A Question for you auto sparkies.

Submitted: Saturday, Mar 29, 2008 at 19:16
ThreadID: 56049 Views:1933 Replies:6 FollowUps:1
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I have a Mariner magnum 40 horse Out board motor with electric start.

Would this motor be able to charge a 55 amp hour battery while started and power a old Engel fridge and I mean old 20 years.

The idea is to use the fridge in the boat, and use the battery to start the boat and power the fridge, could the motor charge the battery at a better rate that the fridge would use?

Cheers Steve
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Reply By: Notso - Saturday, Mar 29, 2008 at 19:26

Saturday, Mar 29, 2008 at 19:26
Hook up an amp meter and see how many amps it's whacking into the battery.
AnswerID: 295458

Reply By: furph - Saturday, Mar 29, 2008 at 19:41

Saturday, Mar 29, 2008 at 19:41
Steve.
I had a 70hp. Evinrude on the last boat. Reckoned on doing something similar to your idea, but sadly the alternator/diodes setup only catered for about 4 amps to the battery.
I think this is because the starting of the motor actually takes so little from the battery that a voltage unregulated 4a. recharge is consideres more than adequate. (which it is)
Would love to find a small enough alternator to fit in the space available though... from a motorbike possibly?
furph
AnswerID: 295460

Follow Up By: TD100 - Saturday, Mar 29, 2008 at 19:46

Saturday, Mar 29, 2008 at 19:46
i dont even think they have that,more than likely a magneto that can barely put enough back in the battery to start it let alone run anything else.cheers Paul
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FollowupID: 561484

Reply By: Derek from Affordable Batteries & Radiators - Saturday, Mar 29, 2008 at 23:05

Saturday, Mar 29, 2008 at 23:05
I would not risk it.

Rather take a 2nd battery just for the fridge. The specs on the motor say 11 amps but that would be max at max revs and a willing battery.

Specifications:Propshaft Rated Horsepower 40hp (29.8kw)
Max RPM at Full Throttle: 4500-5500
Cylinders/Configurations: 3
Displacement: 42.5 cu in (697cc)
Bore & Stroke: 2.68" x 2.52" (68 mm x 64 mm)
Cooling System: Water-cooled, with thermostat & pressure-controlled
Ignition System: Modular CDI
Starting: Manual or Electric
Gear Ratio: 2.00:1
Gear Shift: F-N-R
Steering: Remote or Tiller
Alternator System: 11 amp (130 watt)
Trim Positions: 3
Exhaust System: Through prop
Lubrication System: Single point variable ratio
Fuel Induction System: Loop-charged (1 carb)
Operator Warning System: Overheat, low oil level
Shaft Length: Short 15" (381mm) Long 20" (508 mm)
Weight: 152lb (69kg)
Counter Rotation: N/A
Fuel Tank: Separate 6.6 US gal (25 litres)
Propeller Option: See dealer
Prop Selection (Pitch): 8"-19"
Propeller Drive: Splined rubber hub
Oil Injection: Std on electric N/A on manual
Carb Star Rating: N/A
SmartCraft Capabilities: N/A



AnswerID: 295503

Reply By: Steve from Top End Explorer Tours - Sunday, Mar 30, 2008 at 11:54

Sunday, Mar 30, 2008 at 11:54
Thanks for the info, I thought as much.

Cheers Steve.
AnswerID: 295561

Reply By: Member - Mike DID - Sunday, Mar 30, 2008 at 19:59

Sunday, Mar 30, 2008 at 19:59
One HP can provide about 500 watts of charging.

A 12 volt 150 amp alternator puts out 1800 watts (using about 4 HP)

So this motor would have adequate power to drive a Car Alternator - provdid you had the right gearing.
AnswerID: 295658

Reply By: autosparky - Tuesday, Apr 01, 2008 at 23:30

Tuesday, Apr 01, 2008 at 23:30
no there is only going to be 1/2 amp to charge battery
AnswerID: 296068

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