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Tiara Open Need to replace 6 Gel Batteries. (3 house & 3 engine) - 38 Open w/450 Cummin's
I'm getting ready to change all 6 GEL batteries as they are 18 years old and serviced me well. Never had an issue starting but this year when starting for the first time after winter layup I needed to bring all 6, via the parallel switch, to start.... In any case I looked to see what size they are but was unsuccessful. Know they are either group 27 or 31.... Anyone know which ones were used or can I use the group 27's to save approx $500.00.. CCA is lower (550 vs 505) as well as reserve power (190 vs 160). the size difference is small.... Suggestions greatly appreciated
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I like to overshoot when it comes to batteries just in case (or more like when) I do something stupid and need to lean on the starters for a while. But I think the group 27's will work for the engine bank. Cummins 450 6cta specs call for 1560 MCA, 1250 CCA for cold start and a minimum 480 minute reserve (assuming 12V system). If you spend a lot of time at anchor and or invert off the house bank that might suggest the group 31's or larger. M2C

Btw that pretty amazing to have any battery last that long, let alone batteries that spend their life turning over diesels.
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Thanks for the rapid and informative response... Yea I was happy with the performance and longevity of the original GEL batteries... Was concerned over the last few years but never had an issue starting even after being on anchor overnight (w/o running generator).... Boat is in the water 12 mo/yr with chargers on all the time. Wanted to replace with same brand, think they are Excide/Sonnenschein, but can't find a source... Looking at Deka Gel....
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I replaced my five gels after 15 seasons last year.  Model 31's were the original equipment in a 35 Open with 8.1L gas.  I believe East Penn Mfg (Deka) makes most/all private brands of marine gel batteries.  I went with the NAPA brand as they (NAPA) were offering 20% off if you were a AAA member.  It was worth me joining AAA for the discount.
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Rcwiegand thanks for the suggestion. Called our local NAPA parts store and 6 new Deka 8G31DTM Gel batteries will be ready for pickup tomorrow... Price was significantly lower than I found on-line... After 18 years the boat deserves new batteries..... Will see the difference I'm sure.. Thanks for the suggestion
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Hi Capt

I just put these on my boat !!
So far all great

[Only registered and activated users can see links Click here to register]

Sent from my iPhone using Tapatalk
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Those batteries look great. Was considering AGM as a replacement for GEL batteries but was concerned regarding the difference in Charging profiles. Especially the float levels. Looked into changing the chargers profile but decided to purchase Deks 8G31DTM GEL's. Additionally, I had great sucess w/GEL's in that they were 18 years old and still giving reasonable performance. Hopefully the news one will be as good... M2C
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Need to replace 6 Gel Batteries. (3 house & 3 engine) - 38 Open w/450 Cummin's00