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I have a 1993 Yamaha outboard 2 stroke. Which is only

Hi I have a...

Hi I have a 1993 Yamaha outboard 2 stroke. Which is only running on two of the three cylinders

Mechanic's Assistant: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

I just replaced head gasket. Replaced fuel pump.Cleaned the carburettor s.could it still be a fuel problem?

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1/16/2018
Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 4,916
Experience: US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Hello, my name is***** will assist you.

Have you also done a compression test on the engine?

Do you also have the full model number of it?

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Customer reply replied 7 months ago
Hi Charles. The model is 40HETO 6H4L

Thanks.

Have you done a compression test on it. That really is where we should start.

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Customer reply replied 7 months ago
MODEL 40 HETO 6H4L 532698
Customer reply replied 7 months ago
COMPRESSION TEST was 126 125 130. Seems to be not running on all cylinders. will only start with full choke and keep running at high revs ,has a cough backfire also
Customer reply replied 7 months ago
I have had someone look at it and he wanted to take carby:s apart again and clean. i,m hesitant about this as I have already done this. Am starting to weigh up the costs of repair .that is why i'm seeking a second opinion.

Thanks.

Will the engine run better and on all cylinders with either the choke on or your hand held in front of each carb?

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Customer reply replied 7 months ago
It seems to run better with the choke on. I have not tried holding my hand over each carb though.

Ok, if it will run better with the choke on, then it is a fuel issue. The idle jets in these carbs are very small and any small piece of debris can clog them. This is why it will run better with the choke, you are reducing the amount of air in the carb and drawing out more fuel. Cleaning and adjusting the carbs should take care f the problem.

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Customer reply replied 7 months ago
OK I will pull the carbs off again and clean. Do I need to sync the carbs after I re assemble??

Sync them, no. You will need to fine tune the mixture needles on them once the engine is running again.

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Customer reply replied 7 months ago
Thanks Charles, can I contact you in a couple of days if I need more advice ?

Sure thing. if it is on this topic, you can just reply back to this thread. If it is on a different part of the engine, I will need for you to start a new question.

Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 4,916
Experience: US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
Verified
Charles and 87 other Boat Specialists are ready to help you
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Customer reply replied 7 months ago
Thanks Charles.

Your very welcome.

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