Yamaha 4HP 4 stoke cuts out after 15 mins

[tudorsailor]

Can an expert help?

I have a 10 year old Yamaha outboard 4hp 4 stroke. Over the winter it was "serviced" but then the guy who brought it back laid it on the wrong side so that oil went into the cylinder and it would not start. The service guys took it back cleaned it up and cleaned the carburetor which was apparently "glazed". I threw away last seasons fuel and have new fuel in the external tank.

Now it starts first time when cold. After running for about 15 minutes it dies and cannot be restarted straight away. After a 1/2 hour rest it starts and then dies after 3 minutes.

There is no water coming out the tell tale spurt but there is lots coming out at the base. The leg seems to be quite hot and certainly too hot to hold, but I have never felt it when running to know what normal is. The exhaust is a bit smoky. There is a little bit of hot water escaping from the rubber seal between leg and foot. The breather on the external tank is open(!).

So is this an over heating problem? I am currently in Greece. What do I ask a mechanic to do? ( I don't have the skill/experience to dismantle myself unless it a simple task. I can fix hands but not outboards!)

Thanks in anticipation....

TudorSailor (on my way to Paxos)

 

[RichardS]

I'm not sure how an outboard could be "serviced" and yet returned with no telltale output. I guess that's why serviced is in inverted commas!

It sounds to me like a waterway is blocked and the engine is overheating and a cut-out is operating.

You could try pushing some fine wire up/down the various vents and the telltale (you might be able to remove an end-cap from the tell-tale to give better access. Getting the telltale to operate even a dribble is not the whole answer but it's a start. You could then try removing the prop and standing the OB in a narrow container and filling it to above the level of the water inlets with fresh water and HCl or vinegar or lemon juice or whatever acid you can lay your hands on and make it as strong as possible (not the HCl). If you run the engine in the acid you might well find that the dribbling telltale starts to get a bit stronger until finally it clears.

Whether this will clear all the internal waterways and stop the overheating is a different question but it's probably the least "technical" thing you can do.

Richard

 

[dom]

Agree with Richard, especially re the ""service"" and wld add the following:

First, don't obsess over the telltale; it is just that, as you infer. The very hot shaft is however an indicator that something is in fact wrong. Can I recommend you pch an IR gun on AmaBay (cost v little) as this will give you some definitive readings. Also get a piece of wire and run the engine whilst poking around the telltale. If you get the odd spurt of hot water then the impeller is probably ok, If not, this might too be suspect.

Second, can I ask if you regularly flush the engine? If not -- like 99% of us -- then the waterways could be plugged with a salt/sand/grit mixture that easily clogs the cooling channels and especially the small divert to the telltale. Cleaning these channels is however no big deal and if you can mend hands you can mend this - believe me

As a starting point you can remove the thermostat (really easy) and examine it for salt clogging. If clogged, the other channels will be also. If not, that's great. Also test it in a cup of hot water as if it won't open, then Bingo.

 

[steve66]

Agree with Richard, especially re the ""service"" and wld add the following:

First, don't obsess over the telltale; it is just that, as you infer. The very hot shaft is however an indicator that something is in fact wrong. Can I recommend you pch an IR gun on AmaBay (cost v little) as this will give you some definitive readings. Also get a piece of wire and run the engine whilst poking around the telltale. If you get the odd spurt of hot water then the impeller is probably ok, If not, this might too be suspect.

Second, can I ask if you regularly flush the engine? If not -- like 99% of us -- then the waterways could be plugged with a salt/sand/grit mixture that easily clogs the cooling channels and especially the small divert to the telltale. Cleaning these channels is however no big deal and if you can mend hands you can mend this - believe me

As a starting point you can remove the thermostat (really easy) and examine it for salt clogging. If clogged, the other channels will be also. If not, that's great. Also test it in a cup of hot water as if it won't open, then Bingo.

It could be lots of things. Fuel starvation, bad coil, bad plug , head gasket, overheating ,valve issues etc.
You will need a proper diagnosis to get to the bottom of it

 

[dom]

It could be lots of things. Fuel starvation, bad coil, bad plug , head gasket, overheating ,valve issues etc.
You will need a proper diagnosis to get to the bottom of it

Of course it could, but OP suspects heating and he has to start somewhere. They're not hugely complicated engines after all.

I personally can't see how telling him that he "needs a proper diagnosis" is particularly helpful, but each to his own.

 

[steve66]

Rebuilt many small 4 stroke outboards Dom?

 

[RichardS]

Rebuilt many small 4 stroke outboards Dom?

If I had rebuilt many and I was asked to look at one which has no telltale stream, a leg which is too hot to touch and which starts first time when cold but after running for about 15 minutes it dies and cannot be restarted straight away. After a 1/2 hour rest it starts and then dies after 3 minutes , I would start with water circulation and overheating rather than waste time on fuel starvation, bad coil, bad plug , head gasket ,valve issues which are all non-starters (see what I did there?)

Richard

 

[steve66]

He said water is pumping from lower down the leg . Could be a blocked rell tale?
Could be a coil or plug breakking down when warm, had that a few times lately. Could be a leaking head gasket fouling the plug, again had that issue lately. Could be fuel starvation from a blocked vent or carb issue...
Take your pick. Thats why I said it needs a proper assesment

 

[RichardS]

Could be a coil or plug breakking down when warm, had that a few times lately. Could be a leaking head gasket fouling the plug, again had that issue lately. Could be fuel starvation from a blocked vent or carb issue...
Take your pick. Thats why I said it needs a proper assesment

And just how do any of those account for the leg being too hot to touch?

Richard

 

[steve66]

And just how do any of those account for the leg being too hot to touch?

Richard

Possibly linked possibly not. The motor will need to be assessed in a workshop not over the internet. The original poster asked for ideas not how to repair it

 

[RichardS]

Possibly linked possibly not. The motor will need to be assessed in a workshop not over the internet. The original poster asked for ideas not how to repair it

Obviously I don't know how much experience you have Steve, but this is Practical Boat Owner so suggesting a series of disparate issues and then advising that the OP takes the outboard to a workshop is not usually the "Forum spirit". The OP asked for a "simple" remedy so we have suggested some. Obviously, if they fail to remedy the problem, then a trip to a workshop would be the next step in the OP's case.

Nothing meant against you.

Richard

 

[steve66]

Obviously I don't know how much experience you have Steve, but this is Practical Boat Owner so suggesting a series of disparate issues and then advising that the OP takes the outboard to a workshop is not usually the "Forum spirit". The OP asked for a "simple" remedy so we have suggested some. Obviously, if they fail to remedy the problem, then a trip to a workshop would be the next step in the OP's case.

Nothing meant against you.

Richard

No offence taken. A simple remedy to you may not be simple to someone lacking confidence in repair. I do offer advice to anyone and everyone but in this case i would leave it to an expert.

 

[dom]

No offence taken. A simple remedy to you may not be simple to someone lacking confidence in repair. I do offer advice to anyone and everyone but in this case i would leave it to an expert.

If that is the only advice you have then fair enough. It doesn't however answer the OP's question who -- having already had a bad experience with a so called "expert" -- has specifically asked for a few pointers to at least discuss with another mechanic..

And FWIW, I absolutely stand by my original advice. A dry telltale and a super-hot shaft would most definitely have me thinking cooling. And a cheap IR gun might just save the OP's engine from damage no expert could recover it from. I would also recommend lifting the lid to examine the paintwork for any heat discolouration.

A quick examination of the thermostat should reveal lots about the waterway condition and also rule a potential problem out. A 10 min job and he might be on his way. Or perhaps a spell in a bucket of pickling vinegar and then on his way.

 

[VicS]

And just how do any of those account for the leg being too hot to touch?

Richard

Can an expert help?

[highlight]I have a 10 year old Yamaha outboard 4hp 4 stroke.[/highlight] Over the winter it was "serviced" but then the guy who brought it back laid it on the wrong side so that oil went into the cylinder and it would not start. The service guys took it back cleaned it up and cleaned the carburetor which was apparently "glazed". I threw away last seasons fuel and have new fuel in the external tank.

[highlight]Now it starts first time when cold. After running for about 15 minutes it dies and cannot be restarted straight away. After a 1/2 hour rest it starts and then dies after 3 minutes.[/highlight]

[highlight]There is no water coming out the tell tale spurt but there is lots coming out at the base. The leg seems to be quite hot and certainly too hot to hold, but I have never felt it when running to know what normal is.[/highlight] The exhaust is a bit smoky. [highlight]There is a little bit of hot water escaping from the rubber seal between leg and foot.[/highlight] The breather on the external tank is open(!).

So is this an over heating problem? I am currently in Greece. [highlight] What do I ask a mechanic to do?[/highlight] ( I don't have the skill/experience to dismantle myself unless it a simple task. I can fix hands but not outboards!)

Thanks in anticipation....

TudorSailor (on my way to Paxos)

It seems that there could be multiple issues.

There may be fuel problems ~~~ Have you checked the in line fuel filter? Can you keep it running by repeatedly squeezing the fuel line bulb?

There may be cooling issues. The lack of flow from the telltale suggest that the pump is not pumping ........ but I don't understand the water escaping from the rubber seal ( what rubber seal ?? ) between the exhaust housing and the gear case assembly. That area should be under water unless you are running it in insufficient depth of water or on muffs. If it's on muffs expect water to escape from various places and don't be surprised if you dont get it to pee properly from the telltale. Run it at the correct depth in a barrel to test it.

Of course the exhaust housing will be hot...... it has hot water from the powerhead and hot exhaust gases passing through it. People with delicate hands , like a surgeon, will find it to hot to hold. People with thick skin and hard horny hands (like RichardS) will probably be able to hold it without problems.
If steam is issuing from anywhere or if there are signs of paint discolouration or if a splash of water anywhere on the powerhead sizzles and boils it is overheating.

I appreciate you are not inclined to fix this yourself and, therefore, suggest you tell your chosen mechanics of your concerns and leave it for them to diagnose the causes and sort it out

 

[RichardS]

I appreciate you are not inclined to fix this yourself .......

...... unless we can offer a suggestion which only involves a simple level of dismantling, as in post #2. :encouragement:

Richard

 

[davidpbo]

I had a Yamaha 3.5 2 stroke with no tell tale jet. In my case the temperature of the leg which was only warm led me to believe it was not serious although I did get the top off and clean the water channels. It does sound as though it is an overheating problem, I wonder whether the engine is in fact seizing then freeing up when it has cooled a bit only the seize again when run for a bit.

 

[VicS]

...... unless we can offer a suggestion which only involves a simple level of dismantling, as in post #2. :encouragement:

Richard

Perhaps through his medical contacts he could get some tamsulosin hydrochloride and see if that will get it peeing properly

 

[RichardS]

Perhaps through his medical contacts he could get some tamsulosin hydrochloride and see if that will get it peeing properly

I was on that stuff for about 5 years but I'm not sure that it actually did me much good. A TURP operation two years ago solved all the problems but that presumably isn't going to help the OP or his outboard.

Richard