Mariner outboard motor fault

[ProDave]

We launched our boat today from the trailer at the slipway. An excercise that became a bit hairey as the outboard would not then start. We ended up walking her around the harbour wall on a long rope to get her onto her berth to get us out of trouble.

Firstly that shows it was wise to choose a mooring next to the slip way. The alternative one we considered was a mile away, and we would hve been stuck without the motor had we chosen that one.

Anyway back the the problem. It's a Mariner 4, 2 stroke short shaft outboard that came with the boat and was serviced by the broker immediately before we collected the boat. I had tested it at home as well in an improvised tank and all seemed fine.

But now, it will start and run for a maximum of 30 seconds before dying, and even when running it will die instantly if you try and use any power, even just engaging gear kills it.

The only thing I can think is bad fuel. There was only a tiny bit of fuel in the tank of the engine when we got it (that's what it was previosuly tested with) Before launch, I filled up the tank with the fuel that came in a petrol can with the boat marked "100:1 2 stroke mix" It looked and smelled right, but could this be old stale fuel?

I guess the first think is completely drain the tank and start with fresh fuel. If not I guess it's back to the dealer that serviced it to find out what they have done wrong.

Any suggestions?

 

[VicS]

What age or serial number?

Any doubts about the fuel .. ditch it and refill with fresh, in fact never trust fuel in a can that you have not bought and mixed youself .. it could be almost anything, although i dont think your symptoms are those of stale fuel

Always check the sparks and the plugs before doing anything else. Check clean regap them or replace them if in doubt.

I suspect the carb may need cleaning. Does it help at all if you close or partly close the choke. If it does then carb clean is definitely the next item on the agenda.

Is 100:1 the correct mix? I'd have expected 50:1

I reckon though that if you have been sold a motor with a statement that it had just been serviced and it failed at the first use then its back to the person who serviced it.

 

[bonny]

I had a similar problem years ago with a Mercury 4 2 stroke in a Swift 18 (engine in well). It always ran fine in a tank. The problem turned out to be that the outboard was too low in the water. The leg fills up with water and as soon as you apply any throttle the pressure in the exhaust leg builds up because it can't push the water out quick enough so the engine stalls. Raising it to the recommended insertion depth cured the problem. When we sold the boat (we kept the o/b for a tender) we saw the new owners having the same problem with a Honda 5 4 stroke. We educated them and their problem was also solved.

Of course, this may not be your problem, but it's one that's not obvious. I can't remember the recommended depth but from memory the cavitation plate should be no more than a few inches below the surface.

Otherwise the problem sound like fuel starvation. Is the filter blocked, water in the bottom of the carb (slacken drain screw to drain, any water in there will be obvious as it will bead). Stale petrol does tend to smell rather odd.

 

[fergie_mac66]

We launched our boat today from the trailer at the slipway. An excercise that became a bit hairey as the outboard would not then start. We ended up walking her around the harbour wall on a long rope to get her onto her berth to get us out of trouble.

Firstly that shows it was wise to choose a mooring next to the slip way. The alternative one we considered was a mile away, and we would hve been stuck without the motor had we chosen that one.

Anyway back the the problem. It's a Mariner 4, 2 stroke short shaft outboard that came with the boat and was serviced by the broker immediately before we collected the boat. I had tested it at home as well in an improvised tank and all seemed fine.

But now, it will start and run for a maximum of 30 seconds before dying, and even when running it will die instantly if you try and use any power, even just engaging gear kills it.

The only thing I can think is bad fuel. There was only a tiny bit of fuel in the tank of the engine when we got it (that's what it was previosuly tested with) Before launch, I filled up the tank with the fuel that came in a petrol can with the boat marked "100:1 2 stroke mix" It looked and smelled right, but could this be old stale fuel?

I guess the first think is completely drain the tank and start with fresh fuel. If not I guess it's back to the dealer that serviced it to find out what they have done wrong.

Any suggestions?

you should have oars or paddles as well as outboard and rope !

 

[ProDave]

Yes we have some paddles. I did suggest we paddle across, but my wife didn't think much of that idea, the long rope was more appealing.

The motor is a 2003 model. The plug should be fine as the motor was just serviced but I haven't checked it. Note to ones self, an appropriate size spark plug spanner needs to be part of the boats tool kit.

I am also sure the problem was not too deep in the water.

 

[fergie_mac66]

seriously

get some new fuel quick make sure you have the right mix of oil maybe a tiny bit extra oil if its not been used for long. Get new plug. and have a spare sometimes worth having a second spare plug thats 1 number hotter.Make sure you have a shear pin or two in the clip on the engine plus the tools to change it .

 

[lw395]

In my experience, about 90% of small outboard problems are due to water in the carb.
There is a drain screw in the float bowl, I think on your engine there is a rubber bung under it in the casing, so you can drain the float bowl easily.
If you catch the fuel in a cut-off milk container or jam jar, you may see a small drop or two of water. But it only takes a small drop to fill the main jet.
Take the screw right out and turn the fuel on, you should see fuel run out, if it isn't clean, maybe the tank is rusting?
If it doesn't run out, you have a problem with either a blockage or sticking float valve.
Just let half a cupful run through, it may bring some crud out of the carb.

Personally, i was brought up with dodgy motorbikes and I would strip and clean the carb.
Remove the carb, take the float bowl off and check for dirt. Blow through all the jets.
Work on a sheet of white paper to be sure it goes back together spotless. (we have to relax these standards when doing the job halfway down the harbour!)
But you may wish to leave this to a dealer.

Fuel going stale is an over-stated problem, unless the container is not airtight, but getting some fresh fuel in a spare 5litre can is a good investment anyway. The engine will use a surprising amount of fuel if you push the yacht against the tide with it, and a reserve can is nice to have. So try ruling out that possibility.

Whip the plug out. If it's black and oily, get a new one, NGK are best IMHO. Have a spare on board anyway.

Check the fuel cap breather is actually opening, it has been known for the rubber seal to stick shut.

I used a fairly beaten up Mariner 4 for years, it is a good engine (especially if it's really a yam with the 3 tuning forks logo on the castings). I have a theory that the best reason to believe a two stroke will work is because it worked well last week, so use it often and it should be fine.

Another piece of advice I will share is to join a club and help others with their boats, then when things get awkward someone will return the favour.

 

[fergie_mac66]

Tools

Plug spanner is a given but should go in small waterpoof bag with shearpin tools and spare dead mans key. Or small cable tie to use instead off for emergency if you can find space for the bag securly under outboard top that doesnt catch on anything worth doing .
dont ever forget 2 stroke oil would always use the best !!

 

[yoda]

I would drain the carb and tank to see if there is any evidence of water. Also check the filter that can often be found as part of the fuel valve when removed from the tank. If you are confident take the carb to pieces and clean it out. Check the air vent on the tank is clear. (I assume that it has an integral tank, If not check that the fuel line is clear and not drawing air or the non return valve in the primer bulb sticking.)

Yoda

 

[lw395]

Yes we have some paddles. I did suggest we paddle across, but my wife didn't think much of that idea, the long rope was more appealing.

The motor is a 2003 model. The plug should be fine as the motor was just serviced but I haven't checked it. Note to ones self, an appropriate size spark plug spanner needs to be part of the boats tool kit.

Rope is a good call, paddling is harder than it looks.
Your engine is a bit new compared with my old one, but principles are same.
Spare shear pins and pliers to fit is b... good advice.
I had a very basic tool roll that lived with my dinghy, plug spanner, screwdriver that fitted carb drain, comedy chinese pliers to change shear pin, shear pins and split pins.

 

[fergie_mac66]

2 stroke mixed doesn't last as long as petrol unmixed . best to put old petrol into the car tank even a bit of 2 stroke in car will be ok when mixed into 1/2 tank

 

[bonny]

2 stroke mixed doesn't last as long as petrol unmixed . best to put old petrol into the car tank even a bit of 2 stroke in car will be ok when mixed into 1/2 tank

Wouldn't want to risk damaging the cat.

 

[fergie_mac66]

shearpins

I found that I got a good supply of shear pins from the snapped of pins from monel pop rivets
If they are the right size/dia rivets cut hem to length and the cost you can pick them up for nothing if you see anyone with doing some riveting !.. But then again Im from yorkshire !! however only discover when couldnt buy any of right size for my yam 5

 

[VicS]

Yes we have some paddles. I did suggest we paddle across, but my wife didn't think much of that idea, the long rope was more appealing.

The motor is a 2003 model. The plug should be fine as the motor was just serviced but I haven't checked it. Note to ones self, an appropriate size spark plug spanner needs to be part of the boats tool kit.

I am also sure the problem was not too deep in the water.

2003 model, then I still query the 100:1 mix.

You say the plug should be fine as the motor has just been serviced. If it has just been serviced the whole thing should be fine!

Plug should be BP7HS-10 or BPR7HS-10 (gapped at 1.0 mm) and yes a plug spanner and spare plug should be part of the tool kit.

The diagrams do not seem to show a fuel filter. If that is the case then fitting the filter normally fitted to 5 hp models might be wise if possible.

 

[sailduck]

I also have an old mariner 4. It needs full choke to start, and then the choke needs to be turned right off straight away as soon as it fires up. Could it be as simple as that!??

 

[ProDave]

Okay, the motor's on the bench in a home rigged test tank.

Plug out and it looks fine, the gap was a little wide so closed up, but I don't think that's the problem.

Disconnected fuel line into carb, and fuel flows freely when fuel tap turned on, so not blocked tap / filter / air vent.

I can't see a drain plug in the bottom of the carb bowl. Anyone got a picture where I should be looking, or more detailed info on that.

I probably won't do much more today. Tomorrow I'll drain the fuel and put in a fresh mix. Yes it definitely says 100:1 on the motor. I'll use up the old a bit at a time in the lawnmower, that will run on anything and no cat to worry about. Saves the problem of otherwise disposing of it correctly.

 

[duncan]

2003 model, then I still query the 100:1 mix.

You say the plug should be fine as the motor has just been serviced. If it has just been serviced the whole thing should be fine!

Plug should be BP7HS-10 or BPR7HS-10 (gapped at 1.0 mm) and yes a plug spanner and spare plug should be part of the tool kit.

The diagrams do not seem to show a fuel filter. If that is the case then fitting the filter normally fitted to 5 hp models might be wise if possible.

mine's 2002 and is 100:1

mind you it's a special example of this model as it runs fine on old (very) fuel left in the tank.

I would start with the obvious potential restrictions -
1. air vent - is is open sufficiently and 'clear'
2. fuel tap - same as above.

I don't think there is a fuel filter either, I added a small cartridge one when installing a fitting for remote tank. Possible there is a simple gauze or similar above the fuel tap?

Plug and carb have been mentioned

Edit - the above was of course being typed as the above post was made!

 

[fergie_mac66]

pump

think mariner is similar to yam' I had prob on my yam (7/8 years ago )with the fuel pump its a little diaphragm thing square with 4 screws the air hole in between the back of the diaphragm into the inlet port got some muck in it works by the the inlet suction pulls the diaphragm and then on the exhaust stroke a spring pushes it back forcing the the petrol into the carb (theres a non return valve in the fuel line going into the pump )

 

[VicS]

think mariner is similar to yam' I had prob on my yam (7/8 years ago )with the fuel pump its a little diaphragm thing square with 4 screws the air hole in between the back of the diaphragm into the inlet port got some muck in it works by the the inlet suction pulls the diaphragm and then on the exhaust stroke a spring pushes it back forcing the the petrol into the carb (theres a non return valve in the fuel line going into the pump )

Isn't the engine in question just gravity fed ? I did not see any fuel pump on the parts diagrams!

 

[fergie_mac66]

Okay, the motor's on the bench in a home rigged test tank.

Plug out and it looks fine, the gap was a little wide so closed up, but I don't think that's the problem.

Disconnected fuel line into carb, and fuel flows freely when fuel tap turned on, so not blocked tap / filter / air vent.

I can't see a drain plug in the bottom of the carb bowl. Anyone got a picture where I should be looking, or more detailed info on that.

I probably won't do much more today. Tomorrow I'll drain the fuel and put in a fresh mix. Yes it definitely says 100:1 on the motor. I'll use up the old a bit at a time in the lawnmower, that will run on anything and no cat to worry about. Saves the problem of otherwise disposing of it correctly.

the drain is a screw right on the bottom of the carb usually has a small compressed coil spring on it. its a flat head screw probably slotted not pozi /philips about 5 mm dia it doesnt have to come all the way out