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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15626
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a 3.0 litre in a Bayliner. it runs fine when it is

Customer Question

I have a 3.0 litre in a Bayliner. it runs fine when it is cold and up to temp. still O.K. After about half hour of boating the motor runs really poor and will stall as soon as you put it in gear.
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hello my name is ***** ***** am I speaking with?

The very first thing that would need to be known is if the engine has spark or not when it stalls. Have you checked for spark output with a timing light when it stalls? If yes, does it have it or is there no spark?

Customer: replied 1 year ago.
The engine will still run but very rough and no power.
Expert:  Jason replied 1 year ago.

The engine might have weak spark. Do you have a hand held voltmeter to measure the voltage at the coil with the engine running?

Customer: replied 1 year ago.
The voltage to the coil is 12 volts
Expert:  Jason replied 1 year ago.

Is that 12 volts when the engine is running fine or 12 volts when the engine is running poorly?

Customer: replied 1 year ago.
When it is running fine. What would make the voltage drop and then recover after the engine is shut down for a couple of hours?
Expert:  Jason replied 1 year ago.

It is points ignition so there is a resistor wire. When running it should actually be closer to 10-11. Are you guessing when you say 12 volts, or did you actually measure it when the engine is running?

Customer: replied 1 year ago.
My mechanic checked it but it was running O.K. at the time.
Expert:  Jason replied 1 year ago.

Are you working on this engine yourself or are you working with a mechanic that can not figure this out, and relaying information to you?

Customer: replied 1 year ago.
I had a mechanic look at it and it is still the same.
Expert:  Jason replied 1 year ago.

Understood. This should not be to hard for the mechanic to figure out, but he does have to duplicate the problem first. When the engine runs fine there is nothing to test for because the engine is running properly. That being said the engine needs 3 things to run. Compression, spark and fuel. Compression never changes, so the engine Is loosing either spark or fuel. The easiest thing to do is duplicate the problem first, and then after that use a tool called an adjustable gap spark tester, this measures the actual spark intensity, and it will tell him if the spark is strong, or weak. If it is weak then he goes back to measuring voltage again. If the resistor wire is starting to burn up that can cause low voltage to the coil when hot. But if spark looks good, then you are looking at a fuel problem. The next step would be running the boat off of another fuel source like a portable tank. If it runs better immediately, there is some kind of blockage or vacuum buildup in the boats fuel tank. If there is no change, then that narrows the problem down to either the fuel pump or the carb. From there fuel pressure can be tested, it would need to be between 3 and 7 psi. If it is low, the fuel pump is the problem. If it is fine, the problem is inside of the carb, and probably is a little dirty and has a sticking float. Does that make sense?

Customer: replied 1 year ago.
Thanks for your help, I will try that.
Expert:  Jason replied 1 year ago.

You are very welcome and I was glad I could help.

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you

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