I just got use of one that is 10 years old and never run before. Runs good and quiet. I now have two hours on it, no full speed just normal up and down the throttle from idle to 3/4 throttle. But not easy to start. And definately not on the first pull. I have to use the choke on every start no matter how warm the engine is and even have to pump the primer bulb several times and still will not start o the first pull. Some times it takes quite afew pulls to get going. Is this normal or is it just this engine? or is it me? Thanks ahead for all the info you can give. Ps it has a new impeller and it is heavier than my old (1977) 15 johnson......jk

Check the Spark Plug??
Might need a carb cleaning if its not fuel injected. Ethanol is hard on carbs.

bout sounds like an air leak

I have one almost the same age I never use the choke and I mean never, just pump primer bulb and push throttle button on left side of motor and turn the throttle up and start. Mine is very sensitive to a dirty carburetor so run all the gas out of the carburetor when you are done using it for a long length of time.

Mine will only run good on high octane gas.

What does the high octane do to make it run better, or, what is the reason it runs better on high octane?

Before you do any work on the engine try this.
Replace the complete fuel line - connectors, bulb, and hose. Simply buy a new fuel line with the correct connectors.
Also add some Seafoam to every tank of gas for the rest of its life, it preserves the fuel and cleans the system.
And if you can find it, run only real gasoline with no alcohol.

After doing these maintenance issues, you may need to adjust the carburetor.

That engine should run like new.

^^^^^^^^^^
Good advice right there.

The 4 strokers are a lot heavier than the old two strokers. The torque range is a little different too, but the quietness and lack of fumes is great!

jk,
Your experience with that motor is typical of every Mercury outboard I ever used. Hard to start or inconsistent starting. I was stranded by one many years ago and promised myself I would never own a Mercury outboard under any circumstance. I have advised friends not to buy them. They all ignored my advice-- and all came to the same conclusion the hard way. All of them were 2 cycle motors though. I would think the newer 4 cycles would be better.I've talked to many people who say they have had nothing but excellent service from mercury motors. To be fair, they may have greatly improved since I've pulled one of their starter ropes while scrolling through my entire list of 4 letter words.
That promise I made will not be broken.

This is what I would do. You can interchange the seafoam for startron or stabil(blue), but I'm sure all work well. I would not, and Mercury would not, recommend using high octane as it has extra ethanol in it. The manual says 87 octane.

Kyt - sorry the black engines are not good for you. I absolutely believe you, but it is really amazing how that works back and forth. What outboards have worked well for you?

I have had great success with Merc for 35 years and rely on them to get me back when it really counts. So far, I have never used one of their new 4 stroke outboards. My favorite Merc is a tiller model 2001 “Classic 50” 2 cycle 50hp with hydraulic trim and tilt. I am looking for a new used Sea Ray boat right now. For me to consider a boat, it must have Merc twin inboards making a total of 680hp.

I'm guessing a ten year old four stroke is carbureted. The fact that it only throttles up to 3/4 make me think there is a high-speed jet that's plugged, the other symptoms would make me think there are other carb issues as well.

I'll bet the engine was run 10 years ago and put away with some gas in the system. Take a float bowl off and I'll bet you'll see some green varnish in it. Sounds like a carb kit may be needed and some real carb cleaner (not the aerosol kind). Someone mentioned vacuum leaks also, good idea to check all potenial leak points (carb boots/gaskets, etc).

My 35 Merc is 34 yrs old and is no problem use stabil or seafoam year round

Waggler - I agree with you but wanted him to try my suggestions first which he should do anyhow.

If it has a carb, and since it does run, the seafoam in a double or triple dose should dissolve the crud and cleanup the carb. It is worth a try. Your idea of a carb rebuild is excellent, but most guys won’t try that.

waggler the only reason I did not use a higher throttle setting is that is was only run for about an hour long time ago. The engine has more throttle in it that I did not use, I was trying to break it in. Willy Firewood, excellent idea, I should have thought of that. One new hose coming up. I do use the blue Staybil in all my engines now and the red over winter(or summer for the snow blower) I am a firm beliver in that stuff. And we cleaned the carb and put new plugs into it. It runs real nice once started and I will not be carrying it into the woods in Canada. I am to old for that much weight, I have an old 6 hp Johnson, first pull zoom. the new fuel line is my next purchase traprjohn, I agree with you Matt28, do you have to prime it with the bulb even when it is warm, just run a second earlier? I am not used to that. Willy Firewood, I just looked and my fuel line is perminately attached to the tank. Not a snap on connection like at the other end, is yours the same? Will have a new line soon.
Everyone, up in Canada where we go, Chibagamau area, 25 years ago the locals did not like the black motors but since then they are now very common. I just liked the idea of a 4 cycle thinking that there would be no chance of fowled plugs(no oil in the gas) easier starting and quieter and slower running. Wsell yes on the last two but it is to heavy to take to Canada to carry any distance.....Thanks for all the replys......jk

Hi JK,

It sounds like you have a good handle on that engine situation. You must have made a good find with only one hour of use.

I have never used or owned a 4 cycle outboard simply because of the weight. I have never been concerned about any of my outboards fouling any water. They are in excellent condition with preventative maintenance. I do not want to be stranded in the wilderness, anywhere really. I always use Merc 2 cycle oil which has almost no smoke.

I would not tolerate a hose permanently attached to a tank, but that is personal preference. You can adapt the hose or the tank as desired. Get the correct diameter for the tank hose barb, cut off the connector from the hose and use a hose clamp. May need to change the barb to fit the hose you buy. Or install a connecter onto the tank.

Best wishes.