Moderated Discussion Areas
  ContinuousWave: Small Boat Electrical
  Battery Rigging for Mercury OptiMax

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   Battery Rigging for Mercury OptiMax
sciguy20 posted 05-09-2009 04:22 PM ET (US)   Profile for sciguy20   Send Email to sciguy20  
I have a [1999 Mercury 150-HP OptiMax motor] on a 22-footer I just bought. The battery setup has a battery switch (OFF-1-BOTH-2) and two batteries, both newer deep-cycle 600-CCA or 750-MCA batteries. I have read that this motor requires [a battery with a rating of a] minimum 800-CCA or 1000-MCA. I have to think about how and if I need to change this set-up.

I can hook in a new starter battery as Battery-1 and leave one deep-cycle with all electronics directly hooked to it as Battery-2. I'm not sure about having all the house appliances (GPS receiver, fish finder, and aerators) hooked into one battery. There's a three-bank charger on board for the two separate trolling motor batteries, and I guess one bank charges both deep cycles in the back.

Is it bad for either the engine or the batteries to have it rigged as is, which is about 1,200-CCA or 1,400-MCA when the battery switch is on "BOTH" (which I assume means they are in parallel)? The engine starts well, so it's not a prolonged large load on the batteries during starts. Is this a bad situation as rigged?

Any advice on this?

jimh posted 05-09-2009 05:57 PM ET (US)     Profile for jimh  Send Email to jimh     
If you now have two batteries, each with a rating of 750-MCA, and if you connect them in parallel (by putting your battery switch in the BOTH position), then you will create a combined battery with a rating of 1,500-MCA. This combined battery will have sufficient rating to meet the demand of the Mercury OptiMax 150-HP motor, which requires a battery with a minimum rating of 1,000-MCA.

There is no particular harm done in this approach. The only limitation of this approach is that neither battery alone has a rating sufficient to start the Mercury OptiMax motor, or their ability to start the motor may be very marginal.

The reason for having two batteries on a boat is to provide redundancy. In your configuration there is not complete redundancy, as you will need both batteries on-line to meet the starting requirements of your motor.

jimh posted 05-09-2009 06:06 PM ET (US)     Profile for jimh  Send Email to jimh     
The primary purpose of the battery on your boat is to provide for engine starting. If your engine cannot be started without a battery, then it is reasonable to provide redundancy in the battery. I assess your current situation as follows:

Can the motor be started without a battery? In the case of the Mercury OptiMax, the answer is no. The motor requires a battery to start, and it also requires a battery to run. A battery is absolutely essential for a Mercury OptiMax motor.

Because a battery is absolutely essential, I would then propose that there be some redundancy in the battery. A battery is not a 100-percent reliable device, and it is reasonable to expect that there may be a situation in which a back up battery is needed or would be extremely valuable.

If neither of your two batteries is capable of reliably starting the engine by themselves, then you should think of them as a single battery. In this view, you boat does not have dual batteries. It has a single battery which is distributed between two separate cases. Essentially, you are operating the boat with one battery.

My recommendation is to replace at least one or both of the engine starting batteries with a new battery that has a rating of at least 1,000-MCA.

Please read your owner's manual for the Mercury OptiMax motor and pay careful attention to the recommendation for the battery. It has been reliably reported here that the manual contains explicit prohibitions against use of a deep-cycle battery for engine starting.

sciguy20 posted 05-10-2009 12:58 PM ET (US)     Profile for sciguy20  Send Email to sciguy20     
thanks Jim-- I appreciate the response. i understand the redundancy issue, but I only have room for two batteries, and i need a deep cycle for the electronics. I suspect that if i just replaced one with a dedicated starter battery (in the "1" position) and just used the other deep cycle for electronics, in a situation where the starter battery was low I could switch to "all" and get her started to get back home.
I should note that i never go off shore-- mostly lakes and if salt it's limited to inshore....not interested in going offshore with 22 ft of fiberglass.


Bill K

Liteamorn posted 05-10-2009 03:30 PM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I have an Optimax engine and I run 2 starting batteries each capable of starting my motor on its own. Today's electronics do not draw that much power to demand a deep cycle battery. I stay off of the vhf radio and have installed LED deck lights which draw almost nothing. I run one battery at a time and alternate which one I use so as to keep them both charged. Unless you use an electric trolling motor or some other high-current accessory I would opt for redundancy.
sciguy20 posted 05-10-2009 06:37 PM ET (US)     Profile for sciguy20  Send Email to sciguy20     
Thanks-- I'll have to think about that; in addition to the GPS and fish finder, I also run the live wells off the one battery, so I fear I'll be draining a starter while on the water with all that going on. I think the best option would be two starters and the one deep cycle, but not sure where to put the third one!
jimh posted 05-10-2009 07:56 PM ET (US)     Profile for jimh  Send Email to jimh     
As long as your engine is running there is no worry about battery load. When your engine is not running, there should not be any load on the starter battery. Move pumps for live wells to another circuit, not the starter battery.
bluewaterpirate posted 05-10-2009 08:11 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I have a 225 Optimx that requires 1000 mca. I use two AGM batteries (start/house) connected to an BEP 716 Battery Management Cluster. The BEP uses an ACR that manages the charging of the batteries. After starting the BEP isolates the start battery to the alterator. When the voltage reaches 13.7 volts the VSR opens letting the alternator charge both the start and house battery. If at anytime the start battery drops below 12.8 volts then the VSR disconnects the house battery from the charging circuit targeting the start battery.

In my configuration I run two chartplotters, two VHF radios, fishfinder, a stereo, and two AC outlets. I've been running this configuration for three years plus and I never drained either battery.

Here are some pictures: 4892322_2160096_31023479_WebSmall_3/ Image-4892322-31023479-2-WebSmall_0_969e28a3a3fc24c5e560a295e48fdceb_1 4892322_2160096_31023618_WebSmall_3/ Image-4892322-31023618-2-WebSmall_0_0b0b6d9d699443e506c7495a4448c888_1 Image-4892322-31023627-2-Web_0_e50186a015c3402e87b38e5063b44781_1 Image-4892322-31023587-2-Web_0_d81727d574f4fe1514b427bce277a994_1 Image-4892322-31023594-2-Web_0_fb84c1b956a3156707b1dc2bdb359d81_1 Image-4892322-31023558-2-Web_0_6d0e7d149d62184e5c0740fd65aa9328_1 Image-4892322-31023608-2-Web_0_85a69c63a8a2c5d110657a3d1b21cf6e_1 Image-4892322-31023604-2-Web_0_fe763d0d1f5d3e09608a79a0da77468e_1 Image-4892322-31023602-2-Web_0_1801ee477bc3d7ae4f4f5484a4e70b41_1 Image-4892322-31027468-2-Web_0_5b196225909de12597cd5da2d704a415_1

The boat is a 210 Ventura. Image-4892322-31032154-2-Web_0_893ff1e787e78482089e6fe2b7338d30_1

I did all the rigging myself's very straight forward and easy to do. Took me two days to complete.


Liteamorn posted 05-11-2009 08:31 AM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I have a live well also. My 2005 150 Optimax has a pretty healthy charging system (60 amp). In 2 years I have never had a problem. I will not let the batteries get to old.
I used to run the deep cycle/ starter type batteries in all my boats and I worried about killing my battries with the starter batteries that came with my Eastport,to date I have not had that problem.
sciguy20 posted 05-11-2009 04:36 PM ET (US)     Profile for sciguy20  Send Email to sciguy20     
Tom-- that's an exceptional e-rigging job; I'll have that as a future goal (as well as having any compartment on my boat look so clean!). Seems like a perfect set-up for both re-charging and redundancy.
Thanks for the tips and advice, everyone; see you out on the pond!


Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.