Mk II fuel tank capacity

[Mick Laver]

This is kind of a strange question, but can anyone verify the C34 Mk II's fuel tank holds 25 gallons? Given the inflated published figures for the holding tank and aft water tank I thought I'd ask. It seems like a pretty critical thing to know. Thanks.

[Jim Hardesty]

I don't know exactly.  I've never drained and refilled.  Its close to that.  That's the number I use.
Jim

[kwaltersmi]

I just replaced the fuel tank on my MkI this summer with a tank from Ezell (Catalina's supplier).  The tank is stamped 25 gallons, but I couldn't get more than 23 in when I filled it for the first time.  I believe Ezell told me this is the same tank as they supplied for the MkII.

[Stu Jackson]

I find no reason to distrust the information in the manual.  It could well be that the total tank capacity is rated at full measurement of the volume, whereas in real life one can only fill it up to where the vent starts spilling, since the vent connection may be from the side of the tank near the top.

The basic question, in my mind, is this:  What's the difference?

Why?  Because I always calculate my fuel consumption, never rely on the fuel gauge, and always work with ONLY 20 gallons of usable fuel anyway.  On my boat, I use 0.5 gph, refill very 20 hours with 10 gallons or 40 hours with 20 gallons.  Forty hours at 5 knots gives me plenty of range (200 nm).

The Mark II boats with larger engine have higher fuel consumption, reported often on this board.

[Mick Laver]

Trust ... but verify. :)

The question arises from one of those "unforeseen circumstances" where it would have been really useful to know there was as much left in the tank as I thought. I don't rely on the gauge either, and since we consistently use .75-.80 gph,  knowing our total hours I can pretty accurately predict how much it'll take to fill up. That said, I've never taken more than 20 gallons. Do I really have 5 to go in a pinch?

[Jim Hardesty]

Sort of a side... does any one else experience this question.  How full do you fill the tank?  The last time I filled the diesel filled it with no over flow.  Motored out of our harbor, in and out of another harbor, 1 1/2 or 2 hours.  Then sailed hard on the wind and got some over flow out the vent, may be a quart or so.  Not the first time I've experienced this.  Do you think that my diesel vent is correct?
Jim

[Ron Hill]

Guys : When I pulled my MK 1 fuel tank (way back when?) I found that it had a data plate that said it was a 25 gal tank!!
All of the MK 1 literature talked about 24 gal tank!!  Mine was the OEM aluminum tank.

My advice to the MK II (doubting) owners is to pull the aft cabin port side panel and use a mirror to look for the data plate on the tank or
pull the tank out and look at the data plate on the top!!

I believe (but can NOT confirm) that the two versions of the C34 have the same tank!!

A thought 

[kwaltersmi]

I believe (but can NOT confirm) that the two versions of the C34 have the same tank!!

According to the current tank manufacturer (Ezell), the tanks are the MkI and MkII tanks have the same dimensions, but the vent and ground plate, bolt tabs and aluminum thickness have changed.

[Roc]

My Mk II has a plastic tank.

[Ron Hill]

Guys : The - plastic tank was an option (over the metal tank) - for awhile in the late 1990s. 

Catalina discarded that option because owners complained about diesel smell (I was told). 

A thought

[Jack Hutteball]

Jim,

When we purchased our MK ll, #1555, when sailing with a full tank I would get fuel out of the vent when the boat was heeled to port.  I found that the vent hose was routed barely higher than the tank, so was lower than the fuel in a full tank when on a heel.  Replaced the line with a longer one and ran it as high as I could.  That eliminated the problem.  I think some vent lines may have been installed too short to get them high enough.

Jack