Need Help WithA Mercury 3.3 Outboard

[Joe Mullee]

My 1999 Mercury 3.3 outboard doesn't get a lot of use, probably about ten times a year. Lately when I have gone to start it I had a hard time getting it running and then had a hard time keeping it running as I open the choke. I do the "manual" maintainance on it every winter. Admittedly the fuel in the tank was from last year.

The reason I ask is that when it does get going and after it warms up, if I do open the choke, even a little bit, it starts to lose power and eventually quits within a few seconds. This happens even after 20 minutes of continuous operation. Choke completely closed = it runs seemingly without problems. Choke opened after a few minutes (even a little bit) = she dies within a few seconds.

The manual says the choke should remain closed to start a cold engine but should be opened after the engine warms up. Any idea's on why this is happening?

Thanks,
Joe Mullee

 

[Sailm8]

Old gas and needs a carb cleaning. They gum up very quickly with ethanol gas. Easy to do yourself.

 

[Rich Stidger]

I've had running issues with my Nissan 3.5 and it is basically the same engine as you have.

Advice that I have received and has worked for me is:

Remove the carb, completely disassemble, and soak everything (except gaskets) in a carb dip cleaner for four hours. Then spray through all passages with spray carb cleaner. I even ran pipe cleaners through the larger passages.

Reassemble carb and replace on engine. Remove and drain the fuel tank and clean it out with some of the carb dip cleaner. Clean or replace any fuel filter- mine has a screen in the fuel petcock.

Buy new fuel- use hi-test and add a dose of Marine Sta-Bil right from the get-go. Be sure that you have the proper amount of 2-cycle oil and that it is the correct type of oil. Too much oil will cause bad running.

Replace the plug. You should now have a good running outboard unless you are closely related to Mr. Murphy.

 

[JoeWhite]

After you complete the cleaning - when you are ready to leave the boat - run the engine with the fuel line disconnected so that all the fuel is used up that is in the carburetor. This is what I did and I never had any problem.

 

[petersea]

Got to love that ethanol ! OK here is the (hopefully) first step before you remove carb. Try some spray carb cleaner into mouth of carb AFTER you get rid of the old gas replace with fresh gas that has been treated with gas stabilizer (several brands on market but suggest marine sta-bil) and some more carb cleaner in new gas (gum out). this may work for you since the engine is still running with choke on. Next suggestion is to purchase small (one gallon at a time) quantities of gas and use the engine on regular basis. If this does not work do as other suggested and remove and bench clean carb. Still recommend using only treated fuel is small amounts. Better yet if aviation fuel is available or non ethanol fuel is available in your area use that but still treat it.

 

[higgs]

You MUST run the carb dry before storing for the winter.

 

[Doc_holiday]

You MUST run the carb dry before storing for the winter.

I do this every time I shut it down for the day. It's amazing how long the motor will run at idle with no gas line attached. Seems it may run 2 minutes.

 

[Tom G P-21]

Clean the carb first as mentioned earlier. For maintenance, others have recommended running the carb dry when you are done using it for the day. Also, I believe your model has a drain at the bottom of the carb bowl, look for a small screw at the bottom of the bowl. When you are winterizing it, ie fogging it, also drain the carb bowl. Even when you run it till it stops there is still a residual amount left in the carb that can cause problems.

 

[Crazy Dave Condon]

AS a former small boat dealer for many years, I always advised the following on small engines and your Mercury is probably built by Tohatsu as is the Nissan and others in the past.

1. Always allow the engine to run out of fuel no matter if straight or ethanol mixed.
Gas is an oil by product and it will coagulate and clog the fine jets in your carb if allowed to stand in the carb bowel.

2. If ethanol, add the inhibitors as it helps.

3. At the end of the season, always drain all gas from the engine and/or gas tank.

Good advice my friend.

crazy dave condon

 

[richk]

I just ended what I hope is an at least 5 year struggle with trying to get and keep my 3.5 hp Nissan (Tohatsu) 2 stroke running. I think I won, but ask me again at the end of this summer. Here's what I did

Buy a carb rebuild kit (Defender's got em)
Have a backyard, respected, small engine repair guy rebuild the carb
By aviation gas at a local airport (cost me $6/gal) no ethanol
Learn how to start the engine again (apparently AvGas and my engine behave differently together.)

Live happily every after.

 

[tomgrigsby]

I do this every time I shut it down for the day. It's amazing how long the motor will run at idle with no gas line attached. Seems it may run 2 minutes.

X3. Ran my Evinrude Fisherman dry after every outing. In 10 years it always started and ran fine even over the course of infrequent use

Also agree with other posters, disassemble and clean the carb. An old guitar string (.010) works well for poking through very small passages.

 

[Benny17441]

I keep the practice of shutting off the fuel valve and allowing the engine to run dry but even then it only helps if you use the engine frequently. There is no substitute for removing the carburator and cleaning the gum out of it. In extreme cases replcing the carburator is the only solution. Try some additives but try to start it every so often and let it run for a few minutes. Ill stick it into a garbage pail full of water and run it. I also have a 5HP Nissan and a Honda generator to maintain.

 

[Gunni]

Time to learn how to strip and clean your carburetor. It gets easy after the 12th time. :neutral: The jets are clogged with all that stuff that corroded off the inside of your float bowl after water accumulated there. Make sure you scrub the bowl real well, and blow out the jets. A pipe cleaner and sewing needle help. Don't get too aggressive, they are finely calibrated passages.

Store no more gas than you can use in 90 days. Always keep your vent cap shut when not in use. Star Tron makes a superior gas treatment. High Octane premium gas can cause unnecessary carbon buildup. Observe owners manual specification for octane rating. Strip and cleaning carburetors has joined the impeller replacement on the yearly maintenance list.