Boat Electrics Help!

[b j p]

Hey guys,

I have a 469 Seahorse with a 50hp Tohatsu Tiller. I've just put a new battery in the boat after the old one carked it. Sometime between removing old battery and installing new one I have developed a problem. The problem is that the electric start, RPM, fuel guage now does not work. The electric tilt/trim, sounder, gps, VHF, lights etc work fine. Seems a little strange that the tilt/trim would work but the electric start wouldn't. Anyone got any suggestions on where I should start looking for the problem?

[Micadogs]

Hi BJP, I would start the investigations with a fuse in the motor. I had a similar issue with my merc 4 stroke. Was fitting a trim guage and blew the fuse. It stopped the motor turning over, but in this case the trim also. Maybe the Tohatsu is set up differently and has a different fuse for starter and trim.

A slight bit of corrosion on a fuse can change it from say a 20AMP to a 2 AMP and current draw will blow the fuse.

Hope that helps? Regards Adam

[b j p]

Thanks Adam. I will check it out after work today. I'm wondering if a fuse on the motor would affect the fuel and RPM gauges also?

[oldboot]

It all depeneds on where the power is sourced from.

Realy worth getting a manual for your motor so you have some wiring diagrames.

quite often there are two sources of supply in your dash, the supply from the motor via the controll loom and the supply from the battery for your accessories.

My trim & tilt supply comes thru the controll loom.....yours may not....or there may be two sources of supply in the controll looms

Is your tilt n trim on the tiller or on the dash.

cheers

[Micadogs]

Hi BJP, when my fuse blew it affected the trim and tilt, the guages and the starter motor. The fuse that I replaced was under the cowling of the engine. As oldboot suggested, grab your manual and look for the starter motor fuse and check that one.

Regards Adam

[b j p]

Tilt/Trim is on the outboard body just behind the tiller (and remotely connected under the gunnel so I don't have to be a gymnast to use it while under throttle. It would be highly coincidental it didn't have something to do with changing the battery (ie. fuse blown etc). It would seem it could still be an "in-motor" fuse.

Appreciate your help gents. Anyone got a good excuse to get me out of work so I can go home and try it now :P

[Willdoe]

Isn't something silly as one of the cables not put on the battery terminals is it? Been there, done that myself.
Willdoe

[testlab]

This is general advice in nature but sounds like there are probably two fuses and two power feed circuits.

One circuit goes to the ignition switch via the loom, so when this switch is on the gauges and starter solenoid can get power. Call this the engine circuit.

The other circuit goes to tilt/trim and accessories. If I am guessing right the tilt/trim will work without the ignition on - so you can tilt the engine when it is not running.

Is there only one battery (+) cable or two? If definitely only one then the circuits probably split near the starter solenoid. If you're handy with a multimeter or test light it should be pretty quick to find.

By the way, was there even a remote possibility of a reverse polarity event? The accesories (sounder, radio, etc) are usually reverse polarity protected and the lights and trim won't really care. But the charging rectifier and regulator, ECU, etc won't like this at all* and they will be connected to the battery via the 'engine' circuit and its fuse. Hence, dead engine circuit but a live accessory circuit.

A wiring diagram and manual goes a long way, as others have already said.

*PS: the sounder/radio will usually each have an internal blocking diode in series with the supply but the engine circuit and its associated charging and ECU may be protected by a crowbar diode - which intentionally causes the fuse to blow by shunting the reversed polarity. On older engines the unregulated rectifier would also act as a shunt but a lot of those didn't have fuses in series and the rectifier and/or stator coils burnt out. Adding a fuse in series with the rectifier output was a cheap way of preventing the rectifier being destroyed.

# edited to fix a few mixed up words... comes from posting after midnight.