How to wire a 1.5 BMC starter motor to engine on my boat

[Squirrel1956]

Can anyone help me with supplying a simple diagram to help me wire up a starter motor to a BMC 1.5 engine please ?

[Tony Brooks]

 

Here is the correct one, its actually showing the test procedure so ignore all the volt meters.

 

Its a generic diagram but its how I would wire your starter. Plenty more generic wiring diagrams on my website as is the text relating to those voltmeters.

 

It is very likely that other wires are attached to the nut & stud terminal on the starter where the THICK red wire goes, one could well the the thinner red wire that I show running from the master switch to ignition switch.

 

Edited September 24, 2020 by Tony Brooks

[Tony Brooks]

Here is a better one;

 

[Tracy D'arth]

I think that battery connected unfused cables now need to be 50 mm square cross sectional area not 40 mm sq?

[Jen-in-Wellies]

11 minutes ago, Tracy D'arth said:

I think that battery connected unfused cables now need to be 50 mm square cross sectional area not 40 mm sq?

Still 25mm² minimum in the BSS requirements for private boats.

 

[Tracy D'arth]

35 minutes ago, Jen-in-Wellies said:

Still 25mm² minimum in the BSS requirements for private boats.

 

Good, we need all the spare copper for charging cars. Sorry to mislead the OP.

[TNLI]

On 24/09/2020 at 18:24, Tony Brooks said:

Here is a better one;

 

 

 Most starter solenoids draw around 30 amps or more in a few cases. I don't trust simple ignition switches with more than 20A so will be fitting a 12v relay rated at 100A near the starter so I can use the positive battery and earth connections for the motor. 

  If it's less than 20A, please let me know!

[Tony Brooks]

I don't have a starter to measure the resistance of the two solenoid coils but a web source gives about 0.5 ohms for the pull in coil and about 1 amp for the hold in coil. Those seem credible to me. So initially the draw will be 12/0.5 = 24 amps, plus hold in coil 12/1 = 12 amps. So for a few milliseconds until the contacts close about 36 amps but then 12 amps. I would be far more concerned about the glow plug current if it is controlled by the ignition switch because they will draw between abut 24 and 50 amps continuously. If you do use relays or extra solenoid on either circuit do not mount it/hem on the engine because vibrations tend to shorten their life.