Incedibly stupid beta 20 wiring question.

[potentillaCO32]

I have an incredibly stupid question.

I am refitting my contessa completely and have got to the engine, which is a beta 20.

I don't want to pull it out at the moment and access to the rear of the alternator and starter motor is impossible without taking the engine out at the moment. So I can't see where all the wires go.
However i have rewired the boat, other than to the engine and the previous owner had just cut all the wires from the engine including the main harness to the control panel. I've reconnected the main harness loom wires to the control panel and also the main 35mm2 cable from the fused engine starter battery switched supply. Also the engine black earth. So all the connections from the control panel to the engine should be good.

There remain two wires coming out of the back of the engine alongside the main harness and with the acess i have can't 100 percent work out whether they come from starter or alternator.

They are thick 2.5mm+ (maybe a bit thicker) wire. One is red the other brown. I assume the red is the main alternator feed and will go the the engine starter battery switched output supply. The other is brown and i am guessing that also goes to +ve engine starter battery switched supply.
Is this right and should i put inline fuse in close to the battery?

Sorry if this is stupid. Ive looked at the beta wiring diagram and couldnt be 100 percent sure especially around the brown wire.

 

[VicS]

There is a brown wire, but it is only 1mm, which is the "excitation" feed from the ignition switch to the alternator. (40 amp alternator only)
Perhaps you are looking at the brown/white wire , which is 2.5mm and is the main positive feed from the engine to the control panel (via the 40 amp fuse)

The 2.5mm red wire is the feed to the glow plugs

I am looking at the wiring diagram on page 74 here https://www.betamarine.nl/downloads/HandBooks/OM-221-20031-HE-REV29-1121.pdf

 

[oilybilge]

Fwiw my beta 20 only has the harness and the big + and - cables

 

[Boater Sam]

If one is the solenoid wire, putting 12v on it will engage the starter. Does that help?
Could you use a mirror or a phone to see?
Alternator will likely have 3 wires, +ve, (possibly thicker than 2.5mm), D+ and W for the tacho.

 

[Tranona]

The only connection to the start battery is the main +ve to the starter motor and -ve to the engine block at a convenient point. No need for a fuse. It is not clear how you have connected the loom to the engine given that all the original wires were cut. Do you have a new loom plugged into the multipin plug of the engine loom?

 

[potentillaCO32]

The only connection to the start battery is the main +ve to the starter motor and -ve to the engine block at a convenient point. No need for a fuse. It is not clear how you have connected the loom to the engine given that all the original wires were cut. Do you have a new loom plugged into the multipin plug of the engine loom?

The loom was cut straight through and i reconnected each wire from the panel to the loom with wago inline connectors.

 

[VicS]

If one is the solenoid wire, putting 12v on it will engage the starter. Does that help?
Could you use a mirror or a phone to see?
Alternator will likely have 3 wires, +ve, (possibly thicker than 2.5mm), D+ and W for the tacho.

It depends on what alternator is fitted.

The manual shows the wiring for 40amp, 75amp, 120amp and 55amp isolated negative alternators

 

[Concerto]

Why have you not spoken to Beta? You will find them very helpful and should be able to answer your query over the phone. I once had a problem with my Beta that I thought needed the starter motor removed. I could not see how to remove one bolt and the chat I spoke to was not sure, so he went on to the factory floor and checked, then called me back with the answer. Their advice will be much better than trying to work out who has given you the correct answer in this thread.

 

[Boater Sam]

It depends on what alternator is fitted.

The manual shows the wiring for 40amp, 75amp, 120amp and 55amp isolated negative alternators

I did say "likely".
I am aware that later alternators differ and he may not have a tacho.

 

[PaulRainbow]

There is a brown wire, but it is only 1mm, which is the "excitation" feed from the ignition switch to the alternator. (40 amp alternator only)
Perhaps you are looking at the brown/white wire , which is 2.5mm and is the main positive feed from the engine to the control panel (via the 40 amp fuse)

The 2.5mm red wire is the feed to the glow plugs

I am looking at the wiring diagram on page 74 here https://www.betamarine.nl/downloads/HandBooks/OM-221-20031-HE-REV29-1121.pdf

I think you're right.

Easy to confirm the red wires purpose, test for continuity between it and one of the glow plugs.

 

[PaulRainbow]

If one is the solenoid wire, putting 12v on it will engage the starter. Does that help?
Could you use a mirror or a phone to see?
Alternator will likely have 3 wires, +ve, (possibly thicker than 2.5mm), D+ and W for the tacho.

Why don't you look at the diagram in post #12 ?

 

[potentillaCO32]

Fwiw my beta 20 only has the harness and the big + and - cables

Unbelievably after much crawling mine is the same.

The brown and red wires go under and behind the engine to a heater that was ripped out.

Sorry everyone but you know the contortion like space on these things