Starter circuit breaker keeps tripping

[Bluechart]

It could be a weak battery, How old is yours?

[Dave9111]

Remove the starter and take it to an Auto Electric shop.

Tell them you want the starter tested under load.

If its going bad they will tell you.

Get rid of the junk circuit breaker you bought. If you really want to protect your battery and cable, get a fuse designed to do that. It's not going to be cheap, and you likely won't get it off Ebay or Amazon. You will need to size it to the max amp rating of your starter motor. It should be a time delay fuse.
Cheap breakers are not what you need or want. Because you will have a fuse, you will need to carry a spare or have some way to defeat it in case you blow it away from the dock. They won't be for sale at the Auto parts store or local marine store.

[Tmint]

There are two types of breakers, thermal and magnetic trip. A mag trip breaker will trip instantly when the current exceeds the trip point. A thermal trip breaker has a shallower time-current curve and can handle excess current for some period of time depending on the time-current curve--the higher the current, the lower the time to trip. It takes a higher value mag trip breaker to handle the same motor current inrush as a thermal trip breaker. Fuses also can be either fast, or slow blow.



However, that is probably not relevant to your intermittent problem. You may have an intermittent short (also called a flying short), a loose winding that only shorts out when the hot metal of the motor expands, but not when it is cold.



Apologies if I am repeating another answer--I have not read all the comments.

[Uncle Bob]

Originally Posted by Mickeyrouse

Update on tripping circuit breaker.
I am embarrassed to say I was incorrectly interpreting the behavior of the circuit breaker. It is a new (to me) type I have never encountered before, and is apparently designed to be used in switching. It has a button on top and a lever on the side. I’m thinking the button up-lever out means tripped, which is the opposite of what it means. Until I put the ohm meter on it I was thinking wrong. But I replaced it anyway with the Blue Seas 250 amp fuse and fuse block. Engine still didn’t crank.
So my buddy Hank comes down and saves me from myself. We checked for current at each connection point from the battery, starter, keyswitch, starter solenoid, etc. in the process of which- the engine cranked and ran. The tell tale sign was the oil pressure buzzer intermittently going off and on while the key was on. Checked the plugs of the wiring harness to buzzer and instrument-switch panel. Pretty corroded. Installed a new wiring harness a couple weeks ago and apparently the new harness disturbed surface corrosion on the contact pins. The harness plug was intermittently opening the circuit. Cleaned the male pins with sandpaper and the female pins with the Dremel burnishing tool running on slowest speed. Applied dielectric grease to the plugs. Everything starting and running fine now. Incidentally, we put a clamp meter on the cable from the battery to the starter. Starting a cold engine, it drew 162 amps.
Regarding condition of starter motor: It’s brand new this summer, and probably has less than 30 starts on it. Took it to a starter shop. The tech opened it up, says it looks brand new. As well it should. I am good at letting fear of a complicated solution obscure checking for the simplest thing first.
As computer reparmen used to tell me, they would always ask: “ Is it plugged in?”

Thank you for the honest update and resolution, so many never respond with the concluding information.
(But you know you will still get earnest posts from those that cant or wont read past the first couple of posts, offering advice, don't you.)

[Mickeyrouse]

Originally Posted by Bluechart

It could be a weak battery, How old is yours?

About 4 months

[Mickeyrouse]

Originally Posted by David Mathis

Your starter is ready for a rebuild or replacement. Do it now before it fails at a critical time. The tripping breaker is your friend, it's telling you about a problem. Listen to it.

Brand new this summer.

Check my “ final report.”

[Mickeyrouse]

Further update:
Been sailing a lot this past week. I’ve cranked the engine probably 25 times. Not a single hiccup. Starts in what seems like two or three complete rev’s of the engine.