HELP! - unknown fuel leak 1994 40hp

Hello,

I am the owner of a motorboat "Skibsplast Sportsmann 14" (made in Norway) with a Johnson 40HP outboard (BJ40 BAER, 1994).

I have detected a fuel leak but I don't understand what's happen!?
When I sail, the boat and motor are OK, everything is working.

When my motorboat is moored (and quiet), that's OK.
But when the boat is moved (for example to go on board), a fuel spot (fuel smells) appears on the water, around the motor!

I have tried to see if something was not OK around the motor but I can't see anything (any fuel leak!)!?
I have disconnected the fuel but no change!
It seems that the fuel comes from under water....

Thanks for any help
Sylvain

Re: HELP! - unknown fuel leak

It's quite possible that no fuel leak exists.

The fuel/oil mixture will over a period of time drain down thru the long exhaust housing.... the housing between the powerhead and the lower unit. This mixture will of course be sitting on top of the water that is within that long housing, unable to drain any further down.

The sudden movement of the boat, as when one moves from the dock onto the craft, would naturally distrub that level of water an cause some of it to escape outside of the engine.

This may not be the cause of the problem but it is a strong possibility.

Re: HELP! - unknown fuel leak

Hello, thanks for your answer!

That means all the outboard motorboat have the same thing and that's a normal thing?!?

I have never seen such thing in other motorboats.
And a "lot of" fuel escapes outside... (ok, not much but there is a fuel smells and pollution). I imagine if all the motorboats have the same escape...

Can you tell me why the mixture drain down thru the exhaust housing?

Thanks
Sylvain

Re: HELP! - unknown fuel leak

The fuel is never completely burnt off in the combustion chambers due to the oil content mixture needed for lubrication. This excess simply drains down from the powerhead. Many of the late model engines now have recirculating valves which helps with this common problem by moving the excess mixture from one cylinder to another in an attempt to burn it off..... it helps but still some remains.

If this condition you experience does not happen with any other craft in your area that is similar in design (I assume sailboat, outboard auxiliary), then I would suspect that perhaps a fuel pump or carburetor problem exists...... ruptured fuel pump diaphragm, carburetor float level set wrong, something of this nature that would allow more than a normal amount of fuel mixture drain down thru that housing.

Re: HELP! - unknown fuel leak

>If this condition you experience does not happen with any other craft in your area that is similar in design (I assume sailboat, outboard auxiliary)
Yes, I think that's the case (if not, all the area should smell fuel...).

if someone has experimented a similar problem in a Johnson outboard motor, please let me know!

Thanks