Gas odor with small slick behind boat.

[Sickday]

First let me say these forums have been extremely helpful in my previous boat repairs! Starter, water pump, ujoints, gimbal bearing and both bellows.

New problem: 87' merc 3.0 140hp.

I took my boat out yesterday and I noticed a little gas slick in the water behind my boat while idling in place. I could also detect a gas odor. While pulling a tuber, he also said he could faintly smell gas behind my boat.

The boat idles a little rough but runs great out of the hole and at WOT. No hesitations, misses or anything. It does seem to be on the poor gas mileage side for an engine this size. Is it possible the carb is just running rich or ???

I will be pulling the plugs today to check their condition as a start. Where to next?

 

[sea wolf]

Re: Gas odor with small slick behind boat.

Find out what's going on & don't run the boat until you do before you blow yourself to smithereens. The gas fumes are one thing, but are you sure you're not leaking gear oil?

 

[Sickday]

Re: Gas odor with small slick behind boat.

It is possible it could be left over gear oil in the lower unit....? The lower unit was leaking a bit of oil out of the water weep hole due to a bad quad seal, which I fixed last week when I also did the water pump rebuild.

I am checking the lines next but I am not expecting to find a leak. There has never been a drop of gas or oil in the bottom of the hull.

And I do not plan on taking it out until I solve my problem.

 

[cr2k]

Re: Gas odor with small slick behind boat.

OK you have possibly solved the oil slick problem...

How faint is the gas smell? Is it inside or outside near the back of the boat?
If the later you are probably smelling vapors from the fuel tank vent.

 

[Glastron_V210]

Re: Gas odor with small slick behind boat.

The tilt/trim lines can also deteriorate and leak oil and show up 'slick like'.

As for the fuel, find it asap (No kidding, eh?). Ok, not so helpfull. But check the regular fittings, fuel pump, tank etc.

Chay

 

[Sickday]

Re: Gas odor with small slick behind boat.

cr2k, the odor is more prominent after idling for 3 minutes with the blower on. I read through a carb post on here relating to ethanol gas and hard starts after warmed up, which a solution was to run at idle for 3 minutes before shutting it down. It seemed to work as my boat fired right up without dropping it into neutral and giving it a little gas.

The odor is located at the stern-inside and in my opinion too strong of an odor, at least to my likings

OMW out to check the fittings and lines.

 

[rbh]

Re: Gas odor with small slick behind boat.

if you flood the engine I gaurantee you will smell and see gas, if your float is sticking thats another possibility.
and if your running really rich that will leave a nice rainbow behind your boat and smell as well.
Rob