Re: [OMC-Boats] overheating

Jeff,

I wonder if the "instrumentation issue" or electrical wiring / grounding
"mystery" is as simple as realizing that you have a temperature sender
incompatibility? I trust you (or your mechanic) do realize the original
OMC boats all used a simple "idiot" light (at least from the factory)?
The original temp sensor for the light is a simple "switch" that allows
the "HOT" light to come on at a pre-determined temp. A "temp" gauge
sensor on the other hand changes resistance, typically the Teleflex or
Stewart Warner type temp sensors are commonly found on American boats.

Anyways, thanks for the update and keep after it, you'll get there! Tell
your mechanic Buicks aren't really much different from Chevies....

Lee

-----Original Message-----
From: omc-boats-bounces@...
[mailto:omc-boats-bounces@...] On Behalf Of JEFF DOOD
Sent: Friday, August 15, 2008 12:13 AM
To: Evinrude & Johnson Boats of the 1960's and 70's
Subject: Re: [OMC-Boats] overheating

On Aug 14, 2008, at 2:00 PM, Lee Shuster wrote:

> Sorry, for not following this saga more closely, but is in the same
> boat that had the confusion over (even/odd-fire) distributors? How did

> that get resolved?

same boat. finally got the original distributer on there after lots
of trial and error. that helped but didn't completely resolve.
ended up being a carb thing that was causing the mid throttle
backfiring (not sure why). then after backfiring went away, lasted
for a few minutes, then engine developed internal noises - like
"rebuild" type noises. that's the way my luck seems to work. so
fortunately had a spare engine. swapped, a bit more carb stuff, and
viola - no more backfiring or engine noise. actually had it in the
water at full throttle for a total of about 5 minutes since then.
Now is this overheating issue. Well, apparantly not actual
overheating - just the appearance of overheating.
>
>
> Not that it should really matter, But what's the source of this
> current Buick V6? 231 (odd or even fire?) or 225 (odd fore)? As
> someone else pointed out, something as simple as the wrong manifold
> gaskets can lead to problems.

buick odd fire (as best as i can tell). it came from another boat -
bought used from a guy last summer.
>
>
> Again, I go back to someone else's suggestion: Get a decent
> (hopefully)
> color flow diagram of the entire cooling system. Then start breaking
> the system down into it's individual parts. The original OMC manuals
> as well as the third-party SELOC & Clymer's are must have for you and
> your mechanic. A good understanding of the "theory of OMC cooling" is
> essential and can hopefully reduce the "chasing one's tale" approach
> to troubleshooting. This is part of what I meant in an earlier post
> about checking something as simple as the proper connections for the
> four hose mounting locations for each cylinder bank's
> manifold-to-thermostat hose routing. Direction of flow matters, kinda
> like + or - in electricity.
> Also what spec T-Stat are you running? Remember this is another area
> cars and boats differ. OMC spec'd at 140 def F 'stat. Cars are
> typically higher.
>
> What is meant by " So he checked for blockage etc - one part of one
> manifold was running
> very hot, while the others were fine. swapped out that manifold.
> Now engine is running at normal temps (albeit, on the hose),......
>
> Not sure if this mean manifold is fine to the touch? Or what method or

> metric if instruments are suspect? How about some actual data points,
> in degrees F?

he's checking everything with some sort of super duper scope which reads
the temp in F. and i guess he can check specific parts of the engine
with it, hence being able to pin point that 1/2 one manifold was
overheating.
>
>
> I understand what you are saying about gauges/instrument sensors, but
> remember that is only one point of reference.
> You or your mechanic should be checking flow rates @... various points in

> the entire cooling system. Has anyone pulled the ends off the
> manifolds and checked for any restrictions or blockages? Swapping
> parts, especially used ones, when they are KNOWN to be good could lead

> one to draw the wrong or inconclusive results.
>
> Don't get too frustrated, sounds like you are making progress. Still
> some quality boating time this year yet to go.

thanks - yeah, it seems to be narrowing down. talked to him several
times throughout today. at end of the day, it appeared to be down
to just a wiring issue somehow. (again, just on the hose). The
temp of engine is now uniform and normal after swapping out
manifold. Rigging up a gauge straight off battery is confirming
that. his scope is confirming that. But when it's connected into
the dash stuff the needle moves right over to 240. Even without the
engine running. Definitely some elec wierdness, however not as
simple as you might expect. There's two guys on it, and neither can
trace down why it's doing that. different gauges are doing the same
thing, so not a gauge problem. He's already considered grounding
issues and that wasn't it. 3 different sending units show same
thing. So he's stuck. Will call him tomorrow morn. I am
actually feeling pretty good about things right now though. A simple
wiring thing at this point. However, I can't water test without a
perfectly functioning gauge. So although it seems minor, until it's
resolved i am still stuck out of water. But atleast it's not
overheating - atleast on the hose. The one big thing i have
learned through all this so far is that testing on the hose is pretty
worthless. Testing in the water is really essential. I've also
learned that my mechanic is swearing to never work on another buick
engine again.

wish i had the time to learn to do most of this myself. i am hating
having to rely on a mechanic who hates my engine! But i understand his
frustration. There have been a lot of weird issues with this whole
thing.

jeff

>
>
> Lee
>
> -----Original Message-----
> From: omc-boats-bounces@...
> [mailto:omc-boats-bounces@...] On Behalf Of JEFF DOOD
> Sent: Thursday, August 14, 2008 1:39 PM
> To: Evinrude & Johnson Boats of the 1960's and 70's
> Subject: Re: [OMC-Boats] overheating
>
> well.......frustratingly close to getting the problem solved. but
> still not there. it's very weird. here's whats going on - my
> mechanic has had it for a couple days. it was overheating on the
> hose for him also (good thing, so not just happening underway). So
> he checked for blockage etc - one part of one manifold was running
> very hot, while the others were fine. swapped out that manifold.
> Now engine is running at normal temps (albeit, on the hose), but
> every gauge he hooks up to it says it's overheating. He swapped out
> all the sending units to different ones from another engine (not new,
> but different). Still, even trying different gauges, it says it's
> overheating. He is confirming the actual engine temps with a special
> heat sensor thing he uses - same as fire dept eqpt, say he trusts it
> more than any gauge. Could be the engine IS actually overheating and
> his eqpt is bad - but i don't think so - it sounds legit. maybe
> other mechanics use this too when they can't trust any gauge.
> nonetheless, assuming that's not the prob - then it would seem like
> the sending units. but again, he swapped those out too.
> possibility of 2-3 bad sending units in a row, but that seems like a
> stretch. any idea?
>
> if it were a crack, or blockage, or bad thermostat, or hoses, etc -
> the engine would be running hot - which it supposedly isn't. yet
> trying different gauges and sending units didn't make any
> difference. Any other parts of the chain we're forgetting about
> here?
>
> the weekend is coming and i'm so close to having this thing usable
> again its driving me nuts!!!
>
> jeff
>
>
>
>
> On Aug 11, 2008, at 11:57 AM, Ethan Brodsky wrote:
>
>> On Mon, 11 Aug 2008, JEFF DOOD wrote:
>>> i am getting very close to being able to use my boat finally, won't

>>> go into all the recent past history but it's been a journey. long
>>> story short, i have a different engine in it now. another buick
>>> v-6. runs, starts, sounds good, doesn't backfire and lose all
>>> power
>>> at mid throttle, etc. only one problem. when on the hose, it's
>>> operating at normal temps. when under load, the temp gauge is
>>> just
>>> races right up to the overheat range. thought i might be the
>>> gauge,
>>> no such luck. on 2nd test, same thing. idling at dock it temp
>>> gauge barely moves. but after about 10 seconds at full throttle it
>>> starts moving up and within about 30 it's almost pegged. putting
>>> on
>>> a new sending unit next, seeing if that does anything. if it's
>>> got
>>> blockage somewhere, then wouldn't it heat up while on the hose at
>>> the mechanic's shop also? it's getting water through there.
>>> pretty
>>> sure mechanic replaced impeller at last go around. and there
>>> doesn't seem to be any obvious leaks or cracks anywhere in the
>>> manifolds. any ideas?
>>
>> My first thought would be to check the thermostat? Is it working.
>> Is it
>> the right one? Engines in cars usually ship with thermostats that
>> open around 180-200F, while marine engines are usually supposed to
>> run
>
>> around 140-180F. If you've got an automotive thermostat in there,
>> the
>
>> gauge will show it as overheating all the time, and it'll be running
>> a
>
>> lot hotter than it should. If it's sticking shut, that would also
>> cause overheating.
>>
>> If that's not it, I'd ensure that all the cooling passages are open
>> by
>
>> testing them one at a time. Look at a drawing of the coolant
>> ciculation patterns (in the service manual) and hook up a garden hose

>> (engine
>> off) to
>> each of the inlets and make water comes out the corresponding outlet.
>> Check both passages in each exhaust header and the engine block
>> passages.
>> Also try opening the two drain cocks on each side of the engine and
>> see if you have water pouring out.
>>
>> Ethan
>>
>> --
>> Ethan Brodsky
>> _______________________________________________
>> OMC-Boats mailing list
>> OMC-Boats@...
>> http://lists.ultimate.com/mailman/listinfo/omc-boats
>
> _______________________________________________
> OMC-Boats mailing list
> OMC-Boats@...
> http://lists.ultimate.com/mailman/listinfo/omc-boats
> _______________________________________________
> OMC-Boats mailing list
> OMC-Boats@...
> http://lists.ultimate.com/mailman/listinfo/omc-boats

_______________________________________________
OMC-Boats mailing list
OMC-Boats@...
http://lists.ultimate.com/mailman/listinfo/omc-boats
Received on Friday, 15 August 2008