Johnson 4hp Seahorse question

[Tinnyhead]

G'day all. I bought 10ft tinny and the aforementioned motor a couple of hours ago. Took it down the river. The motor started fine but after about 3 or 4 minutes it stopped. Started it again. 2 or 3 minutes stopped again. Couldn't pull the starter so assumed the motor has overheated. Took it ashore and let it cool down. It started first pull ok after I left it for 10 mins. The motor was serviced about 6 months ago and not used since. Its been sitting on a frame in a shed for all that time.

The question:
Is water supposed to be circulating through the motor to cool it? If so I didn't see any being expelled while i was on the water. Is this indicative of a major (read expensive) problem? I've never owned a boat or motor before so any advice is very much appreciated. I know 2/5ths of 7/8ths of bugger all about such motors.

Cheers
Tinnyhead (aka Mike)

 

[GrumpyOldGit]

Yep, it should have water circulating through it, may need the pump looking at, ie. a new impellor ( about £10-15 ) or simply be a bit bunged up in the cooling system. I trust that it is a 2 stroke and you had the right fuel/oil mix? Too lean on the oil side could nip up the big end or main bearings and sieze her up but be very careful not to overoil as it will be a bu66er to start and will doubtless cut out at a nasty moment !
GOG

 

[oldharry]

Yes should be circulating water, and as GOG says, more than liekly the impellor has failed. If it has been run dry to demonstrate it for more than a minute or two the impellor will have melted/disintegrated. Not a a difficult job, and easily DIYable if you know how. If not, get it to an outboard repair shop and they will do the necessary for not too many beer tokens!

The other likely cause of stoppage - not in this case becaus the motor had seized - but more common is the fuel tank vent screw. This is the little knob in the middle of the filler cap. It is scrrewed down for moving the engine to stop fuel spilling, but must be unscrewed when you run it up, otherwise you will get a tank vacuum, which also stops the engine after a few minutes, but doesnt cause it to lock up as yours did.

 

[VicS]

You dont tell us what model.. What is the model number that will identify it.

Without knowing the model number I cannot say for sure but AFAIK the 4 hp models do not have a pee hole .. but check to see if there is one.

If there is no pee hole you should still see some water , perhaps a few drops or a mist being ejected from the exhaust back pressure relief port on the leg.

If no water is coming from there then knackered pump impeller and/or blocked water passages could be your problem

Lakesailor will be along with alot more info shortly

50:1 is the correct fuel mix for any Johnson or Evinrude 2 stroke post 1968.

Stopping after only 3 or 4 minutes may well be due to a fuel flow problem but would not cause it to lock up.

Difficult to diagnose without more detail.

integral tank or remote tank?

If integral check flow from tank to carb.

If remote try pumping the bulb to see if that keeps it going

 

[pete]

Welcome to the forum
This brings back memories of my old 4hp johnson twin cylinder engine on my tender. I replaced the impellor with a new one and tried all the usual tricks flushing with chemical ect over a couple of months but unfortunately nothing worked I spoke to a outboard engineer and he said it was very common with these engines, eventually I bought a secondhand yamaha 4hp 2 stroke and have never looked back.

Sorry to be so negative but I tell myself I do this for pleasure and that old engine was driving me mad.

Ps the one I had sent a mist out of the back of the leg usually impossible to see when on the move but easily seen when run in a tank
Pete

 

[Dave_Seager]

I too have one of these engines in the shed. Mine also would stop when warmed up and could not be restarted. As has been said, it seems to be a common problem. with this model. It is interesting to hear that an engineer confirms this. I was planning to resurrect mine this year and try to sort it out. I do not think that I will bother now.

 

[Lakesailor]

Sounds very much like overheating. The impeller on these motors is quite a substantial thing, but as has been said, if the tips go they won't pump much water. However, if the motor has been stripped in the past some numpty may have used gasket goo on the powerhead/leg joint. This can squeeze into the narrow channel and block it. See picture (Evinrude and Johnson are the same)

this is as the top of the leg. the copper pipe emerging from the leg and turning into the rubber grommet before the blocked hole comes from the water pump at the bottom of the leg. If you are replacing this flange gasket get the rubber grommet as well as it will have hardened and cracked.



The hole looks like this when cleaned.

Getting the copper pipe back into the grommet and the gear lever into the slot at the bottom of the leg is a nightmare. I disconnected the gear lever from the cam at the top. Much easier.



This is where you split the head from the leg (six small bolts)

At the bottom of the leg you need to take the leg casting off the gearbox to reveal the water pump.

The copper water pipe goes into that black grommet on top of the water pump (replace grommet).



This is the water pump chamber removed.

Take great care to note which way the stainless cup that the impeller sits in is oriented and also which way the flat stainless plate fits onto the leg. Once you have cleaned them up it's not obvious.

When running there will be a steamy mist from those little holes on the leg beneath the swivel bracket.

It is a very fiddly job. Small fingers required. If you are sort of person (like my brother-in-law) who suddenly gets annoyed and flings tools around and calls it a stupid f**king ba**ard thing, then maybe you are not suited to doing it.

 

[Twister_Ken]

If you are sort of person (like my brother-in-law) who suddenly gets annoyed and flings tools around and calls it a stupid f**king ba**ard thing, then maybe you are not suited to doing it.

I think I may be related to him.

 

[rotrax]

There is a group of conservationists in and around Studland Bay that know all about seahorses-dont believe a word they say.................

 

[William_H]

Johnson/Evinrude O/Bs

As I think with all outboards certainly Johnson. The biggest problem is stainless steel screws into aluminium castings. The dissimilar metals provide corrosion which makes screw removal difficult.
If you can get the screws loose without snapping them off you are doing well. The actual design is not so difficult to comprehend. Water pumping certainly on my Johnson 6 has always been the biggest single problem. Yes cutting out after a few minutes seized up is typical of overheating. Fortunately it doesn't seem to do much damage to the piston etc.
Have a go yourself starting with the screws for the power head and the screws attaching the water pump /geearbox at the bottom. Use a short spanner and if they are too tight try heat and solvent type oil. Be patient. If you still don't do any good consult a professional. (who may well say "throw it away") However parts are still available if you can get it apart. good luck olewill

 

[Tinnyhead]

Some pics with discussion

G'day all. Thanks hugely for all the info so far.

This is the beast under discussion. (And no the ute doesn't float )

View attachment 16062This is her. The Model number is 4BAL76M

View attachment 16061 Does the discolouration on the steel plate indicate overheating?

View attachment 16064 There doesn't seem to be a "vent" in the fuel cap so I just loosen the cap a couple of turns.

View attachment 16065When its running the fuel filter is always full. So fuel is getting through

View attachment 16066 Is the crack in the blue thing a problem?

View attachment 16067There is a steady misty spray of water coming from the exhaust so water is getting around the system.

I use the recommended fuel mixture of 50:1

I took the gear box off and checked the impeller. It looks new. Nothing worn perished or hardened. The drive shaft impeller key is slotted in as it should be. All nice and clean. I'm assuming the little fins on the impeller are supposed to be flexible.

The rubber grommet where the water intake tube fits is a bit daggy looking but still flexible and the tube fits well. I put that part together and took the whole leg off the motor and and checked where the water intake tube goes into the housing. Its is hard and grungy looking but it seems to be otherwise serviceable. I cleaned all the water channels and any through holes I could find with RP7 spray until it was dripping from every orifice. The gaskets were the original paper ones with no evidence of synthetic material such as silicon or gasket goo.

I put everything back together (and to William, I had no problems taking it apart. The screws and bolts seem to be galvanised or zinc plated, not SS) and put it on the river again. It ran for a few minutes and then died.

In desperation I visited the local boat place and spoke to a guy who knew the model well. He said if the compression was poor then fuel wouldn't be pumping efficiently but that if the compression was ok then it would be best to take it in for him to have a look at. That'll cost me money I haven't got at the moment.

I don't know how to do a compression test...do I need a special tool of some kind to check it.

Is the motor worth the trouble even?

This is the first boat and motor I've ever owned so I'm a total ignoramus when it comes to working on them though they seem simple enough if you have a good set of tools.

Thanks for your help.
Cheers
Mike

 

[Tinnyhead]

I think I may be related to him.

me too...just ask the missus. Latest victim...my beautiful $3,000 guitar. Splinters!! had it for 28 years....brain snaps are a bad thing....

 

[Tinnyhead]

Update

Just took the tinny for a run again. Ran at half throtle for about 5 minutes then died again. Can't pull the starter. So definitely a cooling problem.

 

[Lakesailor]

me too...just ask the missus. Latest victim...my beautiful $3,000 guitar. Splinters!! had it for 28 years....brain snaps are a bad thing....

Is the motor worth the trouble even?
Cheers
Mike

Hmm, you've already had the thing apart so you aren't doing too bad.

However (in the UK) one of these in good nick will sell for £150 or so. If you are looking at spending even half that at the repair shop it starts getting a bit marginal.
I've had three Johnson/Evinrudes. I like the bigger ones (I had a 70hp) but am a bit unsure about the smaller twins.
I would suggest flogging it and getting a 3.5 Tohatsu/Mariner/Mercury/Nissan (all the same thing) or a 4/5/or hp Tohatsu/Mariner/Mercury/Nissan or Yamaha or Suzuki.

 

[VicS]

G'day all. Thanks hugely for all the info so far.

This is the beast under discussion.

Sorry I cannot see your pictures. I just get a message saying invalid attachment specified.

I suggest you check the procedure for posting attachments in the FAQs or use a photohosting site such as Photobucket

However it a 1976 model but being Australian it is not listed in the on line parts catalogues.

If the plate you refer to is the big flat plate on the LHS then thats the exhaust manifold cover so may well get hot enough to discolor the paint. Worry if the paint on the cylinder head is discoloured.
You should be able to breifly touch any part except the above plate and the cylinder head around the plugs. If its too hot to touch or if a splash of water sizzles and boils its overheating ! If you can touch it and maintain finger contact briefly its not.

There must be a vent in the fuel tank cap.
But take the cap off and try it.

If its a remote tank will it keep going if you keep gently pumping the bulb?


Dunno what the blue thing is without the picture

The spray of water sounds good esp if it continues and does not simply turn to steam.

The compression can be tested with an ordinary automotive compression tester. Do it warm, take out both plugs and test each cylinder separately. Pull it over half a dozen times on the starter cord. Actual figures are not specified but over 80psi would be OK. The two reading readings should be within 10% of each other.
If it starts without difficulty there wont be anything wrong with the compression to worry about.

Plugs by the way should be Champion J6C gapped at 0.030" ( the nearest NGK equivalent is B6S)

These older 4hp Johnsons and Evinrudes are considered by many to be among the best small otboards bar none.

 

[catlotion]

I was planning to resurrect mine this year and try to sort it out. I do not think that I will bother now.

You don't fancy selling the lower plastic cowling by any chance Dave if yours has had it? Ours fell in the marina when I was trying to tweak the carb...

Toby

 

[Tinnyhead]

Hmm, you've already had the thing apart so you aren't doing too bad.

However (in the UK) one of these in good nick will sell for £150 or so. If you are looking at spending even half that at the repair shop it starts getting a bit marginal.
I've had three Johnson/Evinrudes. I like the bigger ones (I had a 70hp) but am a bit unsure about the smaller twins.
I would suggest flogging it and getting a 3.5 Tohatsu/Mariner/Mercury/Nissan (all the same thing) or a 4/5/or hp Tohatsu/Mariner/Mercury/Nissan or Yamaha or Suzuki.

Don't know why the photos don't show. They're just bog standard jpg's. Thanks for the response Lakesailor. I'm an expert now i've had it apart 4 times and it still starts
I'm looking at the brands you suggest on ePay to get an idea of second hand prices. I know if I took mine into a service agent they'd charge around 100 bucks just to check whether it was worth overhauling. So I'm resigned to replacing it which is disappointing. Maybe sell it for parts. Whats the biggest horsepower to use on a 10 foot aluminium dinghy? I only use it on the river which is at my back door
Cheers
Mike

 

[Tinnyhead]

my comments in red.

QUOTE:Sorry I cannot see your pictures. I just get a message saying invalid attachment specified.

I suggest you check the procedure for posting attachments in the FAQs or use a photohosting site such as Photobucket

However it a 1976 model but being Australian it is not listed in the on line parts catalogues.

If the plate you refer to is the big flat plate on the LHS then thats the exhaust manifold cover so may well get hot enough to discolor the paint. Worry if the paint on the cylinder head is discoloured. Cylinder head not discoloured.
You should be able to breifly touch any part except the above plate and the cylinder head around the plugs. If its too hot to touch or if a splash of water sizzles and boils its overheating ! If you can touch it and maintain finger contact briefly its not. I can

There must be a vent in the fuel tank cap. No vent. Unscrewing the cap about 3 turns is how it works. There's an embossed double ended arrow which has the words "closed" on one end and "vent" on t'other.
But take the cap off and try it.

If its a remote tank will it keep going if you keep gently pumping the bulb?No remote tank, integral.


Dunno what the blue thing is without the picture View attachment 16079Its something electrical!

The spray of water sounds good esp if it continues and does not simply turn to steam.

The compression can be tested with an ordinary automotive compression tester. Do it warm, take out both plugs and test each cylinder separately. Pull it over half a dozen times on the starter cord. Actual figures are not specified but over 80psi would be OK. The two reading readings should be within 10% of each other.
If it starts without difficulty there wont be anything wrong with the compression to worry about.It starts first pull everytime (i wish my lawnmower did)

Plugs by the way should be Champion J6C gapped at 0.030" ( the nearest NGK equivalent is B6S) Yep, Champion J6C.

These older 4hp Johnsons and Evinrudes are considered by many to be among the best small otboards bar none.[/QUOTE]
Thanks for the clues.
Cheers
Mike

 

[William_H]

Water cooling system

If the OP takes the water pump/gearbox off again a simple test for the larger 6HP I have found is to push the running garden hose onto the tube that feeds the power head from the pump. If all is well in the top end water galleries I get a good tell tale flow plus water flowing into the exhaust system. Yes I understand this model does not have a tell tale.
Unfortunately the water mist that OP reports out of the exhaust pressure relief holes may well be steam from only a tiny water flow and overheating engine.
It is very easy to remove the cylinder head which enables you to check the water galleries easily.
good luck olewill