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From: rls@ihu1g.UUCP (r.l. schieve)
Newsgroups: net.rec.boat
Subject: Re: Outboard water pressure
Message-ID: <620@ihu1g.UUCP>
Date: Fri, 17-May-85 09:08:28 EDT
Article-I.D.: ihu1g.620
Posted: Fri May 17 09:08:28 1985
Date-Received: Sat, 18-May-85 02:11:22 EDT
References: <53@biomed.UUCP>
Organization: AT&T Bell Laboratories
Lines: 37

> Outboard engines use a rubber impeller as a cooling water pump and from what
> I have been told by several outboard mechanics is that this part will burn
> up and turn into little rubber bands in seconds if the engine is not
> immersed in water while running.  Once this part fails, the engine will
> overheat and (probably several minutes later) set off the high temperature
> "hot" horn (which only the larger engines are equipped with) indicating that
> the pistons have or are about to seize.  You are supposed to keep an eye on
> the little "water indicator" hole that pisses into the water while the
> engine is running assuring you that the rubber impeller is still turning O.K.
>   OMC (Johnson/Evinrude) sells a water pressure gage which mounts on the
> dashboard and comes "with tubing" so I suppose you have to run a hose from
> the engine to the gage.  Still, you have to keep an eye on the gage.
>   I have installed a fluid pressure switch at the engine by cutting the hose
> that runs to the "water indicator" and inserting a tee connector to feed the
> switch.  A pair of wires run up to the dashboard where a piezo buzzer is
> mounted.  The buzzer sounds for a few seconds on start-up until the water
> pressure rises which clicks the switch contacts open.  The power is tapped
> from the "ignition on" + lead so all is quiet when the key is off.  This
> also lets me know when I have left the key on without the engine running.
> Any comments ??????
> Bob Lagasse Biomed Eng. MGH

Sounds like a good idea but you may be a bit paranoid.  I know how
expensive outboards can be but I also know that they are more durable
than most dealers would have you believe.

I do have a question about the water pressure gauge OMC provides.
Is it a go/no go indication or is it calibrated in PSI.  I haven't
had to change the water pump on my 140 hp yet but I have on smaller
OMC engines and what often happens is several of the impeller fins
or blades (whatever they are called) break off.  The pump still
functions but at reduced capacity.  Having seen this happen it seems
wise to periodically replace the impeller but I do admit I had a lot
more confidence tearing into a 20 year old 18 hp than a relatively
new 140 hp with a replacement value somewhere around $6000.

				Rick Schieve