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`72 Evinrude V4 Problem
Hi I know you guys like to argue a lot about politics, but perhaps you
could take a moment to help me out with my problem, and here it is:I have a 1972 Evinrude 85HP V4 Outboard that has been running fine
until it overheated (didn't seize) when the water pump disintegrated.
After the WP came apart, pieces of it messed up the thermostat (or
whatever it is OMC calls it) so I fixed that and the cooling system
works. I took the boat out for a test run and it starts good, idles
good but when you give it full throttle, it seems like the ignition is
severely missing -but only under load- because as soon as the boat gets
on plane, it seems to run fine. It's like spark is jumping to ground
(somewhere other than it should) on one or two cylinders when under
load. I inspected the Spark plug wires and the coil wire and I don't see
anything obviously wrong. I ordered some new wire and new plugs (old
plugs look OK, perhaps a touch blacker than they ought to be, like it's
running a touch rich) I looked into the spark plug holes and pistons
look good and compression is pretty even on all four cyl. I haven't put
in the new wires (waiting for them to arrive UPS) or plugs but I
wondered if anyone else has seen this behavior before. Thanks JM
Chehalis, WA |
Chehalis
Apr 27
2006
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| I rechecked the compression with the engine warmed up and its even on
all cylinders: 125lbs. That's good news. Before I tested it cold and I
had this nagging thought that maybe it needed to be warmed up first to
get an accurate reading. After changing the wires and plugs, it starts easier and seems to run a
little better but I won't know until I get it out into the water where
I can put it under load. I am wondering if maybe I accidentally put too
much oil in the mix... after pulling the new plugs out (after running
it) they seemed a little oily.... might that make it run terrible? JM |
Chehalis
Apr 29
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| What was the tip off that the engine was overheating?
It sounds like you know what you're doing and have thought about several
possible causes. I agree with you that it may be time for at least a new
set of plugs. You may have gotten it hot enough to deposit a little bit of
metal in the plugs that allow them to "pre-ignite" under load. Also, with
the high temp, you may have broken some of the deposits off the cyl head
that must be there after years of running. A good coating of deposits may
not cause a problem but with high temp, you may have cracked deposits with
glowing edges. In short, if the plugs and wires don't do it, I'd be ready
to pull the heads "Chehalis Jeff" <jeffreylmiller@gmail.com> wrote in message |
LD
Apr 28
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| The tip-off was a LOUD buzzer going off in the control unit. Then I
smelled something when I stopped (old oil burning off the power head)
when I took off the outboard cover, I could tell it was hot. I let it
sit for a while and cool off (buzzer stopped buzzing), and then idled
back in (about 1/4 mi.) to the marina. Good thing it was a pretty cold
day. Immediately I assumed it was the water pump. I didn't hear any
predetonation - it was like someone was killing two of the spark plugs
- on and off - until the boat got on plane (took a bit) and then it ran
ok (not great, but acceptable.) I just replaced the spark plug wires and spark plugs, but it's getting
dark and I am getting tired so I'll let you all know tomorrow if the
problem was solved. JM |
Chehalis
Apr 28
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| Looks like you are not getting alot of responses. I really can't help but
it is interesting to read in that I have a 72ish Johnson 4cyl 85hp but it
runs fine. If it were me I'd start calling up places that repair these old
motors and see what they think. Sounds scary though - like at some point it
might be better to get a new engine for your nice boat. good luck - "Chehalis Jeff" <jeffreylmiller@gmail.com> wrote in message |
Johnny88
Apr 27
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| If compression is good, my guess is that the engine is fine. Might want to
try out the new plugs before making any decisions. If that doesn't help,
your problem may be unrelated to the overheating. Which would put you back
to coil, wires, condensor & points, and carburetor. Good luck.
surfnturf |
surfnturf
Apr 28
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| Thanks guys... First, the motor has actually run pretty well and has been very
reliable right up until it overheated. Second I cannot afford to just
buy a new motor or I already would have; but I really kind of enjoy
working on these old eggbeaters. From what I have been told the points
are really rarely ever bad since they act as a low voltage switch
(pre-coil.) I can't imagine the points going bad all of a sudden
either. Now the coil and amplifier are a different matter, both of
which are currently suspect. I also considered a blown head gasket, but
I don't see evidence of it. -Jeff |
Chehalis
Apr 27
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| Check the water jacket gaskets. They could be leaking.
"Chehalis Jeff" <jeffreylmiller@gmail.com> wrote in message |
FREDO
Apr 28
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| I don't think the engine itself is hurt from overheating, or you'd have
more and different problems than you describe. I've got a 74 135hp, if
the wires and plugs don't fix it, look at the coils. Also, I've found
mine to be rather finicky, so perhaps just a good tune up by someone
that knows these oldies but goodies, and does it right, has a tank to
do a link and sync, etc. |
basskisser
Apr 28
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| HI JM As others have said a good tune can't hurt, new plugs, check leads etc.
Sorry to be the odd one again but feeling here is you might have a head
gasket/joint leak so once water really gets flowing it kills a cyl or
cyls from firing. Below is a paste of a very old prior post which should help you tune it
if you want without spending. K |
K.
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| But he said all cylinder compression values were very close. If they
aren't leaking down, then how is that water getting in? |
basskisser
Apr 28
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| This is something that I have and are still considering as a possible
problem. I called a local OMC repair shop and that's what they
suggested - that when the engine gets warm enough and with enough
"suction" on the down stroke it could draw in just enough water (from a
'partially blown head gasket') to affect how it runs under load but not
enough to effect it otherwise. It's a possibility, however I would
think that there should be a way to tell if that's happening without
removing the head(s) and replacing the head gaskets. On the other hand,
that's not really a big, expensive or difficult job so maybe it's
worthwhile doing as a precaution. JM |
Chehalis
Apr 28
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