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Yamaha F250 intermittent Cranking problem

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boomerfishing

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I have twin Yamaha 250 HP 4 strokes on my 30” boat. The engines were manufactured in 2006, but the boat wasn’t commissioned until 2011. So there are only 2 seasons on the motors. They are models F250 and LF250. I have separate brand new #27 batteries installed. The boat has been only used twice with this setup. First thing in the morning, both engine jump to life when the key is touched. During the day, usually after several hours, one of the engines hesitates to crank over. When the key is backed off and re-applied the engine jumps to life. It usually starts on the second try, but rarely I have had to hit the key a third time. When I return to the dock and let the boat sit (engines off) for a while, the engine jumps right to start. One mechanic said it could be a vapor lock. I know the words, but don’t really know how this really means. Any ideas would be appreciated.
 
If it is slow to turn over it is possibly an electrical issue. Could be a loose battery terminal connection or similar inside the engine. Could also be to do with the starter solenoid not making good contact (not sure if it is adjustable or not). If you know how to use a volt meter you could try checking the voltage at the starter motor +ve terminal on the engine when trying to start it and see if it is unusually low when it won't turn over.
 
Thanks for the reply. I think that I have consensus that you are correct. We are targeting a ground post that Yamaha uses. We tightened that and are hoping that we have solved the problem. We won't know until we get out again. Thanks again. Ed
 
boomerfishing said:
Thanks for the reply. I think that I have consensus that you are correct. We are targeting a ground post that Yamaha uses. We tightened that and are hoping that we have solved the problem. We won't know until we get out again. Thanks again. Ed
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I would check all battery connections. Positive and Negative on the battery, the battery switches and the engine.
 
I agree that it is more than likely a connection issue. I am not buying vapor lock. Easy way to check is to feel of the primer bulb after running for a while. Is it hard? If so your issue is more than likely else where!
 
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