HarryNH Loc: Amherst NH

Hi folks. I thought I'd share an adventure I have been having with my old 1974 Mercury 402 outboard. I live way up north in Amherst NH, and am the proud owner of my grandfathers old Terry Bass boat, which came with a 1974 Mercury 402 outboard. I became the custodian of "family" boat about 10 years ago and I look at it as an honor to keep the memory of my grandfather alive. However, I am finding it becoming more and more of a challenge to get the motor running in the spring. Usually I need to clean and rebuild the carburetor. However, this year has been a classic. It started off kinda like it usually does with the motor running rough, but then the motor got to where it barely would idle. And then if it was running, it would suddenly just die and refuse to restart until it decided it was ready.

So, I took it to a friend of mine who loves working on old motors and stuff and after messing with it for a day, we finally decided to clean the carb again so we took it apart and found water in the bowl. That was a surprise, but we cleaned the carb and then turned our attention to where did the water come from. The first place we looked was the fuel tank that was connected to the motor. We drained it, looked at the gas (which was Hi-Test and a week old) and no water. Then, we looked at the other tank of gas from last year, and found about a quart of water in bottom of the tank. Where the water came from, I have no idea. But, I had started off using that tank for the first motor run as usual so that was the source of the water. So, we were very careful to try to flush everything in the fuel system that may have been contaminated. The fuel line was flushed with air, and it had water in it. After that was clean, we fired the motor up again and the same thing was still happening - it would run and then just die. So, we pulled the plugs and they had water on them. Then we took one of those inspection cameras and looked inside the cylinders and saw the evidence of water on the rings so we assumed that we had water in the crank case, which made sense. So now, the problem became how do you get the water out of the crank case.

When I got the boat and motor, I bought a copy of the Mercury 402 manual on-line and kept a copy of it. The manual contained a discussion of what to do if your motor gets submerged. what the book said was to remove the motor from the boat, pull the plugs, put the motor in the horizontal position, plug side facing down, and them manually rotate the motor with a wrench for about 10 revolutions to purge as much water as possible. Once that has been done, pour a good amount of alcohol down the carburetor throat (alcohol absorbs water), and then manually spin the motor a couple of revolutions to pump the alcohol through the system. And then, pour motor oil into the carburetor and then manually spin the motor again. Once you have done all of this, put the motor back on the boat and see if it will start. If so, start the motor and run it for about an hour just to make sure all of the water has been purged from the motor. so, we did all of that today and the motor started and seems to be running about as it should. Now I am going to take the boat to the lake on Monday and run it around the lake for a while and purge the last of the motor, and finally I can go fishing. Morale of the story, don't get cheap by trying to use last years left over gas. I put stabilizer in the gas, Sea Foam, some Mercury enzyme gas treatment, and all of that stuff. From now on, last years gas gets tossed and I'm starting out fresh.

E.pa.al Loc: Martin's Creek

Hope you got it figured out Harry,good luck

Fredfish Loc: Prospect CT.

Harry, I have a question, was it a metal tank or plastic? Metal tanks get condensation in them if not full. The corn liquor in the gas these days attracts water as well. My 1990 25 has a bowl type filter housing, which will trap any water before it gets to the carb. In the last 11 or so years, I've never found any water in the filter bowl, and I keep the 15 gallon plastic tank about 3/4 full during the winter. For the last 6 or 7 yrs,the only additive I use is Startron Marine formula, and I use it year round. Good luck buddy, I hope she purrs like a kitten for you.

Gordon Loc: Charleston South Carolina

Good post Harry. From that year I would say it's a 2 stroke engine. Where you have an oil ejector or you mix the oil in the tank. My boat has a 130 gal. Tank and every winter I pump the gas out and run it in my truck. And yes. I pay for the gas as I use it so I have the money to fill it in the spring. If you don't mix yours in the tank. Burn it on your truck. Just saying.

Fredfish Loc: Prospect CT.

Harry's is way before oil injection G. That didn't start till the mid '80s. In fact his is probably a 20:1 oil ratio, like my 1971 135hp. My 1990 25hp is 50:1 but its still pre-mix.

Barnacles Loc: Northern California

Good post, Harry.
I had a 1975 Mercury (85HP) and the manual called for 50:1 on that engine.
Get a water separating fuel filter! It's a good investment. And if you can find pure gas (no ethanol), you'll have WAY fewer headaches.

Jeremy Loc: America

YUP

Jeremy Loc: America

Use non ethanol if possible. Always run carbs out of fuel if possible for winter. Flush fuel tank and only have non ethanol on its last run of the year in fall. People say fuel is spendy Non ethanol was 5 bucks now it’s 6 so it’s actually cheaper than others. Alcohol has a consistent octane that’s why race boats and cars run it.

HarryNH Loc: Amherst NH

Thanks dudes. Barnacles suggestion about installing a water filter in the fuel line makes a lot of sense; especially considering the learning exercise I've been going through. I'll keep everyone posted. Enjoy your weekend.

Fishing Fool Loc: redding, ca

I also add a can of lead treatment per 25 gallons of gas and my older motors put like kittens. I also add the Amsoil gasoline treatment to my 300 gallon fuel tank. Great idea to have inline fuel filter to filter out water and sediments.

agatemaggot Loc: iowa

When done for the season, don't toss the remaining gas, put it in the tow vehicle and use it up !

Barnacles Loc: Northern California

Something I forgot to say about water separating fuel filters: A lot of them just look like a spin-on oil filter like the cars use. I chose one that has a drain, so I can drain just a bit into a cup and look at it to see if there's water. If so, you can address the issue before it becomes a problem.

Fredfish Loc: Prospect CT.

Racor makes a nice one, with a clear bottom and drain petcock.

Walmart has the best price

HarryNH Loc: Amherst NH

I like that. Thanks Fred and Barnacles.

Gordon Loc: Charleston South Carolina

That's the one I have Fred. Works great