[TXJM]

Since so many people seem to lean on this forum for engine advice, I figured i would ask the group if they have any ideas or have experienced the same issue that I have had intermittently. Probably 10 or 12 times over the last couple of years I have had the engine die when running. It always re starts up immediately and I do not have any other symptoms. It is almost like you turn the engine off. When it has died, I turn the key off and then restart, it starts immediately. I do not know if I have to turn the key off before restarting or not. I did find a fuel issue with the filter between the fuel pump and the engine(it was cracked and dripping. I have also changed the separator out multiple times. I had it happen since then, so that wasn’t it. The only commonality I can find is that it does this when I’m running wide open or near that. I get no error on my multifunction tach and the motor is peeing like crazy. Any ideas??
Chip

 

[Smackdaddy53]

Sounds like a fuel system issue from tank to outboard. WOT uses more fuel so it’s probably starving for fuel then cuts out and when you crank back up you’re at low RPM so it has enough fuel. I’d run it on a remote/portable tank and see if it does anything different. If it does it rules out engine issues and you need to troubleshoot tank vent, fuel filter/water separator and primer bulb.

 

[Capt. Gregg McKee]

This sounds like the same vapor lock issue I had with my two previous Yamaha F70s. It would happen about mid-day when the air and outboard were both warm, a few seconds after jumping up on plane. Usually I'd have to pull the vapor hose at the top of the powerhead to vent it and sit for about ten minutes to let things cool. I could always restart them but not without a struggle sometimes. Took them to a local Yamaha dealer three different times (won't mention the name) and they kept telling me they couldn't duplicate the issue or find any other problems. Finally had a non-Yamaha mechanic suggest a higher temp thermostat which I installed myself and that helped a lot. Didn't eliminate the problem but made restarting a lot easier. I have a handful of friends that have had this same problem, too. Other than that, the F70 was a wonderful engine but the dealer's indifference made me switch brands on my new boat.

 

[paint it black]

Yamaha F70 Vaporlock. Happens usually on warm days. Also happens if you're running full speed, then quickly put it into neutral and shut off the motor. When you restart it and start to run it'll shut off. Ways to avoid it is to let it idle for a bit before shutting it off. Sometimes on really hot south florida days you can't avoid it. We ended up double venting the tank and that helped some. I switched to Etec and absolutely loved it. never had a single issue. Now that Evinrude is no more, I am running Tohatsu 60hp. The weird thing is the Tohatsu did it during break in period. Once broken in, it's been flawless. No issues and loving it.

 

[TXJM]

Sounds like a fuel system issue from tank to outboard. WOT uses more fuel so it’s probably starving for fuel then cuts out and when you crank back up you’re at low RPM so it has enough fuel. I’d run it on a remote/portable tank and see if it does anything different. If it does it rules out engine issues and you need to troubleshoot tank vent, fuel filter/water separator and primer bulb.

I will play with a remote tank to eliminate that part of the fuel system. The boat is older and this is a repower, the original engine was a merc 90. I had no problems with fuel flow with that engine. Maybe something has been restricted in the last couple years.
Thanks

 

[TXJM]

This sounds like the same vapor lock issue I had with my two previous Yamaha F70s. It would happen about mid-day when the air and outboard were both warm, a few seconds after jumping up on plane. Usually I'd have to pull the vapor hose at the top of the powerhead to vent it and sit for about ten minutes to let things cool. I could always restart them but not without a struggle sometimes. Took them to a local Yamaha dealer three different times (won't mention the name) and they kept telling me they couldn't duplicate the issue or find any other problems. Finally had a non-Yamaha mechanic suggest a higher temp thermostat which I installed myself and that helped a lot. Didn't eliminate the problem but made restarting a lot easier. I have a handful of friends that have had this same problem, too. Other than that, the F70 was a wonderful engine but the dealer's indifference made me switch brands on my new boat.

The problem happened recently in cool weather and the boat restarts immediately. It starts by just bumping the starter over. But good to know that these engines have a vapor lock issue. The other thing is that the engine seems to go from running fine to stopped. It doesn’t seem to stumble, miss or lose power. I even suspected the kill switch. I ruled the kill switch out because when I played with pulling the kill switch and then putting it back in, the boat would pick right back up.
Thanks
Chip

 

[coconutgroves]

Also, check out this thread - good related info about fuel issues with Yamahas:

2012 Yamaha F70LA hard start

I have a 2012 Yamaha F70LA The issue is when the boat sits for a few days it is very hard to start. I put boat in the water first thing in morning, and it takes 5-7 turns of the key for a few seconds each time for it to fire up. Each turn of the key is plenty long enough to normally turn it...

www.microskiff.com

 

[TXJM]

Update
I was headed out today. The boat started fine to get the boat off the trailer. When I jumped in to go fish after parking, I got nothing when I turned the key. Any chance that the boat cutting off is related to the switch? Plan on tracing everything in the morning.
Chip

 

[Smackdaddy53]

Sounds like you have an electrical problem and that is why it’s cutting out or you have both a fuel issue and an electrical issue. Hard to troubleshoot on a forum. You might want to have it checked at a shop.

 

[Tweenkie]

Check the wires going into the ignition. If they are corroded or the ignition is corroded inside it then it won't complete the circuit. Think of it like an accidental kill switch getting pulled. Thats my guess since it dies like you are turning it off you said. It happened to me once and my buddy who was a master tech for a car company did some electrical testing and that was the issue. Easy fix. $30 at West Marine for a new ignition.

Edit: by ignition - I mean the spot on your console where you insert the key. No one ever stick their head up in there to check those wires.

 

[TXJM]

Check the wires going into the ignition. If they are corroded or the ignition is corroded inside it then it won't complete the circuit. Think of it like an accidental kill switch getting pulled. Thats my guess since it dies like you are turning it off you said. It happened to me once and my buddy who was a master tech for a car company did some electrical testing and that was the issue. Easy fix. $30 at West Marine for a new ignition.

Edit: by ignition - I mean the spot on your console where you insert the key. No one ever stick their head up in there to check those wires.

An update. I believe it was a corroded battery connection. Cleaned all connections and it seems to start and run with out issue. It at least fixed my starting issue. We will see if the intermittent cutting out shows up again. The issue does act exactly like you suggest and I didn’t think of the kill circuit in the switch. Will check that if the problem show up again.
chip

 

[Smackdaddy53]

Those ground gremlins are crazy. Thanks for the update.

 

[17hpxt89]

Ground gremlin lol

 

[skinnydip]

i had this issue with mine and it was running lithium battery and pushing too much voltage shot it off. took forever to sort out. yamaha thought mine was vapor locking but it wasnt . there is screw you can get to with long handle flat head to vent it if it is vapor locking you will here it release when you turn it supposedly. wasnt my issue. make sure not electrical, yamaha alternators or more sensitive then tohatsu