Yamaha 100hp 4 stroke just stops running 4200rpm

[kkilloy]

My son was using the boat today. He called and said that the boat just cut off when he was crusing 4200rpm as if the keyswitch was turned off. The engine will not turn over at all and the tilt/trim will not move. He said that the bilge pump and the depth find still work. The safety lanyard is in place, 1/2 tank of gas in the boat. The oil level is fine. No alarm buzzer sounded. The engine has already run 50 hours this season without a problem. I am going to tow the boat back to my place to work on it tomorrow. Any suggestions would be greatly appreciated.<br /><br />This is a great forum!<br /><br />Thanks,<br /><br />Kevin

 

[rodbolt]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

check the electrical connections at the battery, at the engine and make sure a cable did not get cut. also check the 20 amp ign fuse.sounds like the engine lost electrical power.

 

[kkilloy]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

Thanks Rodbolt, I will look at these and let you know what I find. Thanks for the help.<br /><br />Kevin

 

[kkilloy]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

I checked and the 30amp fuse was blown. I replaced the 30 amp fuse with the spare and I saw smoke right away, so I unplugged the fuse, it did not blow. I removed the covers from around the electronics and reinstalled the fuse so that I could see where the smoke was coming from. The rectifier/regulator is smoking. (part #67F-81960-11-00) Does this mean I can replace the rectifier/regulator and install a new fuse and I should be OK or do I need to look for something else?<br /><br />Thanks again,<br /><br />Kevin

 

[Ray Neudecker]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

That part will not normally blow on its own. Normally the cause is too much load on the system. I have seen it caused by using a deep cycle battery as a starting battery. Also as Rodbolt suggested you need to go over your connections between the battery and engine.

 

[kkilloy]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

I bite the bullet and bought a new regulator/rectifier at the yamaha dealer. ($225.00) I could have ordered it online for $166.00 but I really wanted it for this weekend. I bought a new marine starting battery and replaced the 30 amp fuse. Tilt works and it cranked right up and rode for several miles. I looked for bare wires, none seen. I hope there is not something else that will cause the new regulator to blow. The back of the damaged regulator I removed was burned. Thanks again for all the help getting me back on the water.<br /><br />Kevin

 

[alex3great]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

Hi,
I am having this same problem, except the engine would die at idle but run at with the fast idle up at higher rpm. The voltage reg/rec was smoking and burt the back and some of the insulation on the wires. Iam ordering a new voltage reg/rec, was there any damage to the stator or any other part? Do I have to worry about what caused the voltage reg/rec to burn out? any input would be appreciated.......Thanks;.l

 

[rodbolt]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

these regulater/rectifiers on larger motors can get hot. most now are either cooled by contact with the exhaust cover or the tell tale water.
I cant remember which models do what out of memory.
the biggest problem we have though is wing nuts on the battery(well sometimes loose nuts behind the helm ) .
anyway if your using wing nuts tighten them securly with pliers or even better swap them for the reccomended SS lock nuts.
loose or dirty connections can smoke a rectifier quickly.

 

[alex3great]

Re: Yamaha 100hp 4 stroke just stops running 4200rpm

Hi,
Thanks for the response. Do you think by tighten the battery wing nut and replacing the voltage regulator/rectifier the engine will be ok. I ran great up to this....Thanks again