525 efi issue
 

So here is the story: I have a 2008 formula 353 with twin 525 efi. The one motor stopped running, and wouldn't start up again. My vessel view came up with a code crank/cam sensor. Because it wouldn't fire, I assumed it was the crank sensor. I bought a new crank sensor through gm. It still wouldn't fire. So I moved the crank sensor and cam sensor from the good motor to the bad motor. Fired up and ran at idle for about 5 minutes. I turned it off, celebrated, and started to clean up. Then I tried to start again, wouldn't fire. I took the crank and cam sensor from the bad motor and put it in the good motor, fired right up, multiple times.
Any ideas?
I have heard that those sensors are on a 5 volt reference loop. A friend of mine, with an 8.1 suburban, had a similar problem that was throwing a crank sensor warning, but it turned out to be another sensor on that same 5 volt loop.
HELP!!!! Thanks

On our 525 boat the oil drive / cam sensor was the problem. Sometimes the crank sensor shows up because of a no start or slow start condition. Have you scanned with a Rinda? If you want to stay on top of your 525s get one. It will save you time and money.

What I would like is to get is my hands on a wiring diagram. Yes, the sensors are mercury,

first and foremost you need to post your engine serial numbers.

Early 525 where set up differently than later ones for a jist of info. This all goes by engine serial numbers - year model means nothing for marine engine apps.

Also there is issues with the wiring harness per certain engine serial number segments

OM959462 bad one, OM959462 good one

Haha 2 engines with the same serial number. Oh I do not miss to much.

OM959835 good one. The problem is eating dinner after 13 hr work day and typing.

The saga continues. I put the computer from the good motor on to the bad motor, it fired up and ran. Then after starting 3 more times, it wouldn't start. Put the computer back on the good motor, it worked fine. Checked fuel pressure, ok. Next check firing of plugs .

Well you proved it’s not the computer then. The Rinda will help you narrrow it down. The smart craft doesn’t always point to the exact problem/sensor.

try unpluging the water pressure sensor - did your problem go away ? IF not plug that back in and see if that help but before check out the connection / connector real well. If problem still exists -- NEXT unplug your fuel pressure sensor - did problem go away ? Check connections and connector - plug back in - does problem still exists ?

Yes, that's my next step. After replacing batteries, the motor fired right up. It ran until about 140 degrees, shut off and never started again. I put fuel pressure gauge back on and had 40-45 psi. I think it must be a sensor that is heating up and then it shuts the motor off. It must not cool off for a long time.

I meant "It MUST cool off for a long time".

Any updates here good or bad ?

Still digging. Going to buy Rinda and test sensors. Tried swapping things to no success.

Have you checked for 5V on the sensors?
Check any one of them (water pressure or other) to see if you have a full 5V

Yes, 5 volts.