Mercury 3.3 outboard failure - what's wrong?

[sjchilde]

Mercury 3.3 outboard failure - what\'s wrong?

Can anyone suggest what is wrong with this engine?

It was new in 2001, I have previously used it occasionally for a yacht tender, but it hasn't done many hours. This weekend we were using it to push a small yacht (22ft) and it was fine until..

We had been running for about 1 1/2 hours, not flat out, and stopped for a while. Then after restarting it slowed and stopped. Each time I started it, it ran for a while, up to a few minutes, then slowed down and stopped. Once I was quick enough to turn up the throttle as it slowed, this increased the speed briefly then it stopped. This made me think it is not fuel starved. There was nothing on the prop, nothing visibly blocking the water inlet. Was it overheating?if so, is it likely to be seriously damaged by this? Also how do you get to the thermostat and the impeller?

Many thanks for your ideas

Steve

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Just a thought. If you haven't run if for that long in a while, but have had fuel in it, there may be condensation in the tank and you've picked up water from the bottom of the tank. (assuming a built-in tank).
Take the float chamber off without inverting it at any point and see what's in the bottom.
It's something easy to check before you go any further.

 

[VicS]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Fuel tank vent not opened properly or blocked?

Do you have a remote tank if so does pumping the primer bulb keep it going? If so suspect fuel pump.

If its an integal tank is the tap opening properly or is something blocking the tank outlet.

In either case check fuel filter.

Can't help with the pump or thermostst if it has one.

If all else fails go to the Mercury board on The iBoats forums

If you do be sure to quote full model details ie make, hp, year and model number.

 

[Rick]

Re: Mercury 3.3 outboard failure - what\'s wrong?

I've got a 2003 version - waterpump is on leg - remove g'box to access pump body and impellor. The impellor should be changed annually apparently. I don't know if the engine has a thermostat, but was there water coming out the tell-tale when it was running? If it was overheating, then likely to have done considerable damage. I'd remove/replace impellor and if ok, drain and flush fuel tank, anf try again. BTW mine does not like to run on fuel that has been in the tank for much more than a month - I throw away more than I burn.

 

[john_morris_uk]

Re: Mercury 3.3 outboard failure - what\'s wrong?

[ QUOTE ]
BTW mine does not like to run on fuel that has been in the tank for much more than a month - I throw away more than I burn.

[/ QUOTE ]We have the same engine and it gets the same old fuel from one year to the next. Even in the spring I give it a bit of a clean, check for loose bits and fire it up on last years petrol.

 

[gandy]

Re: Mercury 3.3 outboard failure - what\'s wrong?

For a quick check on the fuel, there's a drain screw on the carb float bowl which should be accessible without dismantling. See what comes out.

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Good point. I don't know that particular engine.

 

[yoda]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Ensure water exiting from tell tale. Ensure no water in fuel tank and clean float chamber of the carb. Ensure tank vent is opening correctly. Clean fuel filter which can be found by removing the fuel tap from the tank.

Yoda

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Yoda,
Have you read any of the rest of the thread?

 

[sjchilde]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Thanks folk,up to now I have found the fuel is flowing nicely out of the drain in the carb float chamber, and there is no water in it. So I am tending towards thinking it overheated. Just at pres I haven't removed the gearbox, cos one of the screws was fixed in with saltwater corrosion and it will take a little time to shift it.

Meanwhile can anyone tell me what damage I may have done if it did overheat? It will still turn and it was running ok just before it stopped each time....

Many thanks

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

I don't know how old you are, but if you think back to Lambrettas, they would seize up several times on a run to the coast. Downhill with the trhottle closed was always risky.
They still seemed to keep going though. I never got around to running bearings 'till I progressed to cars.

 

[Major Catastrophe]

Re: Mercury 3.3 outboard failure - what\'s wrong?

I bought a second hand Mercury 3.3 in June. On first run out I thought what was the tell tail was working, but it wasn't and engine kept stopping as it overheated. Luckily, before any damage was done, the seller discovered that the impellor locating rod had popped out, so it wasn't turning impellor. This was fixed.

I then used 2 stroke B&Q oil and it kept stopping and then I had a blonde moment when mixing genuine marine 2 stroke and for some reason just poured the measured oil into the fuel tank, instead of into 5 litre petrol can. After buying another petrol can to drain the mess into I eventually managed to fill up with a good mix.

I set off, but within two minutes was rowing the tender again. Headed back to the seller who kindly opened the breather cap for me.

So, three reasons for a 3.3 Mercury engine to keep stopping.

Usual Catastrophe for me.

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Tell me about this trailer.

 

[Major Catastrophe]

Re: Mercury 3.3 outboard failure - what\'s wrong?

[ QUOTE ]

Tell me about this trailer.

[/ QUOTE ] That was another catastrophe and totally unrelated to the Mercury catastrophe.

 

[Lakesailor]

Re: Mercury 3.3 outboard failure - what\'s wrong?

I think I heard a rumour.

 

[sjchilde]

Re: Mercury 3.3 outboard failure - what\'s wrong?

I have now stripped the water pump and the top half of the impellor is burnt / melted into the housing. probably not pumping too well. I'll have to try to buy new, can't find the part number yet!

So what is the terrible damage caused by overheating? It seems as though a warped head is unlikely on such a small unit - but is anything else likely to have happened?

Also, why does overheating make an engine stop? It will still turn.

 

[Kawasaki]

Re: Mercury 3.3 outboard failure - what\'s wrong?

When it gets hot everything gets BIGGER ,expands,tighter fit etc.
Piston thinks it is moving up and down a hole wat as shrunk.
Doesn,t like it. Lube do,nt like it either,spark plug says"I not playing in this heat either".
Eventually a mild coronary , motor can,t breathe properly, arteries tighten and she has a slight feint and passes out.

If the coronary is a mild affair, when all cools down "ring ding ding "again but we don,t feel too healthy and a four minute mile is out of the question without Surgery.

The extent of the surgery is uknown untill an exploratory "op" is performed

The piston/rings/"top end" components are the first part of the motor to suffer because that,s the "business and hottest" end where combustion takes place.

If your lucky and not much damage has occurred, ie slight seizure of the piston and rings in the cylinder. A clean up operation could be a fix.

I the piston/rings/cylinder have had a bad coming together ,parts renewal could be the order of the day.

2 ways to find out. 1. stick it all back together with new waterworks/plumbing bits added. Try it in the tub and see how she behaves.
2 Strip the top end and check the bits in there.

You mention that the motor still turns so there is hope. /forums/images/graemlins/smile.gif

 

[VicS]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Damage to the cylinder walls, piston and rings are the most likely results. Replace the pump impeller and see if it works Ok. If it does then don't try and fix what is not broken! Perhaps be gentle with it for a while.

Why has the impeller melted. Has it been run out of the water. It only takes a few moments to wreck a pump impeller if it is dry.

 

[gandy]

Re: Mercury 3.3 outboard failure - what\'s wrong?

This web site gives exploded diagrams and part numbers.

http://www.ribsmarineparts.co.uk/epc/Default.aspx

It's a bit of a pain to navigate, but it helped me to check the bits my dealer had ordered for me. (She'd got them wrong, as well, so without this site I'd have received a throttle needle instead of a float needle)

 

[sjchilde]

Re: Mercury 3.3 outboard failure - what\'s wrong?

Thanks! It was on the back of a small yacht, and I admit it came out of the water sometimes on waves, but only for a few seconds each time. I can't imagine an impeller wouldn't cope with that, but maybe it sucked in some gravel or something that caused a bit of wear. And it wasn't brand new.
Steve