Well, I have had this problem happen to me twice now with my boat. It
is a 1978 Sea Star 165 hp I/O Mercruiser (Chevy Block?). It cranks
real slow but will fire if the battery is charged up. I took it out on
the lake it started up, ran it around a bit, anchored, did a little
fishing, wasn't getting any hits so I decided to move onto a different
spot. It would BARELY crank, no clicking, and actually the battery
would allow me to run the blower and such. So, after that, I had
someone tow me in. I bought a new battery (so now I have two). I took
it out yesterday, same problem, I hooked up the other battery while on
the lake and cranked it up and it started (BARELY). So I drove it to
the launch and shut it down to pull it up on the trailer, before I put
it on the trailer I thought that I would give it another shot. It
BARELY cranked again and wouldn't start. Hmmmm. I have a couple of
thoughts on it, but I don't want to go throwing parts at it when they
are needed. Any help would be appreciated though. I am thinking one
of three options he Starter, Alternator, or Voltage Regulator. I
did however notice that the battery cables were EXTREMELY hot on the
ground side and a little hot on the positive side. But, I did tighten
them up while I was out there so it wasn't a battery cable problem.
There is no corrosion on the cables whatsoever, so that shouldn't be a
problem. The starter is engaging, but this is what is puzzling me.

What are your thoughts?

smooth

Cables only get hot if there's voltage being dropped across them, or across
the connection. Connections need to be bright shiny metal before they're
bolted up and then they need to be so mechanically secure that the
connection is "gas tight;" i.e. there's no possibility of air getting in to
cause oxidation, even after it's been shaken around a lot. I use a wire
brush in a Dremel tool to "polish" the connecting points (other than the
battery posts). For the posts, there are special wire brushes.

Besides the connections you unbolt, there's also a connection, soldered or
crimped, inside the cable between the conductor and the end fittings.

It's also possible that enough strands have broken that you have too small a
conductor.

You can find the voltage drop with a meter while someone else hits the
starter switch. Note that an ohm meter is not much use in finding the
problem. 0.01 ohm will typically drop a volt during starting and generate
100 watts of heat.

On a twelve volt system, I'd look for at least 8 volts at the starter while
cranking. Make sure the whole circuit, from negative battery post, thru
ground straps, cables and the engine block is a good low impedance circuit.

Roger

http://home.insightbb.com/~derbyrm

"smoothz1977" wrote in message
oups.com...
Well, I have had this problem happen to me twice now with my boat. It
is a 1978 Sea Star 165 hp I/O Mercruiser (Chevy Block?). It cranks
real slow but will fire if the battery is charged up. I took it out on
the lake it started up, ran it around a bit, anchored, did a little
fishing, wasn't getting any hits so I decided to move onto a different
spot. It would BARELY crank, no clicking, and actually the battery
would allow me to run the blower and such. So, after that, I had
someone tow me in. I bought a new battery (so now I have two). I took
it out yesterday, same problem, I hooked up the other battery while on
the lake and cranked it up and it started (BARELY). So I drove it to
the launch and shut it down to pull it up on the trailer, before I put
it on the trailer I thought that I would give it another shot. It
BARELY cranked again and wouldn't start. Hmmmm. I have a couple of
thoughts on it, but I don't want to go throwing parts at it when they
are needed. Any help would be appreciated though. I am thinking one
of three options he Starter, Alternator, or Voltage Regulator. I
did however notice that the battery cables were EXTREMELY hot on the
ground side and a little hot on the positive side. But, I did tighten
them up while I was out there so it wasn't a battery cable problem.
There is no corrosion on the cables whatsoever, so that shouldn't be a
problem. The starter is engaging, but this is what is puzzling me.

What are your thoughts?

smooth

Okay, understandable, however, do you think that the starter is pulling
too much of a load causing the heat?

A starter is a series wound DC motor. It will pull several hundred amperes
if locked (& very little current while spinning free). That's why one has
heavy cables and relays (solenoids).

It's possible that you have a shorted turn, but you mentioned a hot cable,
and that fix is cheap and easy. Only if the cables are very good would I
pull the starter and take it to an automotive electric shop to be put on a
growler. (If you do, then while it's out, get new brushes and bushings.)
(It's almost never the starter.)

Measure the voltage drops. I'll bet your starter has five volts or less
across it while trying to crank.

Roger

http://home.insightbb.com/~derbyrm

"smoothz1977" wrote in message
oups.com...
Okay, understandable, however, do you think that the starter is pulling
too much of a load causing the heat?