1997 Mercury 9.9 Outboard water leak - picture says it all

I have a little 9.9 I use with the kids now and again and the last time I had it out it was sputtering and made a horrible sound and shut off. It fired right up again and ran fine for the rest of the ride, but when I slowed down coming in to shore it started sputtering and shut off. I thought it might be bad gas so I dumped the gas and got fresh gas and oil mixed at 40:1. It fired right up and I proceeded to drive it but it started smoking and shut off. I noticed water dripping out of the cowl and thought that was strange, so I pulled the cowl and started it and found there is water shooting out from a gasket on the port side of the motor. Is this just a matter of replacing the gasket? common problem? I have never seen an outboard apart so the orientation of the motor is kind of strange to me.

Re: 1997 Mercury 9.9 Outboard water leak - picture says it all

The cylinder exhaust ports are right under that cover. They put out hot exhaust gasses so there is usually a sealed alum plate a water jacket (filled with water directly from the impeller...under a few # of water pump pressure.... to keep the cover cool) and a sealed cover.

Yes on the gasket leaking but if you had engine problems to boot, one has to ask the question as to why. If the plate and plate to block interface seal is intact and no water got past that seal into the output ports of the engine then I can only surmise that enough water squirted out in the correct direction to be picked up (mist maybe) by the carb venturi and upon ingesting water the engine started it's erratic behavior.

HTH,
Mark

Re: 1997 Mercury 9.9 Outboard water leak - picture says it all

Thanks, I suspect it is just as you say, that the water or mist was being ingested by the carb. The foam all around the cowling was soaking wet and in the picture you can see the water it hitting the starter wheel and shooting out from it. I looked at the microfiche it appears there are two gaskets, one on either side of the aluminum plate you mentioned. The gaskets appear to be pretty cheap in price, I think I will just replace both gaskets and see how it runs. Just wondering what would have caused that to happen?

Re: 1997 Mercury 9.9 Outboard water leak - picture says it all

rjd75 said:

Thanks, I suspect it is just as you say, that the water or mist was being ingested by the carb. The foam all around the cowling was soaking wet and in the picture you can see the water it hitting the starter wheel and shooting out from it. I looked at the microfiche it appears there are two gaskets, one on either side of the aluminum plate you mentioned. The gaskets appear to be pretty cheap in price, I think I will just replace both gaskets and see how it runs. Just wondering what would have caused that to happen?

Click to expand...

Age. Not all that uncommon.


When you go to replace it, clean up your alum surfaces that mate to it. In my experience, the alum that mates to the gasket is just raw cast alum and over time it corrodes which is incapable of resisting the 3-10# of water pressure the impeller can pump.

The bolts are sometimes hard to get out. If so, a penetrating oil and impact is the best way to get them out without breaking them off......course on a '97 it shouldn't be that bad. Impact could be as simple as a boxed end wrench that you strike repeatedly with a hammer. This process will loosen bolts that a constant twisting motion sometimes will just bend them till they break-off.

Clean the threads of your bolts prior to installing and if you have a suitable tap, chasing the threads in the block wouldn't hurt either. Also you might put something on them to prevent them from seizing in the future. Blue Locktite brand thread sealant is a good choice from your auto parts store. Torque specs are on www. If the top of the bolt has 3 marks 120 degrees apart it is a grade 5 SS.

Mark

Re: 1997 Mercury 9.9 Outboard water leak - picture says it all

Ok, thanks for all of the advice! Hopefully that is it and it's a simple fix. I will report back when I have it done and tested.