Re: [omc-boats] BAD NEWS

I check compression on all 6 cylinders 3 times each. I found that I have
one bad cylinder that is squirting water out of it when I crank it over and
the compression is low. First test was 100 then 90, then 70. :( The other
cylinders were 125, 125, 130, 130, 145 average. Oh! The oil looks like a
light colored brown mud.

Should I change head gasket and possibly the head or just swap motors with
that 231 that come out of a 83,84 Buick Regal?

I'm still shooting for spring!
Ryan
----- Original Message -----
From: "Ethan Brodsky" <brodskye@...>
To: <omc-boats@...>
Sent: Saturday, December 10, 2005 12:08 AM
Subject: Re: [omc-boats] new member

> On Fri, 9 Dec 2005, Ryan wrote:
>> Ok..I got a compression gage. The guy who loaned it to me said I should
>> check not only the compression but also the tolerance between
>> cylinders??? I assume that means make sure one cylinder isn't way more
>> or less the than others. Any idea what the tolerance is + or - ? Is
>> this necessary?
>
> I recently picked up the factory service manual for the 1970 155 HP OMC
> V-6. It specifies the following procedure for compression testing:
>
> (a) Remove all spark plugs
> (b) Put throttle and choke in wide open position
> (c) Remove wire from coil to distributor cap and ground securely to engine
> (d) Attach remote starter switch to starter assist solenoid
> (e) Insert compression gauge in spark plug port. Crank engine through
> at least 4 compression strokes to obtain the highest possible reading.
> (f) Check compression of each chlinder. Repeat a second time and record
> the highest reading for each cylinder
> (g) The recorded compression pressures are to be considered normal if the
> lowest cylinder pressure reading is more than 75% of the highest
> (h) Example: 129,135,140,121,120,100 - 75% of 140 is 105. Thus, cylinder
> 6
> is less than 75% of number 3. This condition, accompanied by low speed
> missing, indicates an improperly seated valve or worn or broken piston
> ring.
> (i) If one or more cylinders reads low, inject about a tablespoon of
> engine
> oil on top of the piston in low reading cylinder through the spark plug
> port. Repeat compression check on these cylinders
> (1) If compression improves considerably, rings are worn
> (2) If compression does not improve, valves are sticking or seating
> poorly
> (3) If two adjacent cylinders indicate low compression and injecting
> oil does not increase compression, the cause may be a head gasket
> leak between the two cylinders. Engine coolant and/or oil in
> cylinders could result from this defect.
>
> Also, for Mark (the guy with the boat that won't go), the shift coil
> resistance should be between 4.5 and 6.5 ohms, not the 2.xx ohms I
> quoted earlier. The current draw is specified as 2.2 +- 0.2 A.
>
> Ethan
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Received on Saturday, 10 December 2005