Outboard engine advice
Discussion
I’ve got a little 3hp Yamaha Malta on our RIB, just a weekend knockabout thing so nowt serious! Took it out last weekend with my lad and he was having a steer on an empty part of the river when the engine cut out and wouldn’t restart (b
d thing to row back, especially with a 7 year old constantly in the way 
).
I’m going to have a tinker with it at some point (when there’s10 minutes spare!), but just looking at whether there’s anyone might have an idea on first things to look at to save a complete strip down?
- going at probably 3/4 throttle, sounded like fuel starvation, started to cut out even with a little throttling on and off.
- fuel/oil mix looks to be leaking out of a bolt at the bottom of the prop shaft, by the water intake. Lost perhaps an 16th of a tank full through it in ~20 mins once we were back on shore and the engine was upright.
- a little fuel mix was in the bottom of the housing too.
- had it restarted a few days later on a stand, sounded like air getting into the barrel - sort of hollow popping as it ran.
At the moment, I’m thinking perhaps fuel blockage somewhere would explain the splutter and die side of it, but not sure that would allow fuel in to the prop?! Didn’t smell like gearbox oil, definite fuel smell to it.
As above, I’ll have a play myself but if anyone was experienced with these things, would help to know if I was wasting my time before I start!
d thing to row back, especially with a 7 year old constantly in the way ). I’m going to have a tinker with it at some point (when there’s10 minutes spare!), but just looking at whether there’s anyone might have an idea on first things to look at to save a complete strip down?
- going at probably 3/4 throttle, sounded like fuel starvation, started to cut out even with a little throttling on and off.
- fuel/oil mix looks to be leaking out of a bolt at the bottom of the prop shaft, by the water intake. Lost perhaps an 16th of a tank full through it in ~20 mins once we were back on shore and the engine was upright.
- a little fuel mix was in the bottom of the housing too.
- had it restarted a few days later on a stand, sounded like air getting into the barrel - sort of hollow popping as it ran.
At the moment, I’m thinking perhaps fuel blockage somewhere would explain the splutter and die side of it, but not sure that would allow fuel in to the prop?! Didn’t smell like gearbox oil, definite fuel smell to it.
As above, I’ll have a play myself but if anyone was experienced with these things, would help to know if I was wasting my time before I start!
A 2-stroke will pass some oil through the system in normal running - as you will know from the black oily ring round the bucket/bin you use for flushing!
This is entirely normal.
Unburnt petrol/oil mix leaking out isn't - although if you tilt the engine up you might get a little out of the carb intake but it shouldn't be running out.
Fuel tank vent fully open & no blockages?
Check your fuel lines for damage, holes, blockage.
Ditto for any inline fuel filters.
I suggest you strip & clean the carburettor as over time they can get gunged up with fuel & oil deposits.
This can cause a lot of running problems if it blocks the jets & I've seen quite a few recommendations for having them ultra-sonic cleaned.
Resist any temptation to poke things into the jets. Blow them through with an aerosol of carburettor cleaner.
Check all internals - diaphragms, float etc - for damage.
Could also cause the float needle valve to be held off its seat which will allow fuel/oil mix to drain until either the tank is empty or if you've turned a fuel lever off the lines have emptied.
You might find this link of help. Click on the magnifying glass OEM parts symbol & then enter your engine details. You'll find exploded diagrams of the various engine parts.
https://www.crowleymarine.com/
This is entirely normal.
Unburnt petrol/oil mix leaking out isn't - although if you tilt the engine up you might get a little out of the carb intake but it shouldn't be running out.
Fuel tank vent fully open & no blockages?
Check your fuel lines for damage, holes, blockage.
Ditto for any inline fuel filters.
I suggest you strip & clean the carburettor as over time they can get gunged up with fuel & oil deposits.
This can cause a lot of running problems if it blocks the jets & I've seen quite a few recommendations for having them ultra-sonic cleaned.
Resist any temptation to poke things into the jets. Blow them through with an aerosol of carburettor cleaner.
Check all internals - diaphragms, float etc - for damage.
Could also cause the float needle valve to be held off its seat which will allow fuel/oil mix to drain until either the tank is empty or if you've turned a fuel lever off the lines have emptied.
You might find this link of help. Click on the magnifying glass OEM parts symbol & then enter your engine details. You'll find exploded diagrams of the various engine parts.
https://www.crowleymarine.com/
Edited by paintman on Saturday 12th September 12:06
paintman said:
A 2-stroke will pass some oil through the system in normal running - as you will know from the black oily ring round the bucket/bin you use for flushing!
This is entirely normal.
Unburnt petrol/oil mix leaking out isn't - although if you tilt the engine up you might get a little out of the carb intake but it shouldn't be running out.
Fuel tank vent fully open & no blockages?
Check your fuel lines for damage, holes, blockage.
Ditto for any inline fuel filters.
I suggest you strip & clean the carburettor as over time they can get gunged up with fuel & oil deposits.
This can cause a lot of running problems if it blocks the jets & I've seen quite a few recommendations for having them ultra-sonic cleaned.
Resist any temptation to poke things into the jets. Blow them through with an aerosol of carburettor cleaner.
Check all internals - diaphragms, float etc - for damage.
Could also cause the float needle valve to be held off its seat which will allow fuel/oil mix to drain until either the tank is empty or if you've turned a fuel lever off the lines have emptied.
You might find this link of help. Click on the magnifying glass OEM parts symbol & then enter your engine details. You'll find exploded diagrams of the various engine parts.
https://www.crowleymarine.com/
Top man, thank you very much!This is entirely normal.
Unburnt petrol/oil mix leaking out isn't - although if you tilt the engine up you might get a little out of the carb intake but it shouldn't be running out.
Fuel tank vent fully open & no blockages?
Check your fuel lines for damage, holes, blockage.
Ditto for any inline fuel filters.
I suggest you strip & clean the carburettor as over time they can get gunged up with fuel & oil deposits.
This can cause a lot of running problems if it blocks the jets & I've seen quite a few recommendations for having them ultra-sonic cleaned.
Resist any temptation to poke things into the jets. Blow them through with an aerosol of carburettor cleaner.
Check all internals - diaphragms, float etc - for damage.
Could also cause the float needle valve to be held off its seat which will allow fuel/oil mix to drain until either the tank is empty or if you've turned a fuel lever off the lines have emptied.
You might find this link of help. Click on the magnifying glass OEM parts symbol & then enter your engine details. You'll find exploded diagrams of the various engine parts.
https://www.crowleymarine.com/
Edited by paintman on Saturday 12th September 12:06
Interestingly, I don’t get the oily ring (ooh err) in the wheelie bin with this one. Have with every other one I’ve had though.
Huntsman said:
I have my own golden rule with outboards, especially little ones that at 10 years old i get a new one and sell off the old one.
Having said that in the stable I have a 3.5hp Mercury 4 stroke that was my dads. Its barely been used. Not sure how old it is. I'll check. I could sell it.
Fancy swapping it for a stunning Yamaha Malta 3hp? Works a treat, absolutely no issues whatsoever, guv. Having said that in the stable I have a 3.5hp Mercury 4 stroke that was my dads. Its barely been used. Not sure how old it is. I'll check. I could sell it.
Being a two stroke outboard, it could be the seals in the crankcase, which form an airtight seal around the crankshaft, have failed. They can dry out with age and once they leak they will let additional air in when the piston is going up the cylinder, resulting in a lean mix, hence the cutting out. It is possible they would also allow unburnt fuel/oil mix to leak out of the crankcase and down the leg.
Yamaha Malta Crankcase Oil Seals
Yamaha Malta Crankcase Oil Seals
GliderRider said:
Being a two stroke outboard, it could be the seals in the crankcase, which form an airtight seal around the crankshaft, have failed. They can dry out with age and once they leak they will let additional air in when the piston is going up the cylinder, resulting in a lean mix, hence the cutting out. It is possible they would also allow unburnt fuel/oil mix to leak out of the crankcase and down the leg.
Yamaha Malta Crankcase Oil Seals
That’s a good shout, Will have a look at that, thanks Yamaha Malta Crankcase Oil Seals
We have an old yamaha 2hp and they will basically keep going forever, cant replace them with anything nearly as light, as 2strokes are now banned.
I would certainly check the plug if its been run a slow speed (more like half or less) because that will oil up the plug a treat!
Does it have an inline fuel filter, if not I would fit one, cheap insurance against shte in the carb.
Daniel
I would certainly check the plug if its been run a slow speed (more like half or less) because that will oil up the plug a treat!
Does it have an inline fuel filter, if not I would fit one, cheap insurance against shte in the carb.
Daniel
Strip and clean the carb, make sure you remove and clean the jets. As above, it could be the float valve sticking if you’re getting fuel leaking through, you can normally tell by the feel of the priming bulb if the valve has sealed however you may not have a bulb on a small engine?...
Check the tank for contamination, if it’s suddenly my cut out it sounds like it may have sucked some dirt through blocking a jet?
Check the tank for contamination, if it’s suddenly my cut out it sounds like it may have sucked some dirt through blocking a jet?
But of an update on this and a follow up question if I may...
Found that the issue with the engine was down to, amongst a few other bits, the water pump housing having melted!! Literally, melted! The waterways were about 1/8th the size they should be due to scum and salt and the impeller was in with no woodruff key on the prop so wasn’t actually spinning either! Brilliantly maintained by the previous owner, brilliantly!
So, I’ve done a full strip and rebuild on it. Re-threaded every bolt , replaced every gasket etc etc. Once the final part is solved, she should run like a charm
However, now it won’t come out of gear?! The gear shaft is connected to the rod in the gearbox properly and shifts up and down perfectly well from the switch on the cowling. The gear rod shifts well and i can see something at the back of the gearbox sliding up and down at the same time (gear selector, I guess), but it just seems to want to stay in forward. I haven’t put the propeller back on so I’m wondering if, by not having that bolted on, the selector in the ‘box is just pushing the whole setup forward rather than just disengaging forward?
Any thoughts?
Found that the issue with the engine was down to, amongst a few other bits, the water pump housing having melted!! Literally, melted! The waterways were about 1/8th the size they should be due to scum and salt and the impeller was in with no woodruff key on the prop so wasn’t actually spinning either! Brilliantly maintained by the previous owner, brilliantly!
So, I’ve done a full strip and rebuild on it. Re-threaded every bolt , replaced every gasket etc etc. Once the final part is solved, she should run like a charm
However, now it won’t come out of gear?! The gear shaft is connected to the rod in the gearbox properly and shifts up and down perfectly well from the switch on the cowling. The gear rod shifts well and i can see something at the back of the gearbox sliding up and down at the same time (gear selector, I guess), but it just seems to want to stay in forward. I haven’t put the propeller back on so I’m wondering if, by not having that bolted on, the selector in the ‘box is just pushing the whole setup forward rather than just disengaging forward?
Any thoughts?
dhutch said:
We have an old yamaha 2hp and they will basically keep going forever, cant replace them with anything nearly as light, as 2strokes are now banned.
I would certainly check the plug if its been run a slow speed (more like half or less) because that will oil up the plug a treat!
Does it have an inline fuel filter, if not I would fit one, cheap insurance against shte in the carb.
Daniel
I recall my grandfather dropping one off a transom into the sea. He fished it out with a rope and grappling hook at low tide, gave it a warm freshwater bath (in the bath!), left it to dry in the summer room, replaced the fuel and off it went...I would certainly check the plug if its been run a slow speed (more like half or less) because that will oil up the plug a treat!
Does it have an inline fuel filter, if not I would fit one, cheap insurance against shte in the carb.
Daniel
I've had a few outboards in the past - probably c.8 smaller 2 strokes amongst lots of others. I find that many of them have attracted dirt into the carb, and have wedged the float down, flooding everything. If I get a sudden stoppage I shake the living daylights out of it on the transom and it generally gets things going. On the one occasion it hasn't, the spark plug has been at fault. IME carbs are the biggest problem with small outboards - overheating rarely is, as even tiny amounts of water being pumped round keep them going well enough to live another day.
Huntsman said:
Sorry. No idea. But I do still have the very nice Mercury 3.5 if you want it.
Cheers anyway bud Does the Mercury run? How much would you be after for it? Once this is finished I’d love another little project for the winter nights
. Would have to convince the finance director it’s worth it though!Gassing Station | Boats, Planes & Trains | Top of Page | What's New | My Stuff