Yamaha F150 intermittent starting problem

nofishanywhere

Recruit
Joined
Feb 11, 2008
Messages
1
Have had this problem 3 times. Config: F150 with 2 batteries and Quest battery switch set to battery 1. Only accessory on is the Lowrance chartplotter.

Normal cold engine start, operate for an hour or so shutting down to fish, starting to move a few times and the last time the engine won?t start. With key to start position the starter won?t engage, barely audible click, engine instruments digits fade to off. With ignition ?on? (not start) the engine won?t tilt, engine instrument reads 7.4 VDC but starting battery reads 12.2 VDC measured at the battery terminals with a DVM. Also read 12.2 VDC at the starter solenoid on the engine. With ignition ?on? checked other accessories: horn is loud, bait and live well and bilge pumps are loud (normal). Same symptoms when switch to battery 2.

- First time this happened I pulled the 20 amp fuse for the starter, was ok, put it back in and engine operated normally, for a few outings.
- Second time I removed all the battery cables and 6 or so ground wires from common post, cleaned each. No change until carging the batteries. Ok for acouple of outings.
- Third time repeated checking cables with no change. Hooked up battery charger and monitored the engine instrument voltage. After only a couple of minutes the engine instrument voltage reading changed from 7.4 V\DC to 13.6 vdc and the engine operates normally. These readings are with all accessories off.

Reluctant to take it out again. At $95/hr labor cost I am also reluctant to take it into the dealer with things working "normally".

Have poured over the factory service manual. Can anyone explain how the engine instrument can read 7.4 vdc and votage at the battery terminals and on the engine at the starter solenoid is 12.2 vdc? What needs fixin?
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Yamaha F150 intermittent starting problem

you have a bad cable or cable connection.
was the boat rigged with the factory cables from yamaha or were they extended?
go by the dealership and ask for a copy of the voltage drop test.
or wait until someone will post it. I dont have time to explain it this morning due to the aggrevation with it at work yesterday.
but if the engine itself only saw 7.4 volts it would run nasty and most likly shut down as the fuel pump and ign system needs 9 volts just to stay powered up.
 
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