C34MkII fuel tank maintenance

Ron Hill · December 24, 2019, 02:49:02 PM

Guys : Jim is saying that on a MKII the aft cabin panels are interlocked just the opposite of the MKI (starbd first and then aft).
On the MKI there are two lengths of panel screws. Just make sure that you don't use the longer screws for the aft panel or you might screw a hole in the aft water tank!!

Just use a "heads-up" when taking things apart and note differences!!

A few thoughts

Breakin Away · December 30, 2019, 09:08:55 PM

Quote from: Ron Hill on December 24, 2019, 02:49:02 PM
Guys : Jim is saying that on a MKII the aft cabin panels are interlocked just the opposite of the MKI (starbd first and then aft).
On the MKI there are two lengths of panel screws. Just make sure that you don't use the longer screws for the aft panel or you might screw a hole in the aft water tank!!

Just use a "heads-up" when taking things apart and note differences!!

On the subject of noting differences, the panel on my MkII are not like Jim's. The side panel overlaps the aft panel slightly. It's close enough that it looks like it could go either way depending on the order you put in the panels, and/or how precisely the panels are aligned. (i.e., if one panel is allowed to "sag" a bit before the screws are tightened, then it sticks out a little and may lock the other one in)

I have not actually removed my side panel yet, but that's what I saw when I went back there:

Breakin Away · January 11, 2020, 04:30:11 PM

I finally made it down to the boat today and succeeded at removing the side panel (3 screws along the bottom), so it's time for an update to point out a significant difference in my boat vs. the others mentioned here:

I HAVE A PLASTIC FUEL TANK. I assume that Catalina switched over to this at some point, because I can't imagine why the tank would have been changed out. Does anyone else have this? If so, is it before or after my MkII #1535? Please let me know what you have.

Note the pictures. There is NO WAY I can get to the gauge cover to remove it from the aft berth - I'd have to remove the covering wood(?) in the cockpit locker to get to the top of the fuel tank. It's just too tight a fit (see picture). So I can't use the fuel pump that I purchased to drain the tank like Jim Hardesty suggested (but he's got #1570, so did Catalina switch back to the older design?). Instead of pumping, I pulled the hose off the Racor inlet port and gravity-drained it into a jerry can. I got about 5.5 gallon out of it, which is exactly what my fuel gauge said I should have based on the prior calibration that I posted last year. Since that calibration assumed the rated capacity of 25 gal, pretty much confirms that my actual capacity is 25 gal with this apparently different tank.

Also, comparing my picture to the ones posted by Dave Spencer and Jon W, it's clear that my tank is mounted higher above the floor (greater head pressure so boat can run without lift pump?), and the overall enclosure is shorter because it does not extend the entire length of the aft berth - the enclosure stops about a foot short of the forward wall of the berthing area. This tank is a much tighter fit both vertically and horizontally, which eliminates good access from the aft berth. I can't even see how I could remove it if I wanted to, because the mounting brackets are blocked by hoses and other stuff.

Breakin Away · January 11, 2020, 07:09:42 PM

This Catalina Direct listing seems to explain the history:

QuoteIt is reported by Catalina that this aluminum fuel tank was installed at the factory beginning 2/5/2004. But it is also reported that it replaces earlier plastic fuel tank and even earlier aluminum fuel tanks if the tank was installed aft, to port of the aft berth.

https://www.catalinadirect.com/shop-by-boat/catalina-34/engine/fuel-tank-25-gallonc-34-c-36/

I'll have to measure the tank dimensions for comparison with my opening, but it seems my fuel tank nook has much less vertical clearance (floor much higher) than the one that Dave Spencer showed. Looking a Jon W's new tank, I doubt I could make that one fit because of the fill port on top. But it looks like CD has their tank with the fill port on the aft end, which might fit. I don't need to replace my tank, but nevertheless it's interesting to see these differences between the different boats.

Here are some pictures for comparison:

Mine

Dave Spencer

Jon W

Catalina Direct's current tank offering

Jim Hardesty · January 12, 2020, 06:54:03 AM

Breakin,
On Shamrock there are 2 deck plates accessed from cockpit locker, one for the fuel shutoff one for the fuel gage sender.

https://www.westmarine.com/deck-plates

If you don't have them, it may be good to install them.
Sorry that this project isn't going easy.
Jim

Jon W · January 12, 2020, 09:32:59 AM

You can barely see the underside of the two deck plates Jim is talking about at the top of the photo of my tank you posted above.

Ron Hill · January 12, 2020, 09:58:58 AM

Guys : In the late 1990s Catalina had 2 replacement fuel tanks for the C34 - aluminum and plastic.
It is my understanding that they discontinued the plastic tank. Owners complained that their plastic tanks had become permeated with diesel and the smell of diesel was overpowering.

A thought

Dave Spencer · January 12, 2020, 11:10:44 AM

Breakin,
As others have stated, I too have an access plate in the port side locker to get to the fuel shut-off valve. But just one, not 2 like Jim Hardesty has on Shamrock.

Looking closely at the pictures you posted comparing my tank, Jon W's and yours, it's clear that Catalina made some change to the design of the port side wall sometime between my boat (#1279, 1994, Mk 1.5) and your boat (#1535, Mk II). You can see the tank is much higher. The lip supporting the "teak" sidewall looks to be in the same place but the tank floor looks to be at least 150mm (6") higher and the forward wall in your fuel tank compartment looks to be 200-300mm farther aft than the lip on my tank and Jon W's making your fuel compartment much smaller although the tank is reported to be more or less the same capacity. Also, the tank appears to be 100mm or so farther aft than mine and Jon W's.

Do you know what is under your fuel tank? Surely the effort to redesign the area and create a cavity under the tank had to be for some good purpose. I doubt that it was to allow fuel to flow without a lift pump... mine does that without difficulty. (There are lots of discussions about the purpose of the lift pump and its interconnection with the oil pressure switch in previous posts.) Also, it looks like you have a solid wall along the forward side of your fuel compartment. Do you know what is forward of that wall? I don't have a wall and my fuel tank is open to the plumbing, and water muffler accessible through the cabinet under the sink in the head. If my arm was long enough, I could reach the fuel shut-off valve from the head. That area always struck me as wasted space so perhaps some good use was found for it in the Mk II boats.

Sorry I'm not much help but it's interesting to see some of the differences in the C34 across the production run. Many of us are aware of key differences between Mk1, Mk 1.25, Mk 1.5 and Mk II boats but I haven't seen anyone point out this difference before.

Good luck with your project... it sounds like it will be a challenge. Maybe a phone call to Gerry Douglas or another long term employee at Catalina is in order.

Noah · January 12, 2020, 11:36:06 AM

Breakin—Don't take Jon W.'s tank as "standard", especially for your MkII. He has a 1987 MkI (different than MkII) and he had his tank custom made with size adjusted, the fill hose fitting moved to the top of tank and two tank inspection ports added.

Jon W · January 12, 2020, 03:08:27 PM

FWIW - in addition to adding 2 access plates and relocating the fill port, material thickness was increased and I added a flange to the aft end of the tank for a screw to secure that end of the tank to the wood support.

Breakin Away · January 16, 2020, 08:10:35 PM

Hi all, sorry about the delay responding. For some reason, I didn't get email notification of the responses.

The "project" is pretty much complete. My only reason for trying to get into the top of the tank was to pump out the ~5 gallons of leftover fuel for inspection and storage over the winter in a verified clean jerry can. Given the difficulty getting access, I drained it through the hose by gravity/siphon. The fuel looks real clean, so I don't feel any need to remove or open up the tank.

A few responses to your comments:

Fortunately, I have no diesel odor (even after pulling out the wood panel) or other sign of permeation of the tank. No need to replace it. The panel will go back on after I bring a vacuum down to suck way any dust around the tank.

I am also curious what is under and forward of the smaller "cabinet" for my tank. There must have been some reason they made this design change, but until I can dig around again back there, I don't know what's behind the fiberglass.

I do have two deck plates in the port cockpit locker, both located at the forward end of the locker. I've used the fuel shut off valve several times (though more recently I use a pinch tool to shut off the fuel closer to my Racor pump when changing the filter). The second inspection port probably covers the fuel gauge sender, though as I recall it is not well centered on the opening. If I ever wanted to get it out, I would probably have to unscrew the tank and shim it a bit to get the sender centered. I do not recall seeing a third port further aft, like Jon W shows in his picture.

In the springtime, I am probably going to pump some fuel though the rubber hose into the tank through the dip tube. Doing this at a high rate of speed may loosen any stuff that may have coated the hose. Then I'll pump it back out again and inspect to see what's there. Rinse and repeat. But so far, everything looks pretty clean except for a little solid residue in my Racor filter (which is why I'm inspecting my fuel so carefully).