Yamaha F150 Starting Problem

[sachin2021]

Hi.
My F150 developed a starting problem yesterday. Getting spark but won't start as it should. Finally managed to get it going after changing the primer bulb. Ran like a champ for a while and then coughed a bit and ran good. Put it back at the mooring and stopped and started and all was fine. Went back this afternoon and won't start. Could it be VST related. Motor has 850 hours and the VST filter has not been changed.

[boats.net]

Need to check fuel filters, condition of fuel, VST fuel pressure and fuel vacumn test at mechanical fuel pump.

[sachin2021]

OK. Will do that.

[sachin2021]

Would a weak battery cause the fuel pressure to drop?
Hooked up the GPS after the motor started this morning and ran for an hour. Voltage showed at 13.3V. Turned it off and voltage was at 12.8. Could not get it to start again.

[Bluefish]

Yes low voltage will cause these engines not to start check all connection on battery and engine and do a voltage drop test.

[sachin2021]

Saw 12.4 at the batteries and 12.4 at the starter motor. Upon cranking it drops to 4 volts at the starter but no go. Starter was also very hot to touch.

[TownsendsFJR1300]

Saw 12.4 at the batteries and 12.4 at the starter motor. Upon cranking it drops to 4 volts at the starter but no go. Starter was also very hot to touch.

If the voltage drops to 4 volts, get the battery load tested, it sounds like the battery is toast.

You can also try another battery for testing or jump starting with cables from another battery.

Any automotive store/Walmart can test it for free. If it passes, you need to look at the starter.

[sachin2021]

I have 2 batteries and this happens even when the selector switch is set to both. I will have a look at it though and have the starter serviced. I am all the way in the Fiji Islands and we do not have access to all the know how that you have in the US so to be able to get advice on the forum is really helpfull.

[99yam40]

Check voltage at the battery terminals also when loaded (cranking)to see it the voltage is dropping there also. Could be you have a bad cable that is not letting current flow as needed when loaded up( high resistance internally) and dropping voltage too much at motor

[sachin2021]

Thanks 99Yam. Will do that and look at the starter motor if all else checks out.

[sachin2021]

Also noticed that it will start and idle but if I give it even the slightest bit of throttle it cuts out. Also does this if I use the tilt motor. Suspect battery to motor cable problem.

[sachin2021]

Does the wire from the 30 amp fuse have any bearing on overall power to fuel pumps etc. Found corrosion in the fuse box

[sachin2021]

Thanks for all the help guys. Checked cleaned and where necessary changed all suspect wiring lugs. Charged batteries overnight to hold 13.2v.
Getting the same starting and cutting out problem.
Finally a friend suggested the ignition coil to spark plug connections may not be good.
Tightened the spark plug wires up and she started straight away and ran like a champ.

[99yam40]

Good to hear that it is starting and running well, but Hard to see how spark plug wires being loose fitting could cause voltage to drop to 4 volts at the starter like you said

[sachin2021]

Hi 99Yam. We also cleaned and where necessary put new lugs on positive and negative cables. The wire from the fuse box to the starter also had some issues and the 4V at the starter was after a prolonged period of attempted starts so all these factors would have played a part. The loose plug wire from the coil end was probably the most critical amongst a host of defects.