Battery hook up

Just got a 9.9merc electric start yr. 2000. I want to hook it up with two batteries and a 4way switch (On, Off, Batt 1, Batt 2) Suggestions......Thanks RC

Re: Battery hook up

I can't see any issues with doing that as long as you use the switch appropriately. I know guys out there are sayin' yah yah yah, but I don't recommend leaving the batteries in parallel while not charging.<br /> I'd recommend:<br />-batteries in parallel while running<br />-batteries disconnected from motor and each other when engine off<br />-boat accessories connected to b2 (if you kill b2 with your microwave, satellite sterio, sexlites, you can still start with b1)<br />-install circuit-breaker and switch between b2 and accessories.<br />Try to attain a matched set of batteries. <br />I don't care what charging/ign. system you have, but.....refrain from switching batteries 'Off' when engine running. Good luck and good sailing!!<br />

Re: Battery hook up

Hmmm. Okay, RC, I can dig OFF, B1 and B2. Is ON going to be BOTH?<br /><br />I agree with Schematic's advice except that I would put about a 40 Amp diode between B1 and B2 so that your start battery cannot supply accessory current but can share charge current with B2 and the accessories.<br /><br />Red sky at night. . .<br />JB

Re: Battery hook up

I guess it would depend on the switch he has in mind. Using only one diode for isolation has its draw backs.(whole other story).<br /><br /> If both batteries are connected together in the 'on' position, both will get charged. If the switch is opened when engine off, accessories will draw off b2 only. Pretty subjective to the switch he has. We'd need to know more....but this is what I interpreted it as.<br />If we want an easy optimal system, I'd recommend he toss the 4-way, put one disconnect to engine, a continuos-duty solenoid between the two batteries (controlled by accessory position in key switch and a small momentary push button switch for emergency starts from b2.) Batteries will be separated during cranking, together when running, separated with engine off. <br />A last possibility that could be done would use two diodes, no solenoid, no accessory interface needed. This would require an engine harness modification. I'd only advise this if he has an electrical background.<br />RC, I'd be happy to draw you up a schematic(diagram) if you so desire.<br /> Snowed 2" today....so cold....can't feel my fingers.....you guys are too lucky!!<br />

Re: Battery hook up

Thanks for the imput on the Batt hookup. Have limited accessories so maybe B1 to engine, B2 to access. Positive to switch, neg to each other. I think this will give me the option to us B2 to start if needed. Thanks RC

Re: Battery hook up

Please excuse my ignorance, but does the 9.9 hp also have the option to pull start if required? If so, why worry about 2 batteries?

Re: Battery hook up

Ditto....grandx!! Rc, I believe you said in other postings it was a sailboat. Why on earth would you want 2 batteries if you have limited accessories? I pictured a martini in both hands, women in bikini's all around, music blairing, fridge, stove, sat. TV, vibrating bed, cell phone etc....LOL . Thats where these suggestions apply. If you have limited acc., use one battery, one disconnect, and in the event the battery goes dead(rare in your case) pull your rope!!....LOL<br />

Re: Battery hook up

Schematic, most excellent advice on the set up with a momentary microswitch and a solenoid, my buddy has this set up on his diesel alumaweld 22, great for for starting when 1 batt is low just hit the microswitch and presto I like it I like it

Re: Battery hook up

you could use a battery isolater whitch will charge 2 bat seperatly from one alt/gen<br />it will only charge the bat that needs it automaticly.<br /><br />i use one on my 4 X 4 for runing a winch or charging my travel trailer bat seprate of the truck with the truck alt.<br /><br />no harm done<br />louis

Re: Battery hook up

you got it mrnobody, a battery isolator is "two diodes" (easy to build)<br />-thanks MURX