1969 Chris Craft Roamer 46 Refit: Engine Beds

My priorities for 2014 are 1) propulsion install, 2) steering, and 3) windows, glass and sealing up all exterior openings. On one of the frosty cold Saturdays in January, I went to the boatyard and started measuring the engines and the space they’ll occupy in the engine room. Lemme tell ya–when it’s 18°F outside, the engine room of an unheated aluminum boat is the last place you want to be for very long. Fortunately, it didn’t take long to get the measurements. Before frostbite set in, I had everything I needed and charged back home to play with google SketchUp on the computer.

Your basic virtual Cummins 430 Diamond in a Chris Craft Roamer 46

Your basic virtual Cummins 430 Diamond in a Chris Craft Roamer 46

The vertical stringers are 1/4″ aluminum plate that’s seam welded on both sides to the hull plating. The stringer plates are topped with 2-1/2″ x 3″ x 1/4″ 6061 aluminum angle that is seam welded on both sides to the stringer. The width from the top outside edge of the angle on one side to the other is 28 inches.

Motor mounts land right on top of the OE stringers

Motor mounts land right on top of the OE stringers

And when I say “right on top”… I mean dead-center over the 1/4” aluminum vertical stringer.

Vibration isolator bolts will have nowhere to go

The isolator bolt is 1 inch diameter. If I set it all the way inboard (relative to the engine), the bolts that attach the isolators to the stringer will go directly into the vertical stringer plate, leaving no way to put nuts on them. If I move the isolator outboard, the bolts will go into the angle. If I continue moving the isolator outboard, the bolts eventually hang over the air with only about 1/3 of the isolator perched on the stringer.

I could remove the motor mounts from the engines and have the slots cut further inboard. But if I do that, I’m reducing the width of the footprint. On the principle that the mounts that came with the engines were engineered with a certain size of slot, I decided to maximize the width of the isolators. Which means I have to make new engine beds outboard of the existing stringers.

I'm thinking something like this

I’m thinking something like this

5″ x 3″ x 3/8″ 6061 angle with 3/16″ gussets and a 1/4″ bar running along the bottom so the offset matches the OE angle that’s welded to the outside of the vertical stringer.

I like the orbit feature of SketchUp that allows you to view the object from any angle and capture it in a jpg file…and free is a very good price!

While I kind of felt like January and February 2014 were lost months on the refit, it’s not a bad thing to have the time to think through and design stuff like this. I was able to do the same thing during the paperwork SNAFU lull, when I worked out many of the interior concepts for the boat. With the engine bed designs done, I ordered the materials from Posners. By the time the nasty winter weather broke I was ready to start fabricating.

Dry fitting all of the pieces

Dry fitting all of the pieces

I used my Harbor Freight handheld bandsaw to cut the 25′ stick of angle into four pieces and my Shopsmith bandsaw to cut the gussets. Then I used the 12″ sanding disk attachment to square up all of the parts and leave a nice finish.

Not a bad fit

I will hold off on welding it all together until I’ve got the prop shafts in so I’ll know where the engines will sit. This is one of several welding operations that will happen one day in the next few weeks.

Next up on our 1969 Chris Craft Roamer 46 Refit: Return of the Bow Seat Windows


6 comments on “1969 Chris Craft Roamer 46 Refit: Engine Beds

  1. Marty Molloy says:

    The Canadians will be pleased to see that you are using yellow gussets. ;0)

  2. John Longwell says:

    What CAD software is this?


  3. Mark Young says:

    I actually used autocad, after i gridded off the hull of our 41 roamer and than once all stringers were located as well as the overhead decking obstacles were plotted we inserted the autocad files for the Cat engines as well as the autocad drawing of the Twin Disc Trans. Having the OEM suply the drawings allowed us to figure out where the problems were early on and accomodate for the challenges. Once we did a dry run onto our temp engine mounts we could see that we were within 1/4″ of the proper location for all to fit and it was relatively easy to make the final adjustment. So if you can get the drawings and they will work in your software it may well be worth the effort! Good Luck,

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