In my last article, I wrote about the second step in the process of installing the Cummins engines into my Roamer. I came up with one plan for engine beds that didn’t work out at all, then cut up one of the beds to make spacers that should work just fine. But then I realized that the top of the stringer on one side isn’t square to the stringer upright, which complicates things just a bit. Just when I thought I’d worked around that problem, another one jumped out to bite me.
I even had to remove the locknut (lower left corner of the picture above) to lower the front of the engine far enough.
But then, I checked the clearance under and around the engine…
There’s also zero clearance between the gear cooler and the top of the stringer. I need to move the engine out of the way and make some space.
The gantry is absolutely the best tool I’ve ever made. Moving these one-ton engines around by a couple thousandths or a couple of feet is a one-man job.
That little wedge I cut out of the aluminum frame to make room for the oil pan will come in very handy in my next article.
I need to cut the top of the stringer along the line I marked with a Sharpie so the fuel cooler bracket at the top of the pic above will fit between the stringers. These coolers are notorious for causing installation headaches, and I’m experiencing that personally on my boat. Either way, it’s nothing that a gantry and jigsaw can’t fix.
I’ll square that up the spacer when I finally install it in the next step.
I was so focused on the gear-to-prop shaft coupler gap, and centering the engine between the stringers, and trying to figure out what to do with the front motor mounts that are bottomed out, and the inner stringer that isn’t square to the upright frame that I totally missed the HUGE problem in the pic above.
The prop shaft coupler and gear coupler are perfectly mated, and the propeller is the exact distance it should be from the aft-most strut. But the 1/2″ bolt that will secure the rear vibration isolator to the stringer lands in the middle of the transverse frame behind the gear. That frame is welded to the engine-side of the upright stringer and the piece of aluminum angle in the pic above that forms the top of the stringer. There’s no good way to drill a hole through the stringer that won’t put the bolt and nut in the middle of that upright frame or the weld that holds everything together.
I can’t move the engine back so the bolts clear the frame, since that would require pushing the prop shaft further out of the boat, which would put the propeller hub 2″ past the aft-most cutlass bearing. I can’t pull the prop shaft further into the boat, because that would put the prop too close to the aft-most strut. The prop shaft can be shortened, but it’s already machined and installed. I could also have a new set of motor mounts made (which is probably what I should have done from the beginning). All of which reminds me of something I wrote about before: the butterfly effect, and how little tiny things that happened a long time ago can cause ripples in time that wind up kicking me in the balls years down the road.
I was originally going to order the prop shafts after the mechanic installed the engines, so I’d know exactly how long they needed to be. I fired the mechanic after he didn’t get the engines installed for several months back in 2012, but I’d already ordered the prop shafts based on his measurements. If only we had done things per the original plan…
While mulling over what to do about this new problem, I kept working on the spacers.
As I was finishing up sanding the spacers, an idea from years before came back to me. I remembered that in my original plan I was going to use DriveSavers to isolate my prop shafts from the gear. DriveSavers are basically industrial strength rubber donuts that isolate prop vibration, provide drivetrain protection in the event of a prop strike, and they break electrical continuity between the hull (via the engine & gear) and the prop shaft and prop, which is even more important on metal boats than on other hull materials. Far more important, though, was that DriveSavers generally require the engine to be moved forward or the prop shaft to be cut by about 1″ to make space for the rubber donut. In my case, they’ll permit me to move the engines forward far enough for those aft-most rear vibration isolator bolts to clear the upright frame, plus provide all of the benefits that originally convinced me they were something I needed on my boat.
We’re back in business…I think.