and the mount, or a plate that adapted to the boats blocks, that pushed it those four inches forward... Or, I was also hoping that the forward bolt/lag could become the trailing bolt/lag on the 'new' mounts... 

I'll tap new holes for the mounts- and fill the ones vacated... 

what is best to fill those with?  5200?  Epoxy?  

Michael T

When I swapped my perfectly good 4.3LX (100 hours) in my Rinker 190 for a Mercruiser 350 Mag we did NOT fill with caulking. We thought that would leave the area too soft. We were worried that the new aft lag would be too close to the old front lag hole and did not want the increased HP's torque to twist or in any compromise the stringers - as going from 190 HP to 300 HP was quite a jump. Later we went to 390 HP so it was good that we did it right.

We used a proper filler. I'll see if I have the brand name in my notes but I know for sure it was a non-shrinking, 2 part epoxy filler that was watertight. Then the holes were lightly sanded, epoxy primed and I used the white Interlux bilge coat as a final coat. I put three on. That was in 1994. The stringer area that we filled-in is still perfect today, not even a hair line crack, chip or bubble and those stringers have supported that 390 HP torque monster for over 15 years. Yes, I am ocd but it was such an easy thing to get right as I just sat in the open engine bay and did it right.

212rowboat

that's what I figured, MT, but I don't want to use something that could be done better- which is why I asked.  

the pedestals off the stringers are plenty wide, tall, and long enough- but I'm thinking it won't be a bad idea to add some material to them on the back and on the inside area- making them a couple inches more bulked, and w/ fiberglass over thin panel board and filled w/ epoxy that overlaps (pegs) into the vacated holes, but w/o adding more height to the area where the new mounts will lag to... 

it will be a nice, clean, repainted and replumbed engine room before the new motor is (permanently) mounted... I guess I'll have to hang the new engine in place aligned to the drive to know for absolute certain where the new mounts will go- unless someone has a stencil for such a swap? 

Michael T

@212, that's what we did. We hung it in place with a 1/16 plastic shim under the mount so it did not cut the stringer as we slid it in. We lined it up, pencilled the holes, drilled for lags, then installed the lags with Sikaflex , wiped-off the excess Sikaflex,and adjusted the height using a Mercruiser alignment tool. It will be a breeze for someone of your capability. Later when I had the 350 stroked to 383 we didn't change anything regarding the mounts as we did such a good job of installing the mounts that we felt they were solid. looking back they were and the time spent paid-off. Pictures of your project would be cool for all to see IMO.

Michael T

Very interesting. I had planned to do that with the 190. I called Rinker first and spoke with Kim Slocum and he advised that I use a 2 stage epoxy as the stringers in my 190 were fiberglass composites and he did not want wood dowel fillers. I had said I was going to use oak dowels. maybe mahogany would have been okay? Anyway, I used two part epoxy and those stringers have had that torque monster 390HP 383 on them without a gel coat crack so .......

Michael T

That explains using the dowel in the 212, in that case I would too!

Michael T

Makes sense.