[C320-list] Is the starter motor the culprit?

[ptormey 4square.net]

The gunk in a starter motor is likely the dust from the brushes mixed with some stray oil.  

When we use to rebuild motors (back in my Navy days) the first thing was to wash them out. Common DC motors have brushes made of some carbon mix that conducts the juice onto the rotor through a commutator. The bushes wear down by design; carbon is soft. The brushes also wear down the commutator which is a soft copper series of 'fingers' on the rotor. 

The stray carbon dust actually shorts out the juice that's supposed to get to the rotor AND as the brushes wear down the spring that holds them in place give up some of the pressure making a weaker connection.

The symptom is that the starter turns slower, takes more amps and can usually be temporality boosted with a higher voltage.

Fortunately, stater motors are designed to be rebuild. They clean them up, check for any shorts, undercut the commutator "fingers", replace any bearing as needed and probably replace the solenoid that kicks the starter gear into the flywheel gears.  My guy even painted it Yanmar grey (7 years ago $125 USD) with overnight delivery!



Pat
Pat Tormey
s/v Blues Skies
Newport RI

-----Original Message-----
From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of Bob Hoyt via C320-list
Sent: Monday, March 27, 2023 4:34 PM
To: c320-list at lists.catalina320.com
Cc: Bob Hoyt <rehoyt at gmail.com>
Subject: [C320-list] Is the starter motor the culprit?

In this month's Cruising World there is a story (Renovating Your Starter
Motor) about a starter motor that was requiring more amps to start over time. The owner took it apart and found it was full of "gunk". This could be my problem. I queried the forum about a year ago that a group 27 dedicated starting battery would turn over but not start my Perkins M30 engine. I then tested my existing batteries that consist of two pairs of 6 volt Duracell golf cart batteries in series. Similarly, the house pair and the motor pair will turn over but not start the engine. It takes all four batteries to start the engine. They are new  and read about 12.8  volts.
The voltage at the starter motor is the same as at the battery. After activating the glow plugs and starting the engine the voltage drops to 11.7. The resistance across the starter motor with everything off is 9.92 M which I believe is too high.  All battery terminals and engine ground have been cleaned and look good 1. Is there enough proof to pull the starter out or should I try to connect a separate 12 volt battery to the starter  with battery cables to see if that will start the engine as the first test?
2. How hard is it to pull the starter motor?
3. I cannot find any tech articles about this in the forum archives 4. My situation is complicated by the fact that my boat is at the Navy base in Pensacola and it is very hard to get contractors to make a  service call 4. Also, the sole starter motor repair shop shut its doors this year.

I would appreciate any guidance

Bob Hoyt
"Ikigai"
1994 C-320 Hull #58
Pensacola, FL

-- 

*Robert (Bob) Hoyt MD, FACP, FAMIA, ABPM-CI*

*Associate Clinical Professor, Department of Internal Medicine*

*Virginia Commonwealth University*

*Richmond, VA*


*CAPT (Ret) USN*

InformaticsEducation.org  <http://InformaticsEducation.org>

nocodedatascience.net
rehoyt at gmail.com

Cell: 850-384-5235

QR Code for CV