Re: [OMC-Boats] fuses cont'd

Jeff,

What you are bringing up is a very valid concern. You can get much better answers from several good books and published standards on marine electrical systems. Do you have basic electrical skills/understanding? Do you own decent electrical trouble shooting tools commonly available at your local Radio Shack store? A decent DVM will allow you to measure current flows of any branch circuit device and determine appropriate fuse sizes, right-sized for your specific application.

Generally speaking, you want to the fuse rated about 25% higher than the maximum load to provide the best protection. OMC went from circuit breakers, to no protection, to the "blob" encased fuse (rather like a fusible link) on the main alternator feed and the main tilt motor feed. My original 66 Sportsman had no fuse protection on the alternator, battery, or tilt motor. Go figure?
So you might want to add those if there are un-protected high-current draw circuits in your boat.

I also find the Blue Sea System website a valuable resource. Check it out, lotsa great products and advice at:
http://bluesea.com/

You can also get ideas from my re-wiring project at:
http://hhscott.com/evinrude/images/hp/helm_project_wiring/hp_wire_tn.html

As a result of my helm re-wiring project, I have added several addition fuses: 1) 2nd battery fuse protected, 2) Alternator feed (in updated OMC engine harness), 3) tilt motor feed (in updated OMC engine harness), 4) new Blue Seas Main Helm DC distribution panel (6) fuses), 5) all 10 helm (Blue Seas WeatherPak) control switches all individually fused, 6) 8 electronic CruzPro instrument fuses on small sub dist panels, 7) inline fuses for battery charger, trim tabs, and aux vent fans. When I did this project (over the winter) I rewired the entire helm and I took accurate in-circuit current flow measurements and sized each fuse as small as practically possible, while still providing safe and reliable operation. I think the first summer of operation, I had to replace one fuse from 2 amp to 4 amp, because I didn't allow enough reserve. Not bad when you count up the total number of fuses at something around 30+.

Lee Shuster

-----Original Message-----
From: omc-boats-bounces@... [mailto:omc-boats-bounces@...ultimate.com] On Behalf Of jd
Sent: Thursday, August 06, 2009 9:26 AM
To: Evinrude & Johnson Boats of the 1960's and 70's
Subject: [OMC-Boats] fuses cont'd

a couple more questions.......

- My manual shows many leads coming off the IGN post of my ignition
switch. Plus i've added a couple more. So total is OIL TEMP,
WATER TEMP, BALLAST RESISTOR, CARB WIRE, DEPTH, STEREO, and i think
a couple more i can't remember off the top of my head. Way too many
to try and cram into ring terminals and connect to that little
post. So I ran a 10ga wire to a "satellite" post near by and have
a few things coming off that instead. Any probs with doing that?

- i flipped through a book in a marine store the other day that seemed to emphasize having a fuse on practically everything. They even strongly recommended a fuse (or breaker) on the positive battery lead
between the batt positive post and the starter. Is that needed?
The old 60's manual doesn't show one there. But I want to update
safety wise as much as possible. Is that one overkill? Any
other places where the manual doesn't show a fuse but it might be good to update things and add one?

thanks!
Jeff
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Received on Thursday, 6 August 2009