crusader twin 305s

i am having what seems to be eletrical problems i cant start engines 1 by 1 have to start them at the same time i have two iginition switches but with the motors running if i turn one key off both motors shut off any ideas where to start...........thanks brian

Yes, I would say that you have an electrical problem!


Both engines should be separated by the engine harness/hull harness/helm locations. Meaning that the Port engine battery bank should power the Port helm instruments, and the Stbd engine battery bank should power the Stbd helm.
On many boats up to 30 feet or so, the Stbd engine harness/hull harness will include your HLBB (house load battery bank) of which powers the main cabin needs, Nav Gear, etc. when selected.
Even when sharing a Port side cranking bank, the harnesses should still separate these engines, instruments, key switches, etc.

Some owners/mechanics will disconnect batteries for the winter. When these are reconnected upon re-commissioning, often a Negative cable is forgotten.
If nothing else has been changed, you may want to begin by tracing all of your cables down.
Make sure that each battery bank makes it's own independant "system negative common" connection to each engine.
IOW, Do NOT share Negative connections between battery banks. We want redundancy here!

By chance do you have an OEM wiring schematic.... and if so, has any of this been changed from OEM?
Can you post photos of it?

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honestly this is my first inboard boat so i have no clue where to start with this what is OEM? and yes i can get some pics

i will say this is an old still points system i have dual battery with dual switch but all wires go to one battery the one battery only has one hot wire and one ground wire

OEM = Original Equipment Manufacturer.

OK... with twins we typically have two MBSS's (main battery selector switch).... one for each engine's battery bank.
This gives the oportunity for each engine to have a dedicated cranking battery..... (or battery bank)!
In many cases, the Stbd engine will have two battery banks. One will be a cranking battery, the other bank will be a much larger bank of Deep Cycle batteries.
The MBSS let's us select which bank we want to be using for the usage.

From what you're saying, you have one battery bank ONLY for both engines????
Not Good! NO redundancy and/or NO "reserve" battery!

If this is any size cruiser type boat, you'll certainly want to change this arrangement, IMO.

Yes.... pictures would be great!

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what do want pics of? ill get them for you