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I have a 2016 Yamaha F70 with 110 hours. It runs smooth and efficiently, but lately (since about 90 hours) it has trouble starting for the second or third run of the day.
It fires up immediately at the ramp, but after I have fished a spot for an hour or two, I’ll try to crank it and it will die after a couple of seconds. It might take one or two more cranks to get it to finally turn over and start. This will happen once or twice each outing. Funny it never happens on the last crank to load the boat back on the trailer.
I had all of the 100hr maintenance done in January and the problem still persists. I’m thinking fuel pressure? Spark plugs? Any insight?
 

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Let me know what you end up finding out. I am having a different issue but somewhat similar. After about 30 minutes of running my F70 bogs down... I prime the ball and good for another 30 minutes or so. I am going to start by changing the primer ball. 700 Hours on 2016 F70.
 

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Because of the fuel efficiency of F series Yamaha, the engine will operate for quite some time before fuel pump cavitation due to a fuel restriction or air leak. After changing a thread on 10 micron Yamaha filter between the tank and engine, I started the engine on hose flush and checked for leaks all ok. Trailered for six hours, launched and was half mile from ramp when engine stopped. Could not pump primer bulb tight, so ended up getting towed in. The threads on the Yamaha filter were defective not allowing the filter gasket to contact the filter manifold. Replaced with new filter and problem solved.
 

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I have a 2016 Yamaha F70 with 110 hours. It runs smooth and efficiently, but lately (since about 90 hours) it has trouble starting for the second or third run of the day.
It fires up immediately at the ramp, but after I have fished a spot for an hour or two, I’ll try to crank it and it will die after a couple of seconds. It might take one or two more cranks to get it to finally turn over and start. This will happen once or twice each outing. Funny it never happens on the last crank to load the boat back on the trailer.
I had all of the 100hr maintenance done in January and the problem still persists. I’m thinking fuel pressure? Spark plugs? Any insight?
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I’m having the same issues 2014 f70 115hrs. Primer bulb not staying hard.
 

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Todd make sure you don’t have a kink in the hose under the deck. My buddy had your hull with an F70 and after a few years it started doing this and we figured it out while fishing one day. When he turned the wheel one way it was kinking the hose but not restricting the fuel until the inner liner of the hoss collapsed from the repeated kinking and the motor was shutting down and primer bulb was getting soft.
We replaced the fuel hose from the fuel filter to the primer bulb and it solved the issue. Make sure you make it a few inches longer than the piece you replace.
 

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Mitzi Tournament 17
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Let me know what you end up finding out. I am having a different issue but somewhat similar. After about 30 minutes of running my F70 bogs down... I prime the ball and good for another 30 minutes or so. I am going to start by changing the primer ball. 700 Hours on 2016 F70.
Any resolution with this? I have a 2011 F70 with ~480 hours that has been doing the same thing after 30-40 minutes. I have replaced the entire fuel line, bulb, water separator & housing, and fuel filter. Cranks and runs fine but after it warms up, starts choking out and not getting fuel to the motor.
 
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