Mercury Boating - Recent Questions, Troubleshooting & Support


Best not to do it as you will get maybe 2 mph. Also, I believe it is ******* to modify 1996 and later motors.

Mercury Boating | Answered on Sep 09, 2019


That cylinder isn't firing. Bad plug, or no spark to that cylinder. Swap the plug to another cylinder and check again. Then swap the coil to another cylinder.

Mercury Boating | Answered on Aug 22, 2019


Wow, a 40hp is FAR too small for a 16 foot anything except a bare aluminum Jon Boat with one person and a tank of gas!

90 to 110 hp is the recommended. I was guessing 70 to 90.
https://www.crestliner.com/fish-hawk/1650-fish-hawk

http://www.marineengine.com/boat-forum/showthread.php?289110-1999-mercury-40-2-stroke

WOT is normally 5000 to 5,500 WOT, but yours is struggling with the weight. There should be a coastguard regulation sticker in the boat with the Max HP that hull can take. You should have that motor or 10hp less.

The manual indicates 5,000 rpm for timing.

https://www.manualslib.com/manual/1198862/Mercury-40.html?page=9#manual

Mercury Boating | Answered on Jul 24, 2019


If you know the year or model number, you should be able to find the diagrams at http://www.crowleymarine.com. Otherwise call, I've known them to be really helpful.

Mercury Boating | Answered on Jul 12, 2019


Any outboard 2 cycle after 1965 will run on 50:1 approx 500ml or half a quart per 5 gallon tank.

Mercury Boating | Answered on Jul 06, 2019


Check the fuel filter for blockage and check the plugs for spark. If no spark, you could have bad coils. Here is a video on how to go through the checks.

Mercury Boating | Answered on Jul 06, 2019


Low oil alarm. They do suffer with a faulty low level alarm switch. Details in the link with some good videos

https://www.google.com/search?q=1991+75hp+outboard+has+a+constant+beep+alarm

Mercury Boating | Answered on Jun 24, 2019


(Carburetor Adjustment - Single S/S Adjustable Needle Valve)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Mercury Boating | Answered on Jun 19, 2019


Sounds like the gas isn't flowing freely into the carb. Check to see if the gas lines are open, no obstructions. Also check the gas tank, I there is a screen on the gas inlet tube and that might be plugged.

Mercury Boating | Answered on Jun 16, 2019


There are some universal ones available, but I just stick my 9hp outboard in a bucket of water and flush that way.

Mercury Boating | Answered on Jun 11, 2019


Product Line Year H.P. Model Number Model Description MERCURY 1986 45 1045776 45/50 HP

Mercury Boating | Answered on Jun 09, 2019


Looks like this;
Product Line Year H.P. Model Number Model Description MERCURY 1985 7.5 1007205 7.5 /9.8 H.P.

Mercury Mark 75... | Answered on Jun 09, 2019


Product Line Year H.P. Model Number Model Description MERCURY 1983 25 1025523 MERC 25

Mercury Boating | Answered on Jun 09, 2019


Depends entirely on the type and horsepower!

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Mercury Outboard Serial Number Guide

Mercury Boating | Answered on Jun 09, 2019

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