Re: [OMC-Boats] fuses cont'd

From: jd <jdood@...>
Date: Thu, 6 Aug 2009 22:02:03 -0700

On Aug 6, 2009, at 2:48 PM, Lee Shuster wrote:

> 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.

yeah, i've wired a bunch of stuff with mostly success - no expert, but
i have a pretty good conceptual understanding of it all. My eyes
gloss over when it comes to multi-meters though. I love my trusty
light tester. doesn't have a million setting to choose from.

> 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?

One thing in this sentence is exactly what i was hoping to learn.
That OMC didn't fuse anything for a period of time. My manual isn't
quite for my year, but it has been pretty close to what i have (had)
in the wiring diagram. Almost dead on. Except for a couple glaring
differences. It shows a 60 amp fuse on the alternator lead. A 100
amp fuse near the solenoids for the tilt. And a 30 amp fuse between
the ignition and the main panel. I had nothing on the alternator.
Put an inline 60 amp fuse on today. Had nothing for the panel.
Installed a 30 amp along with my new fuse panel.

The one remaining mystery to solve is the tilt. Maybe mine has the
infamous blob in there somewhere, but i can't really find it. Until
you said just now that some years had nothing, I wasn't too worried
thinking maybe I just can't see it. But now maybe I am one of the
years with nothing. So I'd like to install a 100amp fuse as the
manual shows, but I shopped around today and there aren't a lot of
choice in 100 amp fuses. About only one style that goes up to 100.
And whatever it mounts in surely needs to be screwed to something
solid - not much for that in the engine compartment. Regardless,
100amp seems like a lot. So I am leaning towards putting in the
biggest blade type fuse i can find (i think maybe 40?) in with the
other stuff in the main fuse panel. Wouldn't be near the solenoids
as show in manual, and wouldn't be 100 amps, but perhaps better than
nothing. So it would end up between the ignition and the switch.

> 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:
> You can also get ideas from my re-wiring project at:
> 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+.

Sounds good. I will check it out. Unforturnately I am at the tail
end of two weeks of re-wiring. Hard to go back in at this point, but
I actually think, except the tilt, I've got everything fused that
needs to be (or can be). Only stuff not fused are the gauges - but
only one thing is digital (the depth) and it's fused. Unless I'm
confused, the speedo, tach, fuel, temp, etc aren't really drawing
power and therefore don't need to be fused?

> Lee Shuster
> -----Original Message-----
> From: omc-boats-bounces@... [mailto:omc-boats-bounces@...
> ] 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,
> 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 Friday, 7 August 2009

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