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Author Topic:   Gas Sheen on the Water (leak?)
Morocco posted 09-12-2002 05:14 PM ET (US)   Profile for Morocco   Send Email to Morocco  
I've noticed that my starboard engine seems to be leaking a miniscule amount of gas -- by miniscule, I mean that when I lower the engine I get a rainbow 'sheen' as the 'upper lower' unit hits the water.

The engine runs fine through all ranges, but every wave at anchor seems to 'wash' a little sheen of gas into the water.

The other engine doesn't do this at all. I've had the cowl off, but can't seem to find any visible place that is leaking. (And I've held my bic lighter REALLY close to illuminate the situation...)

Mechanic says it ain't broke enough to fix, but I thought I'd see if anyone has had something like this, and maybe what to expect.

In medicine we call this the differential diagnosis -- all the things, in order from most to least likely -- for a symptom.

I hate to pollute, even a quarter teaspoon at a time.

David Ratusnik posted 09-12-2002 05:39 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Carb. Do you tilt the engine up fully?

These older engines leak abit period. I lose enough trim/tilt fluid over 6 months that the mechanism starts to act up and say- fill up the resevoir. It must go into the water.

Also, the trim tabs may give up a small quantity of fluid over time- only into the water. kResevoir seems fine.

Until you buy a green machine engine I sort of agree with your mechanic- don't shoot yourself in the foot if it's running sweet.

.03 David

etstmeb posted 09-12-2002 08:40 PM ET (US)     Profile for etstmeb  Send Email to etstmeb     
Most likely a lower unit leak. Check the O rings on the filler and drain screws.
triblet posted 09-13-2002 01:09 AM ET (US)     Profile for triblet  Send Email to triblet     
I'm thinking lower unit lube too, not gas.
and WAY less than a half teaspoon. One
drop will cause a huge sheen.

First thing I'd do is change the lower unit
lube on the starboard side and see if there's
water in the oil.

I had a buddy who bought a used inflatable.
It put a small sheen on the water. And lets
lots of water into the lower unit lube.

At least on my Evinrude, the lower unit plugs
have flat gaskets, not O-rings.


tocobill posted 09-15-2002 11:29 PM ET (US)     Profile for tocobill  Send Email to tocobill     
What year and brand motor do you have?
Morocco posted 09-16-2002 01:20 PM ET (US)     Profile for Morocco  Send Email to Morocco     
1987 Johnson 150 GT, times two...
keltonkrew posted 09-16-2002 03:06 PM ET (US)     Profile for keltonkrew  Send Email to keltonkrew     
My Merc 35 was doing this. turned out to be the diaphram in the fuel pump was going out.
Bigshot posted 09-16-2002 03:31 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
probably gas. When you tilt some dribbles into the flame arrestor. When you lower engine it trckles down and out of the cowling. Could also be trim fluid but gas is my guess. I highly doubt lower unit. If that was leaking it would drip into the water while tilted.
David Ratusnik posted 09-16-2002 03:47 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
"Sheen" is gas. D
bob1008 posted 09-17-2002 07:10 AM ET (US)     Profile for bob1008  Send Email to bob1008     
I have the exact same set of motors (87' 150's) and had the exact same problem with the starboard engine. This model has a fuel recirculation system that tries to burn unused fuel a 'second time around". These are (6) very very thin fuel lines, (2) just under each carb that plug into a brass check valve fitting. Run the motor and look very very closely with a flashlight under each carb. One of mine was broken off completely and spraying a fine mist of fuel.
Morocco posted 09-17-2002 05:52 PM ET (US)     Profile for Morocco  Send Email to Morocco     
Thanks all for the replies -- I've checked the lower units and it looks okay, so I think bigshot has the most plausable diagnosis -- I was wondering why I wasn't getting a drip off the lowest point when I tilted the engines -- I'm gonna go check those fuel recirculation lines today.

Dang, another reason to have to drag myself down to the boat. And dang it, I might just have to take it out for a few minutes, just to double check.


keltonkrew posted 09-17-2002 07:33 PM ET (US)     Profile for keltonkrew  Send Email to keltonkrew     
You ALWAYS have to take it out to test. You can't see the "sheen" in storage!!!!!

Take your fishing poles. Never know how long you have to check it. Some need to be checked over and over again to gain confidence the problem is fixed!

David Ratusnik posted 09-17-2002 07:37 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Bet it checks out fine.

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