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1981 Merc 470 Starter Amperage?

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big_chief

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What amperage should the starter test? Motor is 1981 Merc 470 (Grady White).

I brought the starter to the auto store and the reading was showing only 75 amps... Sometimes, the starter would not turn over, unless hit with a mallet... but nothing past 75-80 amps.

BACKGROUND:

Ran fine for about a year... then sat about 2-3 months. The boat is weak turning over. I tested battery(s), charged, etc... and they seem fine. Also had them bench tested at the auto store. 910 cranking amps on one... 625 cranking on the other.

Gave it afew cranks and it would barely get the motor turned over. Then it stopped trying to start completely. I hit the starter afew times with a mallet and it tried again to turn over... So I assume its the starter.

I pulled the starter out of the boat and gave it 12 volts... it makes a "clunking" sound when starting compared to a "wing-wing" sound that I am used to... Sometimes it wont even engage, unless you hit it.

Model: Arco 50143... Sells for $225.00 on the net... Anyone know where to get one cheaper?

Thanks,
 
Re: Merc 470 Starter Amperage?

big_chief said:
I brought the starter to the auto store and the reading was showing only 75 amps...
Click to expand...

on the engine or on the bench?

on the engine, with the throttle wide open, I would say that is low, and an indication of a bad connection or low compression

on the bench, I'd say that's a bit high

if you have to hit anything with a hammer to make it work, you don't want it out on the lake
 
Re: Merc 470 Starter Amperage?

looks like you can get a Mallory version right here at marineengine.com for $188
 
Re: Merc 470 Starter Amperage?

My amp test was done on the bench (no load) and got a reading of 75 amps... It just seemed weak in my opinion.

Thanks for the insights and leads... I'm either going to buy new or see if someone locally can rebuild.

Will keep everyone updated.

Thanks,
 
Re: Merc 470 Starter Amperage?

Ayuh,... Electric motors don't take much amperage, til put under Load....
The Free-spinning Test is pretty much irrevelant...

The fact that it don't work, til ya Beat it,...
I'd say you probably need a New 1, or have that 1 Rebuilt...
 
If they sit chief, it don't take long to corrode. I had same problems initially with a 470 starter and was able to carefully take it apart and clean up, and it has worked for the last year without any problems but depends on how long and where the boat has been. (salt?) I would say the brushes and or field is all corroded. Try and break it down, clean it up and see if anything changes. If not the hammer just aint gonna cut it! lol best of luck, Tom
 
bondo said:
Ayuh,... Electric motors don't take much amperage, til put under Load....
The Free-spinning Test is pretty much irrevelant...
Click to expand...
Agree with Bondo......, and agree with Tom (Browning Marine) as well.
(The smacking with a hammer is causing momentary continuity!)
Often a good cleaning of the brushes and commutater will resurrect a starter motor.

armature_commutator.gif


Now, I have a question.
Most all other manufacturers have gone to the HTGR/PMGR starter motors...... (aka mini starters)!
Amp draw on many of these is reduced some from that of their Non-Gear Reduction counter-part.
If one of these is available for the 470, I'd sure recommend this!
I don't recall having seen one yet.

Food for thought!
 
I was thinking the same thing about changing my starter to a gear reduction type. I believe the one I have on my 1988 is a Delco Remy. The guy that does my starter and hydraulic work told me to bring the starter in and he could tell me if I could use a gear reduction type. I was going to wait until this one craps out but maybe it would be a good time to check into what you are saying Ricardo. P.S. Sorry for not responding until now but was out in the snow for the past two days here outside of Philadelphia. Just haven't had the time to post but I am definitely paying attention to what you are saying about amperage draw on the stock starters on the 470s. If everything isn't just right, the starter tends to work fairly hard on cold starts. Takes a bit of torque to fire up the 470s.
talk to you later, Tom
 
Re: Merc 470 Starter Amperage?

With no load it wouldn't pull any current..the acid test is with a load. If it cranks strong on a healthy, properly tuned motor [ignition timing correct] without heating up cables then its OK... if it falls short of that naturally you have a problem. These engines are notorious beasts for hard cranking. It is a large displacement engine for a 4-banger but why should it be tougher than a 6 or a V8? One thing's for sure...they don't start unless they're cranked over fast.
 
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