Re: [OMC-Boats] overheating - the saga continues

From: Mike Rewegan <mikerewegan@...>
Date: Tue, 26 Aug 2008 12:29:07 -0400 (EDT)

Have you pumped grease in the swivel bearing? Dry swivel area can sometimes allow exh gases to displace water flow from impeller

JEFF DOOD <jdood@...> wrote: still trying to pin this down. still feels very close, but not
enough to take her for a weekend spin. last week mechanic found a
ton of buildup in one of the manifolds. cleaned it out. engine
holds at 170degrees in gear on hose. took to river to test at
dock. at idle it held pretty steady at about 180degrees for a long
time. then when put in forward, in about 2-3 minutes it's right
up to 210degrees. not good - still overheating. so here's
whats been checked so far:

- both manifolds clean now
- sending unit good
- multiple gauges tested, gauge appears good
- both gauge AND heat sensing scope indicate same temp
- water pump/impeller checked today - good
- no kinks in lines

so at this point he is stumped. and i'm limited. so what he is
suggesting now is to replace all the hosing (temporarily) with clear
hosing to see what things look like when the engine is running and
water is flowing. he has done this before i guess. says water
should be solidly filling hoses normally. but if there's air bubbles
flowing by it will indicate something or other. sound right?

anything else in the chain that can be checked?

and of course, everything seems fine when tested on the hose, but then
when in the water under resistance the story changes. the hose is

it's been interesting nonetheless. i am still amazed that the intake
for the water is just this little 1/2" x 2" screen opening. Yet
there's supposedly enough water taken in through that to fill 4-5
5/8" hoses. then exit out at the end through 2 big 2" hoses. How
does all that water get in there through such a little intake?

i have family in town this upcoming weekend and i really want this
thing on the water. i am planning on spending most of my week in his
shop. grrrr.


On Aug 17, 2008, at 4:12 AM, Lee Shuster wrote:

> I ditched the light(s) and re-wired for a "Stewart-Warner-Teleflex"
> type temp sender. Did same for Oil Pressure sender. If there is room
> I've seen some people fit a TEE and run two senders off the same
> orfice.
> Lee
> ________________________________
> From: omc-boats-bounces@... on behalf of JEFF DOOD
> Sent: Sat 8/16/2008 11:51 PM
> To: Evinrude & Johnson Boats of the 1960's and 70's
> Subject: Re: [OMC-Boats] overheating
> hmmmmm = that's an interesting tidbit. i will pass it along to the
> mechanic. i think he is probably already aware of not just hooking
> up a temp gauge to the light wires. but worth mentioning. and
> something else worth noting here - this latest engine has 3
> senders. one for the oil, one for the idiot light, and one for the
> temp gauge. don't know why, because the other engine i only had
> 2. maybe someone tapped a hole for one somewhere along the line?
> to hook up a gauge? i've seen all 3 on this engine. the 2 for
> temp are on slightly different places on the top of the engine.
> i'm sure he knows and/or has thought about the senders being
> different. but then maybe the light sender got into the gauge
> sender's spot somehow.
> how is everyone else hooking up their temp gauges? are they just
> omitting the idiot light and running straight to a gauge? or do
> other people have 2 temp senders on their engines?
> On Aug 15, 2008, at 6:19 PM, Don Mandelas wrote:
>> As I read this Saga it reminds me of the time when I changed the
>> water temperature warning light to a temperature gauge.
>> When I first installed the guage I wasn't exactly sure how to do it.
>> So, On my first attempt I replaced the sending unit inside the
>> thermostate housing for one that works with my tempeature guage, and
>> then, I just installed the guage in place of the light (using the
>> original two boat wires.). Silly me.
>> When I turn the key to the on position the temperature guage pegged
>> on the high side.
>> Then after reading the instructions that came with the temperature
>> gauge I realised I needed to install a third wire to the gauge.
>> After I added the third wire my guage worked fine.
>> I'm sure this isn't whats causing you overheating problem, but
>> thought I would pass it along in case anyone attempts to do the same
>> thing.
>> Don.
>>> Date: Fri, 15 Aug 2008 09:28:28 -0600
>>> From: lee.k.shuster@...
>>> To: omc-boats@...
>>> Subject: 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
>>>> 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
>>>>> _______________________________________________
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Received on Tuesday, 26 August 2008

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