Motor Mount Fabrication-Long

[TJS]

Ok it has been a long time since I posted anything about my 190ES Baja project. I have had many other projects in line before getting back to this boat project. I had to make a flat bed dump bed for my 02 Ford F250 superduty (the original bed rotted, go figure). Had many house and yard projects along with having a daughter right after I bought this boat. So now the Wife is bugging me to get the boat done for next year. I will update my original post where I am at soon. Transom and stringers are out. Grinding still continues this weekend. I am almost ready for wood and glass work. Will be running a mercruiser 350 and alpha outdrive.

Anyway onto what I want to do with my motor mounts. The original stringer/motor mount was just a wider stringer for the last 40? or so of the stringer. The new stringers are marine plywood and stacked ?? (2) all the way and the last 40? they are 3 stacked ?? marine plywood. There will also be a bulkhead. I do not like the way the boat builders just put lag bolts into the motor mount pads and screw then right into the wood.

So my design will be sandwich plates out of 3/16? or ?? stainless plates the will take the shape of an upside-down ?|_|? which will be slipped over the wider stringer where the motor mount pad would be. It will have threaded stainless bungs welded where the motor mount pad bolts would reside. They will be threaded I think ?-13 or whatever fits. The bungs will be sunken into the milled out wood and waterproofed with PB or epoxy, most likely 1.5? or so deep. There will also be 4 cross through bolts. These will be waterproofed with PB in the holes and then re-drill the PB to the size of the through bolts. I know this is probably overkill but that is what I do. All my welds will be TIG welded. I have a Bridgeport Mill a lathe and many other fabrication tools. I will post them here when I am done. I know for sure these can also be used to fix existing spinning lag bolt mounts instead of trying to epoxy the lag bolt holes or using larger lag bolts. See pics or hand drawings. Sorry no CAD here.

 

[Bondo]

Re: Motor Mount Fabrication-Long

I know this is probably overkill but

Ayuh,.... Boat motors have been lag bolted in, since the 1st motor was bolted into a Boat,...

What's Wrong with the Proven method,..??

When ya hang the motor on the alignment bar to set the "Point" of where the motor mounts are goin',...
What happens if yer ssteel inserts don't line up,...

With lag bolts, ya hang the motor, align it, predrill the holes, 'n sink the lags,...

Yer system is gonna lessen yer adjustabilities,..

 

[TJS]

Re: Motor Mount Fabrication-Long

Ayuh,.... Boat motors have been lag bolted in, since the 1st motor was bolted into a Boat,...

What's Wrong with the Proven method,..??

When ya hang the motor on the alignment bar to set the "Point" of where the motor mounts are goin',...
What happens if yer ssteel inserts don't line up,...

With lag bolts, ya hang the motor, align it, predrill the holes, 'n sink the lags,...

Yer system is gonna lessen yer adjustabilities,..

Not sure why my Response post to Bondo was deleted.

My install process would be no different as you describe Bond-o, only difference is I will be using the plates with the bungs. The hang, alignment and hole marking process will be the same. Yes I am aware of lags being used forever but that to me will cause problems in the future. You don’t see automotive manufactures using lag bolts and there is just as much vibrations going on as well. I spoke to 3 local boat owners that have had to jerry rig their lag bolts, i.e. bigger bolts, 5200 etc which all required to pull the engine up. I even spoke to one about my plate idea and he said he would have done that if he knew I could make them for him. Not sure how I am going to lose adjustability as you state. I have used this plate process on my 750HP blown Big block chevy jet boat with no issues and H-bar alignment is critical as well.

 

[GWPSR]

Re: Motor Mount Fabrication-Long

You would lose lateral adjustment (port-starboard perpendicularity to the transom) unless your motor mounts featured slotted holes. The up-down alignment is not an issue, but you'd have trouble with the side to side adjustment.

I should add, I like your idea, if I could visualize a good way of achieving that adjustment.

 

[Bondo]

Re: Motor Mount Fabrication-Long

Not sure why my Response post to Bondo was deleted.

My install process would be no different as you describe Bond-o, only difference is I will be using the plates with the bungs. The hang, alignment and hole marking process will be the same. Yes I am aware of lags being used forever but that to me will cause problems in the future. You don’t see automotive manufactures using lag bolts and there is just as much vibrations going on as well. I spoke to 3 local boat owners that have had to jerry rig their lag bolts, i.e. bigger bolts, 5200 etc which all required to pull the engine up. I even spoke to one about my plate idea and he said he would have done that if he knew I could make them for him. Not sure how I am going to lose adjustability as you state. I have used this plate process on my 750HP blown Big block chevy jet boat with no issues and H-bar alignment is critical as well.

Ayuh,.... Nothin's been deleted in this thread, or I could see it,...

Maybe ya hit the wrong button, or the web ate it,...

I ain't sayin' there's anything wrong with yer plan, just agreein' with ya, that yer Wwaaayyyyy over engineerin' it,...
Notice the quote,...

I'm askin' What are the perceived benefits,..??

No matter what ya do, somewhere it's metal to wood,...

Motor mount blocks fabbed up with resin, 'n glass are pretty darn dense, 'n reasonably rot resistant, if treated fairly,...
Even with 3" lag bolts straight down the middle,...

 

[GWPSR]

Re: Motor Mount Fabrication-Long

One iBoater fabbed motor mounts that had a top portion that contained a through void so that the engine mount would use bolts and nuts instead of lags. I don't recall who that was, but there was some elegance in that design. If I recall, it wasn't just an upside-down U shape, but had more of a box-on-its-side design.

 

[TJS]

Re: Motor Mount Fabrication-Long

Guess I do not understand the lateral adjustment comment. The adjustment would come from the slots in the mercruiser engine mount. I looked at the mounts and the largest stud or bolt I can use to allow some adjustment will be 3/8”-16 (I may use fine thread though) which will be fine for this application. Remember I will not be welding the bungs underneath my boxing plates until I locate and align everything. Then I will locate the holes in the plate, remove the plate, machine the large holes for the bungs and then weld the bungs in. At the same time I locate the holes in the plate, I will locate the holes in the stringer wood for the bungs to set in. I can holder tolerances to .002” (two thou) or so which is good in my book. Also remember my hole drilling of the plates will be done on a Bridgeport milling machine with digital readout in which the vice is indicated within .001(one thou), resulting in near perfect hole alignment. I don’t see any issues with this. Yes I know it is over engineered but that is just me. I am doing this because I can. It will only add maybe 2 hours total more work to the rigging process.

 

[GWPSR]

Re: Motor Mount Fabrication-Long

Ah. I was envisioning holes and bungs first, engine and alignment after the fact. Your plan ought to work just fine. I also subscribe to the over-engineering club. Like jigngrub says: "I consider overkill a job well done... plus a little extra."