Starting Battery options

[NiceBeny]

My new to me boat might be in need of a new starting battery? even when fully charged (?) it turns over slowly and the engine has a hard time starting, I had to switch on the house deep cycle battery with the parallel switch, then it turned over fast and started right up. any thoughts on make, amps, etc? it has a 43 horsepower volvo penta turbo with dual alternators and water maker pump attached. I have had the boat 2.5 years and don't know how old the batteries are? the house batteries are AGM deep cycle.

 

[Benny17441]

It does sound like the starter battery is weak but to rule out other possibilities I would have the battery tested. Take it to any automotive parts retailer and they will usually perform a computerized load test for free. While you are there you might as well look at the marine starter batteries they may have on the shelf. I'm not a battery enthusiast so for me the cheapest group 24 wet cell starter battery with at least 650 Cold Cranking Amps would do it. ( a larger battery is always better but not necessarily required if the engine starts right up) On the other hand I would put my money on the house bank and you have a good one. Also check the charging system for your starter battery.

 

[stevemitchell]

I decided to do away with a dedicated start battery and have a much larger house multipurpose bank. However, I have a much smaller boat than you, and my engine doesn't require as many cranking amps. Having the battery tested is a good first start as suggested by Benny 17441.

 

[Philip_Oceanis 361]

I would say, for a starter battery any cheap, appropriate size (around 80amp probably?) car battery would do. Obviously this does not apply for house batteries.

 

[seadaddler]

I would agree with most already advised and no need to get too big,I just added a new
start battery which I use to start my 29 HP Yanmar & Gen and have 4-6-volt in my House
bank,I went to sam's or local auto store but can't remember what size but nothing crazy.
Nick

 

[woodster]

wally world has ever start batts that are made by east penn

 

[Bill Roosa]

Couple other things to check:
the starter battery terminals and or the 3 way switch may be loose or corroded. If you check the owners manual for the motor it should list the kilowatt rating for the starter motor. amps @12 volts = xxx kW*1000/12. My 50 HP yanmar has a 1.2 kw starter and so draws 1.2*1000/12=100 amps

 

[Benny17441]

It is no secret that a starter motor if ran continuously would burn up and that it could quickly deplete a battery but the start period of a healthy engine is approximately 2-3 seconds which allows the starter and battery to recover between uses. The average starter will consume around 5 ah in those 2-3 seconds.

 

[Ralph Johnstone]

The average starter will consume around 5 ah in those 2-3 seconds.

Actually ........... it's even less than that:

(3 sec/3600sec) X 120A starter motor = 0.1 ah

I have GOT to get out sailing .

 

[Stu Jackson]

Either the battery or the ground wire from the start battery (which has two ends: at the battery and at the engine). Easier to check the wiring first.

 

[NiceBeny]

thank you everyone, since I don't know how old the battery is and they are cheap (compared to most things on a boat) I am going to replace it and cross that off the list.

 

[sailnewbie]

If it helps I have a 18 HP and use a small lawn mower battery and it's more than enough, so the smallest car battery would get it done easily unless there's starting issues