I have a 2005 Yamaha 150, 4 stroke that will start sometimes and not at other times, I have new battery, the starter seems weak during the times it will not start but it seems strong next turn of the key. Do I need a new starter or is there something else causing this?

Sounds like the starter brushes or armature may be worn also you may have a corroded or loose wire somewhere between the battery and starter. Check inside the battery terminals for corrosion first.

Check the simple stuff first before condemning the starter. Usually a starter won't be good one time and bad the next. Check all connections from the battery to the outboard, including the ground. If that all checks, you can bypass the solenoid by using a heavy jumper wire and going from big post to big post of the solenoid. If when bypassing, starter still doesn't act right, then it's time to look at a possible rebuild of the starter. I do these here in Texarkana.
John

i had one that was used in saltwater an the battery cables broke down an would run the trim ok but wouldnt carry enough power to spin the motor over fast enough to start it good luck.

An easy way to test the battery cables is to do a load test at the starter solenoid. If you are'nt getting the amperage there, then the starter will not work properly. Which also means if your ignition system is battery operated, then it is not getting the voltage to activate the spark plugs. Hence. no start.

good info. guys, thanks, i will check everything said.
Thanks, Laine

ok , I have done/checked the following,
13 amps at solenoid when cranking,
wires clean at connections on both ends,
starter looks new (per shop mechanic),
new battery,

An electrician told me to change out ignition switch, maybe a bad connection.

Any ideas???

Thanks

That would be volts instead of amps but it is OK. Unless the mechanic took the starter apart, he can't tell you it "looks" new. If it hasn't been off, it's 6 to 7yrs old (2005 from previous post. I wouldn't change the ignition switch until I had someone go into the starter and check the brushes as well as the armature. The simple stuff I mentioned before seems to check out.
John