Outboard Issues - Won't Idle

[Rob Birnie]

I have a 2 stroke Yamaha 30hp CV longshaft that has some issues at the moment.

It will start okay first go but will only run on high revs and won't idle good. It runs on high revs for a bit but will eventually shut off. Once it shuts off it won't start again. 

Can I get any recommendations on any issues it could be? I have changed the spark plugs and about to clean out the carby. Any other suggestions would be greatly appreciated 

[ellicat]

Apart from the carby, it could be the ignition leads.

Could also be fuel related -  split hose; breather valve not open on the tank; split primer bulb; water in fuel (assuming you don't have a filter).

That's my level of diagnostics, sorry. Hopefully one of the more experienced members will have some other options for you to look at.

[GregOug]

The Choke isn’t stuck on, is it?

[Rob Birnie]

20 minutes ago, ellicat said:

Apart from the carby, it could be the ignition leads.

Could also be fuel related -  split hose; breather valve not open on the tank; split primer bulb; water in fuel (assuming you don't have a filter).

That's my level of diagnostics, sorry. Hopefully one of the more experienced members will have some other options for you to look at.

I was going to check the ignition after carby clean out and replace the black ignition box. Seems to be getting fuel okay from the tank so thinking if it is fuel related its around the carby. Thank you for your help! 

[Drop Bear]

How old is the fuel? 

[Rob Birnie]

Just an update. Ended up cleaning the carby and replacing with a carby repair kit. There was a problem with the float which wasn't cutting fuel off and causing the carby to overflow. Fixed this issue and it seemed to be better but the outboard still won't idle great and will shut off. Does this sounds like a CDI problem or something else fuel/ cafby related? 

[GregOug]

14 minutes ago, Rob Birnie said:

Just an update. Ended up cleaning the carby and replacing with a carby repair kit. There was a problem with the float which wasn't cutting fuel off and causing the carby to overflow. Fixed this issue and it seemed to be better but the outboard still won't idle great and will shut off. Does this sounds like a CDI problem or something else fuel/ cafby related? 

As @Drop Bear said, how old is the fuel? And I mentioned checking the choke is not on. 

[Rob Birnie]

1 minute ago, GregOug said:

As @Drop Bear said, how old is the fuel? And I mentioned checking the choke is not on. 

Fuel is brand new, also checked the choke and that seems to be fine as well

[Guest]

1 hour ago, Rob Birnie said:

Fuel is brand new, also checked the choke and that seems to be fine as well

Could be the power pack or the leads as ellicat said before but before you go spending the big bucks eliminate the small stuff. Check your primer hasn't been pin pricked I used to love doing that to my brothers boat when we were kids, breather on the fuel tank, the diaphragm on the side if it's leaking it's sucking air also check your fuel hose for splits I think sounds like something isn't sealing properly it might be something as simple as these things hard to say without seeing it.

[GregOug]

5 hours ago, Sneaky1 said:

Could be the power pack or the leads as ellicat said before but before you go spending the big bucks eliminate the small stuff. Check your primer hasn't been pin pricked I used to love doing that to my brothers boat when we were kids, breather on the fuel tank, the diaphragm on the side if it's leaking it's sucking air also check your fuel hose for splits I think sounds like something isn't sealing properly it might be something as simple as these things hard to say without seeing it.

Yeah. Certainly sounds fuel related to me. It can only be two things. Fuel or spark. And usually you either have spark or you don’t. So starting, running for a while then cutting out means it’s got something to do with fuel, in my opinion.

[Guest]

26 minutes ago, GregOug said:

Yeah. Certainly sounds fuel related to me. It can only be two things. Fuel or spark. And usually you either have spark or you don’t. So starting, running for a while then cutting out means it’s got something to do with fuel, in my opinion.

Yep I agree definitely sounds like a fuel issue , if you do want to check your power pack make up one of these spark testers but I would be checking the fuel system first

[Kenne]

I had similar problems on my 40 hp Merc.  Hadn't had it for long and the previous owner never used it for a long time.

Found the fuel lines and bulb perished on the inside and blocking the fuel system. Replaced the lines ,bulb and filter.

Ran much better but still had probs. Run fine at home in the driveway but not on the water.

Stripped down the carbies and soaked them in carby clean. Amazing what came out of what looked like clean carbies.

Hasn't missed a beat since. 

[Putto]

On 23/11/2020 at 3:10 PM, Rob Birnie said:

Fuel is brand new, also checked the choke and that seems to be fine as well

Mate there is a small casting that directs the exhaust gas that breaks off and restricts the exhaust, Its a common fault with these motors fish the small piece out and you will all good to go

[Putto]

On 28/10/2020 at 12:36 PM, Rob Birnie said:

I have a 2 stroke Yamaha 30hp CV longshaft that has some issues at the moment.

It will start okay first go but will only run on high revs and won't idle good. It runs on high revs for a bit but will eventually shut off. Once it shuts off it won't start again. 

Can I get any recommendations on any issues it could be? I have changed the spark plugs and about to clean out the carby. Any other suggestions would be greatly appreciated 

Mate there is a small casting that directs the exhaust gas that breaks off and restricts the exhaust, Its a common fault with these motors . fish the small piece out and you will all good to go

[Drop Bear]

On 24/11/2020 at 3:13 PM, Putto said:

Mate there is a small casting that directs the exhaust gas that breaks off and restricts the exhaust, Its a common fault with these motors fish the small piece out and you will all good to go

Pro tip Putto,

Welcome to the forum.