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MK 1 propane conversion

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MK 1 propane conversion

One of the upcoming projects we are planning is to convert from CNG to propane.  Where would the propane locker on a MK 1 be installed?  The CNG bottle lays horizontal under the portside aft seat.  This would be a great "out of the way" spot for propane, but I know it's not a safe arrangement for it.  Anyone have any ideas or pics of a MK 1 propane install?  I see lots of discussion for the MK 1.5s and Mk 2.


Dan & Amanda Reed
1989 Catalina 36 #947 Miss America
Fin Keel Std Rig
FL Panhandle

Channel Islander
Channel Islander's picture
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Joined: 10/8/11
Posts: 340

My 1984 has the propane locker installed in the aft locker, on a platform that keeps it out of the way of the steering gear. 

Nick Tonkin
Website Administrator, C36/375IA
C36 tr/fk #255, Santa Barbara, CA 

Last seen: 10 hours 2 min ago
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Posts: 21

Thanks, Nick.  I was going to measure when I get to the boat again to see if the Seaward rectangular locker will fit there under the "hump" in the aft locker seat.  I was hoping for a recessed locker, but doesn't look like many options for that.

Dan & Amanda Reed
1989 Catalina 36 #947 Miss America
Fin Keel Std Rig
FL Panhandle

LeslieTroyer's picture
Last seen: 19 hours 43 min ago
Joined: 3/13/16
Posts: 201

on my MK 1 it the propane hangs off the port stern.  Propane is heaver than air so sinks if released, CNG is lighter that air so rises - Propane needs additional safeguards to be safe.  There are ABYC and CG requirements that the propane locker must be 100% enclosed to the interior of the boat, and must have a vent line at the bottom that drains overboard.  Additionally the locker can not be dual purpose.  I was going to mount the tanks in the anchor locker (I don't like the way it looks on the stern) - but the dual purpose clause makes that not work.  There are also regs on the locker lid such that if there is a lid over the locker (like your lazerett lid) that lid can not physically close if the propane locker is still open.  There are commercial lockers that meetg these spec's but they are expensive.  I've seen some that hang off the stantions that look nice - 

The boat also did not have propane alarms in the bilge (on my to do list).  

Be safe and make sure you get it inspected afterwards.


Les & Trish Troyer
Everett, WA
1983 C-36 Hull #0094

bakerha's picture
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Joined: 7/23/10
Posts: 146

Dan and Amanda:
I made the conversion several years ago after CNG became impossible to get in the Mid-West (and expensive if you could find it).  New stove with oven also as I could not find the orifice's to convert our old one.
I installed the box in the aft lazerette as in the picture and I'm sure it does not meet all the legal requirements but I tried!
The box is made out of 1/2" ply - sealed and painted. It is vented Top and bottom, contains the regulator, solenoid, and space to store my small bottles used for my grill. It also has an lpg sensor inside so I would know if there is a problem with the connections or the bottles. I mounted an lpg sensor in the bilge near the stove as well.  So far so good.  I used a Fireboy S-2A control system mounted aft of the refrig on the aft galley bulkhead. The Admiral loves the stove and oven!
As you can see I had to trim the rudder flange about 1/2" to get the box in, but have had no ill effects from that.
Box external dimensions are 16 wide,13/ 1/4" depth, 16 3/8" high. The bottom flanges out so it could be bolted directly to the shelf. I'm not sure how consistent our boats are, so I would highly recommend careful measurement before you go to far. My first attempt at a box was about 1/2" to big and no matter what I tried (bfh)- It would not fit.
Hope this helps
I'm trying to find time to do a full Tech article for the site - will let you know if I get that done.

Harold Baker
S/V Lucky Duck
Sandusky Ohio, Great Lakes
1989 C-36 mkI TR/WK M25XP

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That construction looks slick, Harold!  You say that it's vented top and bottom, but of course the bottom one is the one that counts in case of a leak.  Does the bottom vent go to a tube an through-hull out the stern?  Did you have room for a tank solenoid valve inside your box?  I'm guessing with those dimensions, you use a 10-pound propane tank.

John Parsons
1999 Catalina 36 Mk II - Hull 1771
Tall Rig, Fin Keel
Bay City, MI, USA

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