Frank Taylor, Jr. wrote:
I'm almost afraid to ask this question for fear of what answers I might get
but here goes:

My boat has a Volvo Penta 5.7 GS engine (carbureted) with 240 hours on it.
It is very well taken care of. Today as I cranked it up, I let go of the
key before the engine caught on and from the sound of things, I knew what
had happened. The engine actually kicked backwards one stroke and sucked up
some water.

I figured, "no problem, this has happened before and I can handle this." I
took out all of the plugs and cranked the engine to let the water blow out
of the cylinders, dried the plugs and put them back in and proceeded to
start the engine.

The engine started but there was a pretty loud knocking sound. I shut it
down to check my plug connections and to check to make sure I had not mixed
up and plugged the wires back in the wrong order and everything was okay. I
started it once again and still had that darned noise.

Any ideas?

I'm really nervous about this one.

Frank



Possibly damaged something but it might also just be the valve lifters
not pumping up.

You say you "dried" the plugs what? there was water all through it??
not likely but? The leads are correct?? you say you checked but ....?

Check the oil, is the level right?? not down? or worse up?? If it's up
the water may have been in the engine before you tried to start it &
some has seeped down into the sump, is the oil milky in any way if so
then it has water in it & you'll need to change it & the filter before
you try again. Once you're sure it has clean oil at the right level;

Start it but don't rev it up, if you have an oil pressure gauge/light
after a short time make sure the oil pressure is up , if not turn it
off. The water contaminated oil might have blocked the pickup if it's
been sitting a while, or the milky oil gets thick almost like cream.
Regardless don't persevere if there's no oil pressure because whatever
the trouble it'll only get worse very quickly.

Assuming it has oil pressure & is running as smoothly as a cold carbed
engine does, then give it a little while to see if it is the valve
lifters (they too don't like ANY water in the oil & get stuck taking a
while to come good but with clean oil they will:-))

If after a couple of minutes the knocking is still there, then try to
determine what it is;

(i) Stuck lifters; can cause lots of noise up at the tappets, but it's a
slower rate than you expect (1/2 engine speed) also the noise is at the
top of the engine. Get say 4 ft of garden hose & put one end to your ear
then hold the other end around the engine (be careful, belts & things
are moving), you'll very quickly be able to pinpoint exactly where the
noise is originating. If it is at the very top of the motor & probably
spread over several cyls on both sides, then good news it probably is
just stuck lifters from having some water in the oil. With clean oil &
filter a little heat & they'll probably come right on their own. You
could even risk increasing the revs to "slightly" above idle.

(ii) More serious heavier cluncking noises; Again your hose to the ear
will tell you it's originating below the very top of the engine, it will
probably be localised & it's rate will probably be quite fast. With the
hose you'll at least know which side & end of the engine is the cause.
Then leaving the engine idling, try pulling the spark leads off the
plugs in the suspect area one at a time, till the noise stops (even a
bad thing, given you have oil pressure will be quiet when the plug stops
firing above it). This is now potentially serious so get a compression
tester from an auto parts store (a really cheap one is fine).

(iii) Follow the testers instructions but generally take all the plugs
out, disable the ignition, leave or manually hold the throttle wide open
& crank the engine with the tester in each cyl in turn. Note (as in
write down:-)) the pressures for each cyl. Don't worry about the actual
numbers (particularly with a cheap tester), what you're looking for is a
consistent reading over all the cyls, no more than say a 10% difference
between the highest & lowest. If you get one or an adjacent pair with
very low readings & that/they are the ones you found were causing the
noise, sorry you need to at the very least take that head but better
both heads off & find out what's going on.

K