HELP! My small outboard is way to finicky. 2007 4 hp

I bought a used 2007 4HP, 4 stroke Merc outboard with integral gas tank, connection for external gas tank and F/N/R. It's exactly what I was looking for for my 21' sailboat. However I can't seem to get it to start and run reliably. A friend traced the gas line, cleaned the petcock filter & carburator and it ran fine... for a while. I took it to a repair shop and had it checked out. They said the gas was bad, replaced it and the spark plug. Again, it ran fine... for a while. I returned to the repair shop and was given a lecture about bad gas. The tank was refilled and the mechanic had the motor running again. Back on the stern of my boat it... well you know the story. The motor looks to be in excellent condition. What can I do to make this motor be my old reliable outboard that I love? Thanks for any help you may offer.

Re: HELP! My small outboard is way to finicky.

"What can I do to make this motor be my old reliable outboard that I love?" - simple answer, Sell It and get a 2 stroke or move up to a twin cylinder 4 stroke.

Ok, joking aside, this is a single cylinder 4 stroke - so a single powerstroke has to carry the flywheel, crank, shaft's etc 720 degrees before the plug fires again - not ideal and can result in a "shaky" idle at the best of times (they run real nice until the "new" wears off).

These little Mercs (4, 5 and 6 horse) which are 100% built by Tohatsu (the only difference between Tohatsu, Nissan and Mercury in this model line is the paint and decals on the cowl) have significant owner complaints, with the leading one being "they run like crap".

Since you have had the fuel system "tuned up" the only other "mechanical" suggestion I have is to have the valves adjusted - once in the life of these motors is often enough and is recommended at the 3 year OR 300 hour mark, whichever comes first.

Then ALWAYS run fresh, stablized gas - every time out - gas more than 2 days old is too old for some of these motors, they are that picky. Take the extra step of draining the carb if the motor won't be used until "next weekend".

If that sounds like alot of extra work then I welcome you to the single cylinder, 4 stroke owners club - you aren't alone...

Thanks. I appreciate the lengthy reply even though it has me thinking of selling the engine. I mistakenly thought 4 cycles were more reliable than 2 cycles. That's not the case, huh?

i'm loving my four stroke briggs. pull the handle and it lurches into action.

It's really tough to give a simple answer as whether one is better than the other. A two stroke will stand for alot of neglect and abuse and still fire up just about every time - never change the plugs, it fires - never winterize it, it may still fire - leave in the shed for 10 years, haul it out, hook up a tank a gas and away she goes. Does that make it more reliable or just more tollerant?

Now think of your car/truck - it's start in just about any weather condition you throw at it - never clogs a fuel line or back fires or any of the thousand other things that many outboards do. So why doesn't your 4 stroke outboard work in the same trouble free fashion.

That does get asked alot and to explain it I use a story (author unknown or I would give the credit).

Try this some time. Park your car in the driveway at the end of September with the hood open and no special prep - whatever gas is in the tank, just leave it there. Leave the car sitting there until the following May or June and then on one nice sunny weekend close the hood and start it up (you may need a boost). Once it's running immediately put it in gear but don't touch the gas until you absolutely have to, to get the car rolling.

Let it roll down the street at idle speed - if you have to touch the gas a bit to keep her running, that's ok, but DO NOT exceed 5 mph. Run her this way down to the closest freeway on ramp. Once you turn onto the ramp put the pedal to the floor and keep it there for 30 mintues - then pull the car to the side of the road, turn it off for an hour, then start it up and reverse the process until it's back in your driveway. Leave it parked once again for 2-4 weeks and repeat the process.

Now how long would you expect the engine in your car to last.

Sound rediculous - that's how we treat our outboards. A 2 stroke doesn't seem to mind, a 4 stroke does very much...

I am so over small two strokes. Every single one of mine from weed whacker to chainsaw to outboard died within a month of ingesting ethanol.

I have seen the smaller 4 stroke mercs that run poorly and helped diagnose the problem. We (friend and I) discovered that the exhaust tends to clog up with crap. Now when we encounter a poor running small 4 stroke we always check the exhaust and end up wire brushing the entire leg out.

It will only cost you some time to check it and it might be worth it. IMO a 4 hp on a 21' sailboat is asking allot.

I started running E-10 (10% ethanol) about 10 years ago in my outboards (the newest one is a 1991, the others all from the mid-80's). Two seasons back 89 octane E-15 became available. It sells for the same price as 86 octane E-10 at a local gas station. Since the EPA was already looking at the approval process for widespread E-15 sales (and Canada usually always keeps gas trends in-line with the US), I decided to run it to see if all the doom/gloom prophet's were right.

Well, after now at least 10 seasons of ethanol enhanced gas - maybe 8 years of E-10 and two years of E-15, what problems have my outboards experienced?

Nothing, nada, not a single failure to start - not a single clogged carb - no vanishing hoses/lines/seals - nothing.

I live in climate that see's drastic temperature swings which can lead to condensation issues in the gas tank yet only one of my motors is equipped with a water separating filter (my 140 horse). My 2.5 horse (twin), my 9.9's and my 15 all get their gas straight from the portable tank. A couple of the motors see about 100 hours run time a year, the others vary between a few and maybe 20 hours a year.

The only thing I have done "special" is ensure that I always run fresh, stablized gas - so fresh gas each week (leftover goes in my pick-up truck which doesn't even mind the 50:1 mix which is more like 300 or 500:1 by time it mixes with what's already in the tank or I burn the leftover in the lawnmower) and a capful of stablizer.

So either my 20-30 year old 2 stroke engines are blessed/lucky or the big old Ethanol "boogie-man" is afraid of me personally

Or maybe I have just adapted to running ethanol blend with a bit of stabil - seems to work fine - and since ethanol is here to stay, at least for the near future, and the trend is getting to be higher percentages, not lower, the sooner we stop blaming it and just adjust, the happier our engine (and us) will be.

Without ethanol whatever would we blame our lack of maintenance on when the motor gives us trouble??? Unleaded fuel?? - no wait, that was the excuse 30 years ago....

Galamb, my chainsaw was 6months old when it got it's first taste of gasahol. All of the gas lines and primer bulb disintegrated. My 8 year old weed whack did the same thing. The repair shop said that the carb had to be replaced because it got all gummed up with stuff that gasahol dissolved. It went about a month before the filler cap started leaking because the seal was disolved - and - it needed another cabrerator. So I threw it away and bought a brand new Ryobi weed whacker for cheap. It overheated and died the second time I used it. Turns out that gasahol burns hotter than gas.

Meanwhile, my four stroke lawnmower still keeps going. Starts on first pull. Actually, they both still run but the one from the 1970's takes four of five pulls to start. I'm not sure what's wrong with it since I never change the oil or spark plugs in them. I just run my lawnmowers until one day they die and I go buy another. My riding lawnmowers usually don't last much more than 15-20 years.